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Codeforces Round 1091 (Div. 2) and CodeCraft 26

Codeforces Round 1091 (Div. 2) and CodeCraft 26 Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 1000-2600 | Time: 7m 34s Problem Name Rating Tags Solve Time Verified B Flip the Bit (Easy Version) 1000 greedy, implementation 2m 15s ✗ D Flip the Bit (Hard Version) 1900 greedy, implementation, math 1m 50s ✗ E Definitely Larger 2000 binary-search, constructive-algorithms, data-structures 1m 39s ✗ G Down the...

Practice › Codeforces Solutions › Codeforces Round 1091 (Div. 2) and CodeCraft 26 ›

CF 2217E - Definitely Larger

CF 2217E - Definitely Larger Rating: 2000 Tags: binary search, constructive algorithms, data structures, graphs, greedy, sortings Solve time: 1m 39s Verified: no Solution Problem Understanding We are given a fixed permutation p of size n . Alongside it, we must construct another permutation q of the same size. The interaction between p and q defines a dominance relation: an index j is said to dominate an index i if...

Practice › Codeforces Solutions › Codeforces Round 1091 (Div. 2) and CodeCraft 26 ›

CF 2217D - Flip the Bit (Hard Version)

CF 2217D - Flip the Bit (Hard Version) Rating: 1900 Tags: greedy, implementation, math Solve time: 1m 50s Verified: no Solution Problem Understanding We are given a binary array where each position contains either 0 or 1. A subset of positions is marked as special, and all special positions initially share the same value, call it $x$. The goal is to transform the entire array so that every element becomes...

Practice › Codeforces Solutions › Codeforces Round 1091 (Div. 2) and CodeCraft 26 ›

CF 2217B - Flip the Bit (Easy Version)

CF 2217B - Flip the Bit (Easy Version) Rating: 1000 Tags: greedy, implementation Solve time: 2m 15s Verified: no Solution Problem Understanding We are given a binary array of length n and a single special index p (since k=1 in this easy version). The bit at this index is considered "correct," and the goal is to make the entire array equal to this bit by performing the fewest number of...

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Codeforces Round 1090 (Div. 4)

Codeforces Round 1090 (Div. 4) Type: Div. 4 | Problems: 4 | Verified: 1/4 | Rating range: 800-1800 | Time: 10m 7s Problem Name Rating Tags Solve Time Verified A The 67th Integer Problem 800 brute-force, games, implementation 1m 27s ✓ D The 67th OEIS Problem 1100 constructive-algorithms, greedy, math 2m 4s ✗ F The 67th Tree Problem 1500 constructive-algorithms, implementation, trees 3m 38s ✗ G [The 67th Iteration of...

Practice › Codeforces Solutions › Codeforces Round 1090 (Div. 4) ›

CF 2218D - The 67th OEIS Problem

CF 2218D - The 67th OEIS Problem Rating: 1100 Tags: constructive algorithms, greedy, math, number theory Solve time: 2m 4s Verified: no Solution Problem Understanding We are asked to construct sequences of integers of length $n$ such that the greatest common divisor (gcd) of consecutive elements is always distinct. Each test case provides a number $n$, and for each, we must output one valid sequence of length $n$. The output...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.14 Graph Greedy

14.14 Graph Greedy Many of the most successful graph algorithms are greedy algorithms. At first glance, this may seem surprising. Graphs contain complex global structure. A local decision on one edge can affect paths, connectivity, cycles, and costs throughout the entire graph. Yet some graph problems possess exactly the structural properties that greedy algorithms require. In these cases, local choices can be proven safe through cut properties, exchange arguments, or...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.22 Greedy Algorithm Design Checklist

14.22 Greedy Algorithm Design Checklist Throughout this chapter, we have studied a wide variety of greedy algorithms: Interval scheduling Activity selection Huffman coding Fractional knapsack Job sequencing Minimum refueling stops Course scheduling Graph optimization String optimization Resource allocation At first glance, these algorithms appear unrelated. They operate on different data structures, optimize different objectives, and use different proof techniques. Yet successful greedy algorithms are usually discovered through the same design...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.3 Matroids Overview

14.3 Matroids Overview Many greedy algorithms appear unrelated on the surface. Selecting activities, building minimum spanning trees, choosing independent edges, and constructing certain optimal subsets seem like completely different problems. Yet a common mathematical structure lies beneath them. That structure is called a matroid. Matroids provide one of the deepest explanations for why greedy algorithms work. They identify an entire class of optimization problems where a simple greedy strategy is...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.10 Prefix Constraints

14.10 Prefix Constraints Many greedy algorithms operate under a simple principle: A decision is either feasible or infeasible. Prefix-constrained problems are more subtle. A decision that appears feasible now may create an infeasible state later. The challenge is maintaining feasibility not only for the final solution but for every prefix of the construction process. These problems appear in scheduling, streaming systems, bandwidth allocation, project planning, load balancing, and resource management....

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.12 Priority Queue Greedy

14.12 Priority Queue Greedy Many greedy algorithms appear different on the surface. One schedules jobs, another allocates resources, another computes shortest paths, and another determines refueling stops. Yet a surprising number share the same implementation pattern: Repeatedly select the best available candidate. The challenge is maintaining the set of candidates efficiently. A priority queue solves this problem. Instead of repeatedly scanning all possibilities, the algorithm maintains candidates in a structure...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.17 Greedy Data Structure Design

14.17 Greedy Data Structure Design Many greedy algorithms are remembered by their choice rule: Choose the earliest finishing interval. Choose the highest-density item. Choose the cheapest edge. Choose the largest available fuel station. In practice, however, the success of a greedy algorithm often depends just as much on the supporting data structure as on the greedy rule itself. A theoretically correct greedy strategy can become unusable if each decision requires...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.26 Chapter Summary

14.26 Chapter Summary Greedy algorithms are among the most elegant techniques in algorithm design. They solve complex optimization problems through a sequence of simple decisions: Choose the best option now. Commit immediately. Never reconsider. At first, this approach seems risky. Most optimization problems involve many interacting choices, and a poor early decision can easily destroy optimality. Yet certain problems possess hidden structure that makes local decisions surprisingly powerful. When that...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.13 Two-Pointer Greedy

14.13 Two-Pointer Greedy Many greedy algorithms operate on sorted data and repeatedly make decisions from the extremes of a range. Instead of maintaining a complex state or exploring multiple possibilities, the algorithm keeps two indices and moves one of them after each decision. This pattern is known as the two-pointer technique. While two pointers are often introduced as an array-processing optimization, they also form the basis of several elegant greedy...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.11 Sorting Plus Greedy

14.11 Sorting Plus Greedy Many greedy algorithms begin with a sort. The sort is not an implementation detail. It is often the step that exposes the structure needed for the greedy rule to work. Without sorting, a greedy algorithm may see decisions in an arbitrary order and make choices before it has enough context. With sorting, the algorithm processes candidates according to the property that matters: finish time, deadline, profit,...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.7 Fractional Knapsack

14.7 Fractional Knapsack The fractional knapsack problem is one of the clearest examples of a greedy algorithm producing an optimal solution. Unlike many optimization problems where local decisions can lead to poor global outcomes, fractional knapsack possesses a structure that makes the greedy choice immediately obvious once the correct perspective is adopted. The problem is important for two reasons. First, it demonstrates a powerful exchange argument. Second, it provides a...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.1 Greedy Choice Property

14.1 Greedy Choice Property The greedy choice property is the fundamental condition that allows a greedy algorithm to produce an optimal solution. Informally, it states that there exists an optimal solution whose first decision matches the decision selected by the greedy algorithm. Once this decision is fixed, the remaining problem can be solved independently using the same reasoning. Every successful greedy algorithm relies on this property. Without it, a locally...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.8 Job Sequencing with Deadlines

14.8 Job Sequencing with Deadlines Many scheduling problems ask a simple question: Given limited time and many competing jobs, which jobs should be performed? The answer is rarely "perform all of them." Deadlines, resource constraints, and limited execution windows force choices. The objective becomes selecting the subset that produces the greatest overall benefit. The Job Sequencing with Deadlines problem is a classic example. Each job requires one unit of time,...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.5 Activity Selection

14.5 Activity Selection The activity selection problem is historically one of the first optimization problems used to demonstrate the power of greedy algorithms. Although it is mathematically equivalent to interval scheduling, it deserves separate study because it introduces a broader design pattern: When resources are limited and tasks compete for those resources, selecting the task that leaves the most flexibility for future decisions often leads to an optimal solution. This...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.16 String Greedy

14.16 String Greedy String problems often invite dynamic programming, tries, automata, and hashing. But a substantial class of string problems has a simpler structure: decisions can be made greedily from left to right, from right to left, or from a stack-maintained frontier. The difficulty is recognizing when a character decision is permanent. A greedy string algorithm usually depends on a monotonic property: once a character is placed, removed, or skipped,...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.9 Minimum Refueling Stops

14.9 Minimum Refueling Stops Minimum refueling stops is a greedy scheduling problem disguised as a travel problem. You are given a target distance, an initial amount of fuel, and a list of fuel stations along the route. The goal is to reach the destination while stopping as few times as possible. The problem is useful because the greedy choice is not "stop at the nearest station" or "always fill when...

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Chapter 14. Greedy Algorithms

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.2 Exchange Arguments

14.2 Exchange Arguments Most greedy algorithms are not proved by directly showing that the greedy solution is optimal. Instead, they are proved using an exchange argument. This technique starts with an arbitrary optimal solution and gradually transforms it into the greedy solution without reducing its quality. If every transformation preserves optimality, the greedy solution must also be optimal. Exchange arguments are the primary proof technique in greedy algorithm design. They...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.19 Counterexamples

14.19 Counterexamples A counterexample is a small input that disproves a proposed algorithm, lemma, or proof idea. In greedy algorithm design, counterexamples are especially valuable because many greedy rules look plausible before they are tested. A good counterexample does more than show that an algorithm is wrong. It explains why the greedy choice is wrong. It reveals which local score is misleading, which constraint was ignored, or which exchange argument...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.18 Local vs Global Optimum

14.18 Local vs Global Optimum Greedy algorithms are attractive because they make local decisions. At each step, the algorithm chooses the best-looking option available at that moment and commits to it. When the problem has the right structure, those local choices accumulate into a globally optimal solution. When the structure is absent, greedy algorithms fail. This distinction is central to greedy design. A local optimum is the best choice within...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.15 Greedy Scheduling Patterns

14.15 Greedy Scheduling Patterns Scheduling problems occupy a special place in algorithm design. Many of the earliest greedy algorithms were developed for scheduling, and many modern scheduling systems continue to rely on greedy principles. The reason is structural. Scheduling problems naturally involve competition for limited resources: Time Machines CPUs Workers Network bandwidth Storage Transportation capacity When resources are scarce, choices must be made. Greedy algorithms often succeed because they preserve...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.4 Interval Scheduling

14.4 Interval Scheduling Interval scheduling is one of the most important greedy problems. It is often the first example where a greedy algorithm achieves a globally optimal solution while remaining remarkably simple. The problem appears in operating systems, conference room allocation, CPU scheduling, manufacturing pipelines, booking systems, airline gate assignment, and project planning. Although the applications differ, the mathematical structure remains identical: choose as many non-overlapping intervals as possible. This...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.25 Exercises

14.25 Exercises Greedy algorithms are best learned by proving, breaking, and implementing them. The code is usually short. The reasoning is where the work happens. This final section collects exercises that reinforce the patterns from the chapter. Each problem asks you to identify the greedy choice, justify it, implement it, and analyze the result. Several exercises also ask for counterexamples, because a strong greedy designer must know how to disprove...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.6 Huffman Coding

14.6 Huffman Coding Huffman coding is one of the most successful greedy algorithms ever developed. It is used in file compression, image formats, audio codecs, archive utilities, network protocols, and countless data storage systems. Unlike activity scheduling, which optimizes the number of selected intervals, Huffman coding optimizes the representation of information itself. Given a set of symbols and their frequencies, the goal is to construct a binary encoding that minimizes...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.20 Proving Greedy Algorithms

14.20 Proving Greedy Algorithms Designing a greedy algorithm is often easier than proving it correct. Many rules appear reasonable: Choose the earliest interval. Choose the cheapest edge. Choose the largest coin. Choose the highest-value item. Some of these rules are optimal. Others fail spectacularly. The difference is not in the implementation. The difference is in the proof. This chapter concludes the study of greedy algorithms by focusing on correctness proofs....

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.21 Complexity Analysis

14.21 Complexity Analysis Greedy algorithms often have simple control flow. Sort the input, scan once, push into a heap, pop from a heap, or union two components. Because the code is usually compact, it is tempting to assume the complexity is obvious. That assumption is risky. The cost of a greedy algorithm is usually hidden in the supporting operation: Sort Heap push Heap pop Find Union Tree lookup Stack update...

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.23 Case Studies

14.23 Case Studies Greedy algorithms become easier to recognize after seeing them embedded in complete problems. A textbook description often isolates the core idea, but real use cases include input modeling, edge cases, implementation constraints, and proof obligations. This recipe walks through several compact case studies. Each one follows the same structure: Model the problem. Identify the greedy choice. Choose the supporting data structure. Prove why the choice is safe....

Programming › Algorithm Cookbook › Chapter 14. Greedy Algorithms ›

14.24 Advanced Greedy Techniques

14.24 Advanced Greedy Techniques The classical greedy algorithms presented earlier in this chapter are often introduced as isolated ideas: Interval scheduling Huffman coding Fractional knapsack Kruskal's algorithm Dijkstra's algorithm As problems become more sophisticated, however, greedy solutions rarely appear in such a pure form. Instead, they combine multiple techniques: Sorting plus heaps Greedy plus binary search Greedy plus graph traversal Greedy plus dynamic maintenance Greedy plus amortized analysis This chapter...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227D - Palindromex

CF 2227D - Palindromex Rating: - Tags: binary search, brute force, constructive algorithms, data structures, greedy, implementation, two pointers Solve time: 3m 24s Verified: no Solution Problem Understanding We are given an array of length $2n$. Every value from $0$ to $n-1$ appears exactly twice. The task is to select a contiguous segment of this array that reads the same left-to-right and right-to-left, and among all such segments we want...

Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225B - Alternating String

CF 2225B - Alternating String Rating: - Tags: brute force, greedy Solve time: 3m 12s Verified: no Solution Problem Understanding We are given a binary string made of only a and b . The goal is to check whether we can turn it into a perfectly alternating string, meaning every adjacent pair of characters differs. We are allowed to perform at most one operation. In that operation we pick a...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227E - It All Went Sideways

CF 2227E - It All Went Sideways Rating: - Tags: binary search, data structures, dp, greedy Solve time: 2m 57s Verified: no Solution Problem Understanding Each test case gives a sequence of column heights. Think of column i as a vertical stack of unit blocks, occupying rows 1 up to a_i . All blocks in a row are aligned across columns. Then gravity is suddenly redefined: instead of falling down,...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226E - Mental Monumental (Hard Version)

CF 2226E - Mental Monumental (Hard Version) Rating: - Tags: data structures, greedy, math, two pointers Solve time: 3m 59s Verified: no Solution Problem Understanding We are given an array, and we look at it prefix by prefix. For each prefix we are allowed to transform each element independently exactly once using a very permissive operation: pick any integer $b_i \ge 1$, replace $a_i$ with the remainder of dividing it...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227F - It Just Keeps Going Sideways

CF 2227F - It Just Keeps Going Sideways Rating: - Tags: binary search, data structures, dp, greedy, math Solve time: 5m 5s Verified: no Solution Problem Understanding Each column contains cubes stacked from height $1$ up to height $a_i$. After gravity turns to the right, cubes never change height. Cubes at the same height slide independently and occupy the rightmost available positions on that horizontal level. It is useful to...

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Codeforces Round 1095 (Div. 2)

Codeforces Round 1095 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 0/7 | Rating range: - | Time: 23m 23s Problem Name Rating Tags Solve Time Verified A Disturbing Distribution - greedy, math 3m 10s ✗ B Everything Everywhere - greedy, math, number-theory 3m 22s ✗ C Mental Monumental (Easy Version) - binary-search, data-structures, greedy 6m 17s ✗ D Reserved Reversals - constructive-algorithms, dp, greedy 2m 22s ✗...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226A - Disturbing Distribution

CF 2226A - Disturbing Distribution Rating: - Tags: greedy, math Solve time: 3m 10s Verified: no Solution Problem Understanding We are given a sequence of positive integers. We repeatedly remove groups of elements until nothing remains. Each group must respect two constraints: if we look at the chosen indices in increasing order, the corresponding values must be nondecreasing, and the indices themselves must be strictly increasing as usual for a...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226B - Everything Everywhere

CF 2226B - Everything Everywhere Rating: - Tags: greedy, math, number theory Solve time: 3m 22s Verified: no Solution Problem Understanding We are given a permutation of the integers from 1 to n . For every contiguous subarray, we look at three quantities: its maximum value, its minimum value, the GCD of all values inside it. A subarray is called good when $$\max - \min = \gcd(\text{all elements})$$ The task...

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Educational Codeforces Round 189 (Rated for Div. 2)

Educational Codeforces Round 189 (Rated for Div. 2) Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: - | Time: 14m 18s Problem Name Rating Tags Solve Time Verified B Alternating String - brute-force, greedy 3m 12s ✗ C Red-Black Pairs - dp, greedy 2m 34s ✗ D Exceptional Segments - bitmasks, brute-force, math 3m 1s ✗ E Covering Points with Circles - constructive-algorithms, geometry, math 2m...

Practice › Codeforces Solutions › Codeforces Round 1096 (Div. 3) ›

CF 2227B - Party Monster

CF 2227B - Party Monster Rating: - Tags: greedy Solve time: 3m 38s Verified: no Solution Problem Understanding We are given a string made only of opening and closing parentheses. In one move, we are allowed to take a contiguous block, remove it, and then reinsert its characters anywhere in the remaining string, with full freedom to permute those removed characters and place each one independently. The question is whether,...

Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225F - String Cutting

CF 2225F - String Cutting Rating: - Tags: binary search, brute force, greedy, hashing, string suffix structures, strings Solve time: 2m 54s Verified: no Solution Problem Understanding A string $s$ must be split into several contiguous pieces. Each piece has length at least $l$, and the total number of pieces is at least $k$. After cutting, all pieces are sorted lexicographically, and the piece in position $k$ of this sorted...

Practice › Codeforces Solutions › Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2) ›

CF 2222B - Artistic Balance Tree

CF 2222B - Artistic Balance Tree Rating: - Tags: greedy, sortings Solve time: 3m 53s Verified: no Solution Problem Understanding We have an array, and before each marking operation we are allowed to reverse any odd-length segment centered at some position. After that reversal, the element currently sitting at index x_i becomes marked. The subtle detail is that marks belong to elements, not positions. If an element gets marked and...

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Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2)

Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 6 | Verified: 0/6 | Rating range: - | Time: 23m 39s Problem Name Rating Tags Solve Time Verified A A Wonderful Contest - brute-force, dp, math 4m 29s ✗ B Artistic Balance Tree - greedy, sortings 3m 53s ✗ C Median Partition - dp, math 2m 36s ✗ D Permutation Construction -...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226D - Reserved Reversals

CF 2226D - Reserved Reversals Rating: - Tags: constructive algorithms, dp, greedy, math Solve time: 2m 22s Verified: no Solution Problem Understanding We are given several test cases, each consisting of an array. The task is to decide whether we can transform each array into a non-decreasing order using a specific operation: we may pick any subarray, compute its minimum and maximum values, and reverse it, but only if the...

Practice › Codeforces Solutions › Codeforces Round 1095 (Div. 2) ›

CF 2226C - Mental Monumental (Easy Version)

CF 2226C - Mental Monumental (Easy Version) Rating: - Tags: binary search, data structures, greedy, math, two pointers Solve time: 6m 17s Verified: no Solution Problem Understanding Each array element can be modified independently. For a value $x$, we may choose any positive integer $b$, then replace $x$ by $x \bmod b$. The goal is to maximize the MEX of the resulting array. Since the operation is applied independently to...

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Codeforces Round 1096 (Div. 3)

Codeforces Round 1096 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 0/8 | Rating range: - | Time: 27m 59s Problem Name Rating Tags Solve Time Verified A Koshary - implementation, math 2m 38s ✗ B Party Monster - greedy 3m 38s ✗ C Snowfall - constructive-algorithms, math 4m 24s ✗ D Palindromex - binary-search, brute-force, constructive-algorithms 3m 24s ✗ E It All Went Sideways - binary-search, data-structures,...

Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225C - Red-Black Pairs

CF 2225C - Red-Black Pairs Rating: - Tags: dp, greedy Solve time: 2m 34s Verified: no Solution Problem Understanding We are given a grid with $2$ rows and $n$ columns. Each cell is initially colored either red or black. We are allowed to repaint any cells, and the goal is to reach a final coloring with the following property: the entire $2n$ cells can be partitioned into exactly $n$ disjoint...

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LeetCode 3675 - Minimum Operations to Transform String

LeetCode Problem 3675 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding We are given a string s consisting of lowercase English letters. An operation chooses a character value c and simultaneously replaces every occurrence of c in the current string with the next letter of the alphabet. The alphabet is circular, so 'z' becomes 'a' . The important detail is that an operation acts on a letter value, not...

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LeetCode 3633 - Earliest Finish Time for Land and Water Rides I

LeetCode Problem 3633 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the earliest possible time a tourist can finish exactly one land ride and one water ride at a theme park, where rides may be taken in either order. Each ride has a start time , representing when it becomes available, and a duration , representing how long...

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LeetCode 3600 - Maximize Spanning Tree Stability with Upgrades

LeetCode Problem 3600 Difficulty: 🔴 Hard Topics: Binary Search, Greedy, Union-Find, Graph Theory, Minimum Spanning Tree Solution Problem Understanding This problem asks us to determine the maximum possible stability of a spanning tree built from a weighted, undirected graph with certain constraints. Each edge in the graph has a strength and a mandatory flag . A mandatory edge ( musti == 1 ) must appear in the spanning tree, and...

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LeetCode 3576 - Transform Array to All Equal Elements

LeetCode Problem 3576 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem is asking whether it is possible to transform an array nums consisting of only 1 and -1 into an array where all elements are equal, by performing at most k operations. Each operation allows you to select an index i and flip the signs of both nums[i] and nums[i+1] . The key aspect is that you...

Practice › Codeforces Solutions › Codeforces Round 941 (Div. 2) ›

CF 1966A - Card Exchange

CF 1966A - Card Exchange Rating: 800 Tags: constructive algorithms, games, greedy Solve time: 1m 12s Verified: no Solution Problem Understanding We are given a multiset of cards, where each card carries an integer label. The only allowed operation takes exactly k cards that all share the same label and removes them, replacing them with k-1 new cards whose labels we are free to choose arbitrarily. The freedom to assign...

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956D - Nene and the Mex Operator

CF 1956D - Nene and the Mex Operator Rating: 2000 Tags: bitmasks, brute force, constructive algorithms, divide and conquer, dp, greedy, implementation, math Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a short array of length at most 18. The only allowed move is to pick a contiguous segment, compute the mex of that segment, and overwrite the entire segment with that mex value. This operation...

Practice › Codeforces Solutions › Codeforces Round 942 (Div. 1) ›

CF 1967A - Permutation Counting

CF 1967A - Permutation Counting Rating: 1400 Tags: binary search, greedy, implementation, math, sortings Solve time: 1m 16s Verified: no Solution Problem Understanding We are given a set of cards, each labeled with a number from 1 to n. For each number i, we have a_i cards of that type. We also have k coins, and each coin allows us to buy a new card of any type, so we...

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Codeforces Round 934 (Div. 2)

Codeforces Round 934 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1100 | Time: 2m 14s Problem Name Rating Tags Solve Time Verified A Destroying Bridges 800 graphs, greedy, math 55s ✓ B Equal XOR 1100 bitmasks, constructive-algorithms 1m 19s ✗

Practice › Codeforces Solutions › CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) ›

CF 1942C1 - Bessie's Birthday Cake (Easy Version)

CF 1942C1 - Bessie's Birthday Cake (Easy Version) Rating: 1300 Tags: geometry, greedy, math Solve time: 56s Verified: yes Solution Problem Understanding We are given a regular polygon with $n$ vertices representing a cake. Some vertices are already selected by Bessie as potential endpoints for drawing diagonals. Each diagonal connects two chosen vertices, and the goal is to maximize the number of triangles formed by non-intersecting diagonals among these selected...

Practice › Codeforces Solutions › Codeforces Round 937 (Div. 4) ›

CF 1950F - 0, 1, 2, Tree!

CF 1950F - 0, 1, 2, Tree! Rating: 1700 Tags: bitmasks, brute force, greedy, implementation, trees Solve time: 1m Verified: no Solution Problem Understanding We are asked to construct a rooted tree with a specific number of vertices having 0, 1, or 2 children. The input gives three numbers: a vertices with 2 children, b vertices with 1 child, and c vertices that are leaves. The task is to determine...

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956C - Nene's Magical Matrix

CF 1956C - Nene's Magical Matrix Rating: 1600 Tags: constructive algorithms, greedy, math Solve time: 57s Verified: yes Solution Problem Understanding We are given a square matrix of size $n \times n$ initially filled with zeroes. Nene can perform two types of operations: either set an entire row to a permutation of $1$ through $n$ or set an entire column to such a permutation. The goal is to maximize the...

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Codeforces Round 940 (Div. 2) and CodeCraft-23

Codeforces Round 940 (Div. 2) and CodeCraft-23 Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1100 | Time: 4m 40s Problem Name Rating Tags Solve Time Verified A Stickogon 800 constructive-algorithms, greedy 43s ✓ B A BIT of a Construction 1100 bitmasks, constructive-algorithms, greedy 3m 57s ✗

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946C - Tree Cutting

CF 1946C - Tree Cutting Rating: 1600 Tags: binary search, dp, greedy, implementation, trees Solve time: 2m 50s Verified: yes Solution Problem Understanding We are given a tree with $n$ vertices, which is a connected graph without cycles. The task is to remove exactly $k$ edges from this tree and determine the largest integer $x$ such that each resulting connected component has at least $x$ vertices. In simpler terms, we...

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976E - Splittable Permutations

CF 1976E - Splittable Permutations Rating: 2500 Tags: combinatorics, data structures, dfs and similar, greedy, math, trees Solve time: 5m 16s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 275 (Div. 1) ›

CF 482A - Diverse Permutation

CF 482A - Diverse Permutation Rating: 1200 Tags: constructive algorithms, greedy Solve time: 11m 3s Verified: no Solution Problem Understanding We are asked to construct a permutation of integers from 1 to n such that the set of absolute differences between consecutive elements contains exactly k distinct values. Concretely, if the permutation is [p1, p2, ..., pn] , then the list [|p1 - p2|, |p2 - p3|, ..., |pn-1 -...

Practice › Codeforces Solutions › Codeforces Round 946 (Div. 3) ›

CF 1974A - Phone Desktop

CF 1974A - Phone Desktop Rating: 800 Tags: greedy, math Solve time: 5m 17s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 946 (Div. 3) ›

CF 1974G - Money Buys Less Happiness Now

CF 1974G - Money Buys Less Happiness Now Rating: 2000 Tags: data structures, greedy, sortings Solve time: 5m 13s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 945 (Div. 2) ›

CF 1973B - Cat, Fox and the Lonely Array

CF 1973B - Cat, Fox and the Lonely Array Rating: 1300 Tags: binary search, bitmasks, data structures, greedy, math, two pointers Solve time: 5m 16s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951F - Inversion Composition

CF 1951F - Inversion Composition Rating: 2500 Tags: constructive algorithms, data structures, greedy Solve time: 1m 56s Verified: no Solution Problem Understanding We are asked to construct a permutation q of size n such that the sum of inversions of q and the composition q ∘ p equals a given target k . The input permutation p is fixed, and inversions count how many pairs of indices are out of...

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951I - Growing Trees

CF 1951I - Growing Trees Rating: 3200 Tags: binary search, constructive algorithms, flows, graphs, greedy Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a connected simple undirected graph with up to 50 vertices and at most 50 edges. Each edge can be used multiple times in a constructed multigraph, and we control how many copies of each edge we create through a non-negative integer array $x$....

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975A - Bazoka and Mocha's Array

CF 1975A - Bazoka and Mocha's Array Rating: 800 Tags: brute force, greedy, implementation, sortings Solve time: 5m 18s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975D - Paint the Tree

CF 1975D - Paint the Tree Rating: 1700 Tags: brute force, dfs and similar, dp, greedy, shortest paths, trees Solve time: 5m 19s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 940 (Div. 2) and CodeCraft-23 ›

CF 1957B - A BIT of a Construction

CF 1957B - A BIT of a Construction Rating: 1100 Tags: bitmasks, constructive algorithms, greedy, implementation Solve time: 3m 57s Verified: no Solution Problem Understanding We are asked to construct a sequence of n non-negative integers that sum to a given value k , while maximizing the number of distinct 1 bits in the binary representation of their bitwise OR. In other words, we are free to distribute k across...

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951D - Buying Jewels

CF 1951D - Buying Jewels Rating: 2000 Tags: constructive algorithms, greedy, math Solve time: 1m 19s Verified: no Solution Problem Understanding We are given a buyer who starts with a fixed number of coins. A shop is not fixed in advance; instead, we are allowed to design up to 60 sequential stalls. Each stall has an unlimited supply of jewels, and a fixed integer price per jewel. The buyer behaves...

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976F - Remove Bridges

CF 1976F - Remove Bridges Rating: 2800 Tags: data structures, dfs and similar, dp, greedy, sortings, trees Solve time: 5m 17s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955C - Inhabitant of the Deep Sea

CF 1955C - Inhabitant of the Deep Sea Rating: 1300 Tags: greedy, implementation, math Solve time: 1m 10s Verified: no Solution Problem Understanding We are given a line of ships, each with some durability, and a fixed attack pattern that always targets the current leftmost surviving ship, then the current rightmost surviving ship, and repeats this alternation until a total of $k$ attacks have been made or all ships sink....

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956E2 - Nene vs. Monsters (Hard Version)

CF 1956E2 - Nene vs. Monsters (Hard Version) Rating: 2700 Tags: brute force, greedy, implementation, math Solve time: 1m 1s Verified: no Solution Problem Understanding We are given a circle of monsters, each with an energy level. The monsters attack their neighbor in a fixed clockwise order: monster 1 attacks monster 2, monster 2 attacks monster 3, and so on, with the last monster attacking the first. The attack reduces...

Practice › Codeforces Solutions › Codeforces Round 279 (Div. 2) ›

CF 490E - Restoring Increasing Sequence

CF 490E - Restoring Increasing Sequence Rating: 2000 Tags: binary search, brute force, greedy, implementation Solve time: 10m 45s Verified: no Solution Problem Understanding We are given a sequence of positive integers written on the board, but some of the digits have been replaced by question marks. Each question mark represents a lost digit, so our task is to restore the sequence to a strictly increasing list of positive integers....

Practice › Codeforces Solutions › European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) ›

CF 1949B - Charming Meals

CF 1949B - Charming Meals Rating: 1500 Tags: binary search, brute force, greedy, sortings Solve time: 1m 44s Verified: yes Solution Problem Understanding We have two arrays of size n . The array a contains the spiciness values of the appetizers, and the array b contains the spiciness values of the main dishes. Every appetizer must be paired with exactly one main dish, and every main dish must be used...

Practice › Codeforces Solutions › Codeforces Round 935 (Div. 3) ›

CF 1945D - Seraphim the Owl

CF 1945D - Seraphim the Owl Rating: 1300 Tags: dp, greedy Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given a queue of n people waiting to ask Seraphim the Owl a question. Kirill arrives at the end of the line and wants to move forward so that he is among the first m people. To move forward, he can swap with someone ahead in the queue,...

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 1) ›

CF 1943C - Tree Compass

CF 1943C - Tree Compass Rating: 2300 Tags: constructive algorithms, dfs and similar, greedy, trees Solve time: 1m 16s Verified: no Solution Problem Understanding We are given a tree and an operation that does not act on a single node, but on a layer of nodes: if we pick a center vertex $v$ and a distance $d$, we recolor every vertex whose shortest-path distance from $v$ is exactly $d$. Each...

Practice › Codeforces Solutions › Educational Codeforces Round 164 (Rated for Div. 2) ›

CF 1954A - Painting the Ribbon

CF 1954A - Painting the Ribbon Rating: 900 Tags: constructive algorithms, greedy, math Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to decide whether Alice can paint a ribbon of n parts using m colors such that Bob, who can repaint at most k parts into the same color, cannot make the entire ribbon monochromatic. Alice has full freedom to choose the initial coloring, while Bob...

Practice › Codeforces Solutions ›

Educational Codeforces Round 164 (Rated for Div. 2)

Educational Codeforces Round 164 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 2/6 | Rating range: 900-3100 | Time: 7m 33s Problem Name Rating Tags Solve Time Verified A Painting the Ribbon 900 constructive-algorithms, greedy, math 1m 3s ✓ B Make It Ugly 1200 implementation, math 1m 15s ✗ C Long Multiplication 1200 greedy, math, number-theory 1m 13s ✗ D Colored Balls 1800 combinatorics, dp, math...

Practice › Codeforces Solutions › Codeforces Round 276 (Div. 1) ›

CF 484D - Kindergarten

CF 484D - Kindergarten Rating: 2400 Tags: data structures, dp, greedy Solve time: 5m 17s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 935 (Div. 3) ›

CF 1945E - Binary Search

CF 1945E - Binary Search Rating: 1700 Tags: binary search, constructive algorithms, greedy Solve time: 1m 21s Verified: no Solution Problem Understanding We are given a permutation of size $n$, meaning every number from $1$ to $n$ appears exactly once, but in some arbitrary order. Along with it, we are given a target value $x$ that definitely exists somewhere in the array. We are allowed to perform at most two...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946D - Birthday Gift

CF 1946D - Birthday Gift Rating: 1900 Tags: bitmasks, brute force, constructive algorithms, greedy, implementation Solve time: 1m 7s Verified: no Solution Problem Understanding We are given an array and we are allowed to split it into a sequence of contiguous segments. Each segment is evaluated by taking the bitwise XOR of its elements. Once all segment XORs are computed, we combine those results using bitwise OR, left to right...

Practice › Codeforces Solutions ›

Codeforces Round 947 (Div. 1 + Div. 2)

Codeforces Round 947 (Div. 1 + Div. 2) Type: Div. 1+2 | Problems: 9 | Verified: 0/9 | Rating range: 800-3500 | Time: 47m 41s Problem Name Rating Tags Solve Time Verified A Bazoka and Mocha's Array 800 brute-force, greedy, implementation 5m 18s ✗ B 378QAQ and Mocha's Array 1000 brute-force, greedy, math 5m 18s ✗ C Chamo and Mocha's Array 1200 binary-search, brute-force, greedy 5m 19s ✗ D Paint...

Practice › Codeforces Solutions › Codeforces Round 280 (Div. 2) ›

CF 492C - Vanya and Exams

CF 492C - Vanya and Exams Rating: 1400 Tags: greedy, sortings Solve time: 57s Verified: yes Solution Problem Understanding Vanya has a number of exams, each graded between 1 and a maximum score r . He wants his overall average to reach at least avg to qualify for a scholarship. For each exam, he can improve his score by writing essays, with the cost of increasing a grade by 1...

Practice › Codeforces Solutions › Codeforces Round 940 (Div. 2) and CodeCraft-23 ›

CF 1957A - Stickogon

CF 1957A - Stickogon Rating: 800 Tags: constructive algorithms, greedy Solve time: 43s Verified: yes Solution Problem Understanding We are given a collection of sticks, each with an integer length. The goal is to build as many regular polygons as possible using these sticks, with the restriction that each side of a polygon must be exactly one stick, and no stick can be reused. A regular polygon requires at least...

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 1) ›

CF 1943A - MEX Game 1

CF 1943A - MEX Game 1 Rating: 1300 Tags: games, greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We are asked to analyze a two-player game on an array of non-negative integers. Alice begins with an empty array c , and on her turn, she takes any element from the initial array a and appends it to c . Bob, on his turn, removes any element from a...

Practice › Codeforces Solutions ›

Codeforces Round 934 (Div. 1)

Codeforces Round 934 (Div. 1) Type: Div. 1 | Problems: 8 | Verified: 1/8 | Rating range: 1300-3500 | Time: 10m 17s Problem Name Rating Tags Solve Time Verified A MEX Game 1 1300 games, greedy 1m 9s ✓ B Non-Palindromic Substring 2000 hashing, implementation, math 1m 20s ✗ C Tree Compass 2300 constructive-algorithms, dfs-and-similar, greedy 1m 16s ✗ D1 Counting Is Fun (Easy Version) 2400 brute-force, combinatorics, dp 1m...

Practice › Codeforces Solutions ›

Codeforces Round 277 (Div. 2)

Codeforces Round 277 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 800-2200 | Time: 26m 47s Problem Name Rating Tags Solve Time Verified A Calculating Function 800 implementation, math 10m 49s ✗ B OR in Matrix 1300 greedy, hashing, implementation 5m 23s ✗ D Valid Sets 2100 dfs-and-similar, dp, math 5m 18s ✗ E LIS of Sequence 2200 data-structures, dp, greedy 5m 17s ✗

Practice › Codeforces Solutions › Codeforces Round 941 (Div. 1) ›

CF 1965A - Everything Nim

CF 1965A - Everything Nim Rating: 1400 Tags: games, greedy, math, sortings Solve time: 1m 24s Verified: no Solution Problem Understanding We are given several independent games, each defined by a list of piles containing stones. Two players alternate turns. A move consists of choosing an integer $k$ that does not exceed the smallest nonempty pile, then simultaneously subtracting $k$ stones from every pile that is still nonempty. Any pile...

Practice › Codeforces Solutions › European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) ›

CF 1949G - Scooter

CF 1949G - Scooter Rating: 2300 Tags: graphs, greedy Solve time: 3m 15s Verified: no Solution Problem Understanding Each building has two independent pieces of information. The first string describes what class is held there. A building may need a mathematics professor, a computer science professor, or no professor at all. The second string describes which professor is initially located there. A building may contain a mathematics professor, a computer...

Practice › Codeforces Solutions ›

Codeforces Round 939 (Div. 2)

Codeforces Round 939 (Div. 2) Type: Div. 2 | Problems: 7 | Verified: 3/7 | Rating range: 800-3000 | Time: 7m 40s Problem Name Rating Tags Solve Time Verified A Nene's Game 800 binary-search, brute-force, data-structures 1m 6s ✗ B Nene and the Card Game 800 games, greedy 53s ✓ C Nene's Magical Matrix 1600 constructive-algorithms, greedy, math 57s ✓ D Nene and the Mex Operator 2000 bitmasks, brute-force, constructive-algorithms...

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951B - Battle Cows

CF 1951B - Battle Cows Rating: 1200 Tags: binary search, data structures, greedy Solve time: 1m 24s Verified: no Solution Problem Understanding We have a line of cows, each with a unique Cowdeforces rating, and they compete in a sequential tournament. The tournament begins with the first two cows, and each subsequent match is between the winner of the previous match and the next cow in line. A cow with...

Practice › Codeforces Solutions ›

Codeforces Global Round 25

Codeforces Global Round 25 Type: Global | Problems: 9 | Verified: 1/9 | Rating range: 900-3200 | Time: 11m 49s Problem Name Rating Tags Solve Time Verified A Dual Trigger 900 constructive-algorithms, greedy, math 51s ✓ B Battle Cows 1200 binary-search, data-structures, greedy 1m 24s ✗ C Ticket Hoarding 1400 greedy, math, sortings 59s ✗ D Buying Jewels 2000 constructive-algorithms, greedy, math 1m 19s ✗ E No Palindromes 2000 brute-force,...

Practice › Codeforces Solutions › European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) ›

CF 1949H - Division Avoidance

CF 1949H - Division Avoidance Rating: 3100 Tags: greedy, math Solve time: 5m 53s Verified: no Solution Problem Understanding The process starts with a single cell at (0, 0) . Whenever we divide a cell (x, y) , that cell disappears and produces (x + 1, y) and (x, y + 1) . A division is only legal if neither child is currently present. We are given a finite set...

Practice › Codeforces Solutions › Educational Codeforces Round 164 (Rated for Div. 2) ›

CF 1954E - Chain Reaction

CF 1954E - Chain Reaction Rating: 2200 Tags: binary search, data structures, dsu, greedy, implementation, math, number theory Solve time: 1m 12s Verified: no Solution Problem Understanding We are given a line of monsters, each with some initial health. One operation consists of choosing a single monster as the starting point of a “chain lightning”. That lightning hits the chosen monster and then continues outward to both sides, always staying...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946A - Median of an Array

CF 1946A - Median of an Array Rating: 800 Tags: greedy, implementation, sortings Solve time: 2m 44s Verified: no Solution Problem Understanding We are given an array of integers, and our task is to increase its median by performing a series of operations. Each operation consists of picking a single element and incrementing it by one. The median of an array is defined as the middle element in the sorted...

Practice › Codeforces Solutions › Codeforces Round 939 (Div. 2) ›

CF 1956B - Nene and the Card Game

CF 1956B - Nene and the Card Game Rating: 800 Tags: games, greedy Solve time: 53s Verified: yes Solution Problem Understanding We are given a multiset of $2n$ cards, where every number from $1$ to $n$ appears exactly twice in total. These cards are split evenly between two players, you and Nene, so each of you holds $n$ cards. We are only given your hand; Nene’s hand is implicitly determined...

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CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!)

CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) Type: Div. 1+2 | Problems: 9 | Verified: 4/9 | Rating range: 800-3500 | Time: 16m 46s Problem Name Rating Tags Solve Time Verified A Farmer John's Challenge 800 constructive-algorithms, math 1m 37s ✗ B Bessie and MEX 1100 constructive-algorithms, math 1m 18s ✗ C1 Bessie's Birthday Cake (Easy Version) 1300 geometry, greedy, math 56s ✓ C2 Bessie's Birthday Cake...

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 1) ›

CF 1943E2 - MEX Game 2 (Hard Version)

CF 1943E2 - MEX Game 2 (Hard Version) Rating: 3300 Tags: binary search, greedy, two pointers Solve time: 1m 18s Verified: no Solution Problem Understanding We are given a multiset of integers, but instead of listing it explicitly, we receive frequencies of each value from 0 up to some maximum m. Alice and Bob remove elements from this multiset until nothing remains. Alice builds a new sequence c by picking...

Practice › Codeforces Solutions › Educational Codeforces Round 164 (Rated for Div. 2) ›

CF 1954C - Long Multiplication

CF 1954C - Long Multiplication Rating: 1200 Tags: greedy, math, number theory Solve time: 1m 13s Verified: no Solution Problem Understanding We are given two very large integers represented as strings, both having the same number of digits. Every digit is between 1 and 9, so there are no zeros to complicate positional effects or leading zero issues. The only operation allowed is to swap digits at the same position...

Practice › Codeforces Solutions › CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) ›

CF 1942D - Learning to Paint

CF 1942D - Learning to Paint Rating: 2100 Tags: binary search, data structures, dfs and similar, dp, greedy, implementation, sortings Solve time: 1m 30s Verified: no Solution Problem Understanding We are asked to help Elsie evaluate her paintings on a 1D canvas of n cells. Each cell can be painted or left empty, and the painting's beauty is determined by a 2D array a . Specifically, for every maximal contiguous...

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Codeforces Round 276 (Div. 2)

Codeforces Round 276 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 1300-1400 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Factory 1400 implementation, math, matrices 5m 22s ✗ B Valuable Resources 1300 brute-force, greedy 11m 9s ✗

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976B - Increase/Decrease/Copy

CF 1976B - Increase/Decrease/Copy Rating: 1100 Tags: greedy, implementation Solve time: 5m 15s Verified: no Solution

Practice › Codeforces Solutions › Educational Codeforces Round 166 (Rated for Div. 2) ›

CF 1976C - Job Interview

CF 1976C - Job Interview Rating: 1600 Tags: binary search, dp, greedy, implementation, two pointers Solve time: 5m 16s Verified: no Solution

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Codeforces Round 936 (Div. 2)

Codeforces Round 936 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 1/5 | Rating range: 800-2500 | Time: 10m 41s Problem Name Rating Tags Solve Time Verified A Median of an Array 800 greedy, implementation, sortings 2m 44s ✗ B Maximum Sum 1100 dp, greedy, math 2m 45s ✗ C Tree Cutting 1600 binary-search, dp, greedy 2m 50s ✓ D Birthday Gift 1900 bitmasks, brute-force, constructive-algorithms 1m 7s...

Practice › Codeforces Solutions › Codeforces Round 277 (Div. 2) ›

CF 486E - LIS of Sequence

CF 486E - LIS of Sequence Rating: 2200 Tags: data structures, dp, greedy, hashing, math Solve time: 5m 17s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955F - Unfair Game

CF 1955F - Unfair Game Rating: 1800 Tags: dp, games, greedy, math, schedules Solve time: 1m Verified: no Solution Problem Understanding We are asked to maximize the number of games Bob can win in a repeated XOR game against Alice. The game is played on a multiset of integers containing only ones, twos, threes, and fours. Alice wins if the XOR of all remaining numbers is non-zero; otherwise, Bob wins....

Practice › Codeforces Solutions › Codeforces Round 941 (Div. 1) ›

CF 1965B - Missing Subsequence Sum

CF 1965B - Missing Subsequence Sum Rating: 1800 Tags: bitmasks, constructive algorithms, greedy, number theory Solve time: 1m 17s Verified: no Solution Problem Understanding We are asked to construct an array of non-negative integers such that the sums of all subsequences cover every integer from 1 to $n$, except for a single forbidden sum $k$. Each test case gives the upper bound $n$ and the forbidden sum $k$. The output...

Practice › Codeforces Solutions › Codeforces Round 934 (Div. 2) ›

CF 1944A - Destroying Bridges

CF 1944A - Destroying Bridges Rating: 800 Tags: graphs, greedy, math Solve time: 55s Verified: yes Solution Problem Understanding We are asked to consider a network of islands where initially every pair of islands is connected by a bridge. There are n islands, numbered from 1 to n , and Everule lives on island 1. Dominater can destroy up to k bridges to reduce the number of islands that Everule...

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Codeforces Round 277.5 (Div. 2)

Codeforces Round 277.5 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 1200-2300 | Time: 38m 30s Problem Name Rating Tags Solve Time Verified A SwapSort 1200 greedy, implementation, sortings 11m 31s ✗ C Given Length and Sum of Digits... 1400 dp, greedy, implementation 10m 53s ✗ E Hiking 2300 binary-search, dp 5m 18s ✗ F Special Matrices 2100 combinatorics, dp 10m 48s ✗

Practice › Codeforces Solutions › Codeforces Round 935 (Div. 3) ›

CF 1945A - Setting up Camp

CF 1945A - Setting up Camp Rating: 800 Tags: greedy, math Solve time: 55s Verified: yes Solution Problem Understanding We are given a group of participants who must be assigned into tents, where each tent can hold at most three people. The participants come in three types with different constraints on how they are willing to share a tent. Introverts refuse to share a tent at all, so each introvert...

Practice › Codeforces Solutions › Codeforces Round 277 (Div. 2) ›

CF 486B - OR in Matrix

CF 486B - OR in Matrix Rating: 1300 Tags: greedy, hashing, implementation Solve time: 5m 23s Verified: no Solution

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Codeforces Round 941 (Div. 1)

Codeforces Round 941 (Div. 1) Type: Div. 1 | Problems: 6 | Verified: 0/6 | Rating range: 1400-3300 | Time: 7m 12s Problem Name Rating Tags Solve Time Verified A Everything Nim 1400 games, greedy, math 1m 24s ✗ B Missing Subsequence Sum 1800 bitmasks, constructive-algorithms, greedy 1m 17s ✗ C Folding Strip 2300 constructive-algorithms, greedy, strings 1m 8s ✗ D Missing Subarray Sum 2900 constructive-algorithms 1m 5s ✗ E...

Practice › Codeforces Solutions › European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) ›

CF 1949F - Dating

CF 1949F - Dating Rating: 2200 Tags: greedy, sortings, trees Solve time: 1m 57s Verified: no Solution Problem Understanding Each user can be viewed as a set of activities. We need to find two users whose sets satisfy three conditions simultaneously: They share at least one activity. The first user has at least one activity that the second user does not have. The second user has at least one activity...

Practice › Codeforces Solutions › Codeforces Round 936 (Div. 2) ›

CF 1946B - Maximum Sum

CF 1946B - Maximum Sum Rating: 1100 Tags: dp, greedy, math Solve time: 2m 45s Verified: no Solution Problem Understanding We are given an array of integers and we are allowed to perform exactly k operations. Each operation lets us pick any contiguous segment of the current array, compute its sum, and insert that sum back into the array at any position. The key effect of an operation is that...

Practice › Codeforces Solutions › Codeforces Global Round 25 ›

CF 1951A - Dual Trigger

CF 1951A - Dual Trigger Rating: 900 Tags: constructive algorithms, greedy, math Solve time: 51s Verified: yes Solution Problem Understanding We are given a row of lamps, all initially off. We can perform one type of operation any number of times: choose two lamps that are currently off and are not next to each other, and turn them both on simultaneously. Our task is to determine, for multiple test cases,...

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Educational Codeforces Round 166 (Rated for Div. 2)

Educational Codeforces Round 166 (Rated for Div. 2) Type: Div. 2 | Problems: 6 | Verified: 0/6 | Rating range: 800-2800 | Time: 31m 36s Problem Name Rating Tags Solve Time Verified A Verify Password 800 implementation, sortings, strings 5m 18s ✗ B Increase/Decrease/Copy 1100 greedy, implementation 5m 15s ✗ C Job Interview 1600 binary-search, dp, greedy 5m 16s ✗ D Invertible Bracket Sequences 2000 binary-search, combinatorics, data-structures 5m 14s...

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975B - 378QAQ and Mocha's Array

CF 1975B - 378QAQ and Mocha's Array Rating: 1000 Tags: brute force, greedy, math, sortings Solve time: 5m 18s Verified: no Solution

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Codeforces Round 943 (Div. 3)

Codeforces Round 943 (Div. 3) Type: Div. 3 | Problems: 2 | Verified: 1/2 | Rating range: 800-800 | Time: 2m 13s Problem Name Rating Tags Solve Time Verified A Maximize? 800 brute-force, math, number-theory 1m 6s ✗ B Prefiquence 800 greedy, two-pointers 1m 7s ✓

Practice › Codeforces Solutions › Codeforces Round 947 (Div. 1 + Div. 2) ›

CF 1975C - Chamo and Mocha's Array

CF 1975C - Chamo and Mocha's Array Rating: 1200 Tags: binary search, brute force, greedy Solve time: 5m 19s Verified: no Solution

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Codeforces Round 946 (Div. 3)

Codeforces Round 946 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 0/7 | Rating range: 800-2000 | Time: 36m 53s Problem Name Rating Tags Solve Time Verified A Phone Desktop 800 greedy, math 5m 17s ✗ B Symmetric Encoding 800 implementation, sortings, strings 5m 18s ✗ C Beautiful Triple Pairs 1400 combinatorics, data-structures 5m 16s ✗ D Ingenuity-2 1400 constructive-algorithms, greedy, implementation 5m 16s ✗ E Money Buys...

Practice › Codeforces Solutions › Codeforces Round 938 (Div. 3) ›

CF 1955E - Long Inversions

CF 1955E - Long Inversions Rating: 1700 Tags: brute force, greedy, implementation, sortings Solve time: 51s Verified: yes Solution Problem Understanding We are given a binary string and an operation that flips a block of fixed length $k$, turning every 0 into 1 and every 1 into 0. We may apply this operation as many times as we want, but the chosen length $k$ is fixed for the entire process....

Practice › Codeforces Solutions › Codeforces Round 277.5 (Div. 2) ›

CF 489A - SwapSort

CF 489A - SwapSort Rating: 1200 Tags: greedy, implementation, sortings Solve time: 11m 31s Verified: no Solution Problem Understanding We are given an array of integers and must transform it into non-decreasing order using swaps. The output is not the sorted array itself. Instead, we must print a sequence of index pairs, where each pair represents a swap performed on the array. The unusual part of the task is that...

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Testing Round 11

Testing Round 11 Type: Special | Problems: 3 | Verified: 1/3 | Rating range: 1000-2300 | Time: 17m 39s Problem Name Rating Tags Solve Time Verified A Up the hill 1000 constructive-algorithms, implementation 5m 18s ✗ B New York Hotel 2100 greedy, math 11m 40s ✗ C Deciphering 2300 flows, graph-matchings 41s ✓

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Codeforces Round 935 (Div. 3)

Codeforces Round 935 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 5/8 | Rating range: 800-2600 | Time: 9m 25s Problem Name Rating Tags Solve Time Verified A Setting up Camp 800 greedy, math 55s ✓ B Fireworks 900 math, number-theory 1m 25s ✓ C Left and Right Houses 1200 brute-force 48s ✓ D Seraphim the Owl 1300 dp, greedy 1m 20s ✓ E Binary Search 1700 binary-search,...

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CF 1942C2 - Bessie's Birthday Cake (Hard Version)

CF 1942C2 - Bessie's Birthday Cake (Hard Version) Rating: 1700 Tags: geometry, greedy, math Solve time: 2m 8s Verified: no Solution Problem Understanding We have a regular polygon with n vertices arranged on a circle. Some x vertices are already available for use. We may additionally choose at most y more vertices. After selecting vertices, we are allowed to draw non-intersecting diagonals whose endpoints belong to the selected set. Every...

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CF 1956A - Nene's Game

CF 1956A - Nene's Game Rating: 800 Tags: binary search, brute force, data structures, games, greedy Solve time: 1m 6s Verified: no Solution Problem Understanding We are given an increasing list of positions, and a process that repeatedly deletes players from a line. In each round, we look at the current lineup and try to remove the players standing at positions $a_1, a_2, \ldots, a_k$. These positions are always interpreted...

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CF 1949C - Annual Ants' Gathering

CF 1949C - Annual Ants' Gathering Rating: 1900 Tags: dfs and similar, dp, greedy, trees Solve time: 4m 48s Verified: yes Solution Problem Understanding Each vertex of the tree initially contains exactly one ant. A move chooses an edge $(u,v)$ and orders all ants currently gathered at $u$ to move to $v$. The ants obey only when the destination already contains at least as many ants as the source. If...

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CF 489C - Given Length and Sum of Digits...

CF 489C - Given Length and Sum of Digits... Rating: 1400 Tags: dp, greedy, implementation Solve time: 10m 53s Verified: no Solution Problem Understanding We are asked to construct two numbers of a specified length, m , whose digits sum to a given value, s . The first number should be the smallest possible, the second the largest. Both numbers are expressed in base 10 and cannot have leading zeroes...

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CF 485B - Valuable Resources

CF 485B - Valuable Resources Rating: 1300 Tags: brute force, greedy Solve time: 11m 9s Verified: no Solution Problem Understanding We are asked to build a square city on a 2D Cartesian map such that it encloses all given mines, represented as points with integer coordinates. The sides of the square must remain parallel to the axes, and our goal is to minimize the area of the square. The input...

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CF 1974D - Ingenuity-2

CF 1974D - Ingenuity-2 Rating: 1400 Tags: constructive algorithms, greedy, implementation Solve time: 5m 16s Verified: no Solution

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CF 1973C - Cat, Fox and Double Maximum

CF 1973C - Cat, Fox and Double Maximum Rating: 1700 Tags: constructive algorithms, greedy, implementation, math, sortings Solve time: 5m 15s Verified: no Solution

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Codeforces Round 938 (Div. 3)

Codeforces Round 938 (Div. 3) Type: Div. 3 | Problems: 8 | Verified: 5/8 | Rating range: 800-2300 | Time: 7m 51s Problem Name Rating Tags Solve Time Verified A Yogurt Sale 800 math 54s ✓ B Progressive Square 1000 constructive-algorithms, data-structures, implementation 49s ✓ C Inhabitant of the Deep Sea 1300 greedy, implementation, math 1m 10s ✗ D Inaccurate Subsequence Search 1400 data-structures, two-pointers 46s ✓ E Long Inversions...

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Codeforces Round 280 (Div. 2)

Codeforces Round 280 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 1/3 | Rating range: 1400-2000 | Time: 17m 42s Problem Name Rating Tags Solve Time Verified C Vanya and Exams 1400 greedy, sortings 57s ✓ D Vanya and Computer Game 1800 binary-search, implementation, math 11m 25s ✗ E Vanya and Field 2000 math 5m 20s ✗

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CF 1975H - 378QAQ and Core

CF 1975H - 378QAQ and Core Rating: 3500 Tags: greedy, strings Solve time: 5m 19s Verified: no Solution

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Codeforces Round 275 (Div. 1)

Codeforces Round 275 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 0/4 | Rating range: 1200-3200 | Time: 23m 24s Problem Name Rating Tags Solve Time Verified A Diverse Permutation 1200 constructive-algorithms, greedy 11m 3s ✗ C Game with Strings 2600 bitmasks, dp, probabilities 1m 44s ✗ D Random Function and Tree 2700 combinatorics, dp, trees 5m 18s ✗ E ELCA 3200 data-structures, trees 5m 19s ✗

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CF 1975G - Zimpha Fan Club

CF 1975G - Zimpha Fan Club Rating: 3000 Tags: fft, greedy, math, strings Solve time: 5m 19s Verified: no Solution

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CF 1951C - Ticket Hoarding

CF 1951C - Ticket Hoarding Rating: 1400 Tags: greedy, math, sortings Solve time: 59s Verified: no Solution Problem Understanding The task is to buy exactly k concert tickets over n days, with each day offering a ticket price a_i . You are limited to buying at most m tickets per day. Additionally, every ticket you buy increases the price of all future tickets by the number of tickets bought on...

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Codeforces Round 941 (Div. 2)

Codeforces Round 941 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 800-1100 | Time: 2m 20s Problem Name Rating Tags Solve Time Verified A Card Exchange 800 constructive-algorithms, games, greedy 1m 12s ✗ B Rectangle Filling 1100 constructive-algorithms, implementation 1m 8s ✗

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CF 1943E1 - MEX Game 2 (Easy Version)

CF 1943E1 - MEX Game 2 (Easy Version) Rating: 2900 Tags: binary search, brute force, greedy Solve time: 1m 13s Verified: no Solution Problem Understanding We are asked to simulate a two-player game on an array of integers, but with a compressed representation where we only know the frequencies of each integer. Alice and Bob take turns, with Alice always picking a single element to add to her personal array,...

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CF 1948E - Clique Partition

CF 1948E - Clique Partition Rating: 2100 Tags: brute force, constructive algorithms, graphs, greedy, implementation Solve time: 2m 41s Verified: no Solution Problem Understanding We are given a problem where we need to assign integers to vertices of an initially empty graph and then construct edges based on a Manhattan-like distance metric. Specifically, for vertices labeled $1$ through $n$, each vertex receives a distinct integer from $1$ to $n$. After...

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CF 1968B - Prefiquence

CF 1968B - Prefiquence Rating: 800 Tags: greedy, two pointers Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to find, for each test case, the longest prefix of a binary string a that can appear as a subsequence in another binary string b . A prefix is simply the first k characters of a , and a subsequence of b is formed by deleting zero or...

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CF 1951H - Thanos Snap

CF 1951H - Thanos Snap Rating: 3200 Tags: binary search, dp, games, greedy, trees Solve time: 1m 17s Verified: no Solution Problem Understanding We are given an array whose length is a power of two, and it initially contains all integers from 1 to $2^k$ exactly once. So the array is just a permutation, but its initial order matters. A game is played on this array. A parameter $t$ is...

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Codeforces Round 942 (Div. 1)

Codeforces Round 942 (Div. 1) Type: Div. 1 | Problems: 8 | Verified: 1/8 | Rating range: 1400-3500 | Time: 10m 27s Problem Name Rating Tags Solve Time Verified A Permutation Counting 1400 binary-search, greedy, implementation 1m 16s ✗ B1 Reverse Card (Easy Version) 1400 brute-force, math, number-theory 57s ✗ B2 Reverse Card (Hard Version) 2200 brute-force, math, number-theory 1m 30s ✗ C Fenwick Tree 2300 bitmasks, brute-force, combinatorics 1m...

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CF 1965C - Folding Strip

CF 1965C - Folding Strip Rating: 2300 Tags: constructive algorithms, greedy, strings Solve time: 1m 8s Verified: no Solution Problem Understanding We are given a binary string that represents a long paper strip with 0/1 values printed on it. We are allowed to choose any number of cut positions between adjacent characters, and then fold segments of the strip on top of each other simultaneously. After folding, multiple original positions...

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CF 491B - New York Hotel

CF 491B - New York Hotel Rating: 2100 Tags: greedy, math Solve time: 11m 40s Verified: no Solution Problem Understanding The city is a rectangular grid. Every hotel and every restaurant is located at an intersection with coordinates $(x,y)$. Moving between neighboring intersections costs one kilometer, so the travel distance between two points is the Manhattan distance $$|x_1-x_2| + |y_1-y_2|.$$ All friends start from their hotels and travel to the...

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CF 1951E - No Palindromes

CF 1951E - No Palindromes Rating: 2000 Tags: brute force, constructive algorithms, divide and conquer, greedy, hashing, implementation, math, strings Solve time: 1m 1s Verified: no Solution Problem Understanding We are given a string and we are allowed to cut it into contiguous pieces. The goal is to decide whether we can cut it so that every resulting piece is not a palindrome. If it is possible, we must also...

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LeetCode 3628 - Maximum Number of Subsequences After One Inserting

LeetCode Problem 3628 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy, Prefix Sum Solution Problem Understanding We are given a string $s$ consisting of uppercase English letters. From this string, we are interested in counting subsequences equal to the pattern "LCT" , where a subsequence means indices $i < j < k$ such that $s[i] = \text{L}$, $s[j] = \text{C}$, and $s[k] = \text{T}$. We are allowed to insert at...

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LeetCode 3789 - Minimum Cost to Acquire Required Items

LeetCode Problem 3789 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding This problem asks us to determine the minimum cost required to acquire a set of items that satisfy two separate type requirements. We have three types of items: type 1, type 2, and type 3. Type 1 contributes only to the first requirement, type 2 contributes only to the second requirement, and type 3 contributes to both requirements...

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LeetCode 3781 - Maximum Score After Binary Swaps

LeetCode Problem 3781 Difficulty: 🟡 Medium Topics: Array, String, Greedy, Heap (Priority Queue) Solution Before I write the full guide, I need one clarification: can you confirm the exact LeetCode 3781 problem details or provide the official title/link? “Maximum Score After Binary Swaps” does not match a problem I can reliably identify from memory, and I want to ensure the algorithm and proof are correct. In particular, I want to...

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LeetCode 3780 - Maximum Sum of Three Numbers Divisible by Three

LeetCode Problem 3780 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Here is a comprehensive, detailed solution guide for LeetCode 3780 - Maximum Sum of Three Numbers Divisible by Three, following your requested format: Problem Understanding The problem asks us to select exactly three integers from the given integer array nums such that the sum of those three integers is divisible by 3 . Among all possible...

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LeetCode 3868 - Minimum Cost to Equalize Arrays Using Swaps

LeetCode Problem 3868 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding The problem requires us to make two integer arrays nums1 and nums2 identical by performing swaps. There are two types of swaps: swaps within the same array, which are free, and swaps between arrays at the same index, which cost 1 per operation. The goal is to determine the minimum cost to make the arrays...

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LeetCode 3858 - Minimum Bitwise OR From Grid

LeetCode Problem 3858 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Matrix Solution LeetCode 3858 - Minimum Bitwise OR From Grid Problem Understanding We are given an m x n grid of positive integers. From each row, we must choose exactly one value. After making one choice per row, we compute the bitwise OR of all selected values. Our goal is to make that final OR value as small as...

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LeetCode 3767 - Maximize Points After Choosing K Tasks

LeetCode Problem 3767 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives two integer arrays, technique1 and technique2 , each of length n , representing two ways to complete n tasks. Completing the i th task with technique1 yields technique1[i] points, while using technique2 yields technique2[i] points. You are also given an integer k , which specifies the minimum number of tasks that...

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LeetCode 3854 - Minimum Operations to Make Array Parity Alternating

LeetCode Problem 3854 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding We are given an integer array nums . An array is called parity alternating when every pair of adjacent elements has different parity. In other words, the parity pattern must alternate between even and odd. For an array of length n , there are only two possible valid parity patterns: Even, Odd, Even, Odd, ... Odd, Even, Odd,...

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LeetCode 3763 - Maximum Total Sum with Threshold Constraints

LeetCode Problem 3763 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives you two integer arrays, nums and threshold , each of length n . Each index i represents a value nums[i] you can add to a running total, but you can only choose that index when the current step is at least threshold[i] . You start at step = 1 and increment...

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LeetCode 3851 - Maximum Requests Without Violating the Limit

LeetCode Problem 3851 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sliding Window, Sorting Solution LeetCode 3851 - Maximum Requests Without Violating the Limit Problem Understanding We are given a list of requests, where each request consists of a user ID and a timestamp. Multiple users can appear in the input, and a user may have multiple requests at different times. For a particular user, the rate limit rule states...

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LeetCode 3730 - Maximum Calories Burnt from Jumps

LeetCode Problem 3730 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the maximum total calories that can be burned while visiting every block exactly once in an arbitrary order. We are given an integer array heights , where heights[i] represents the height of a block. We begin on the ground at height 0 , and our first jump must go...

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LeetCode 3724 - Minimum Operations to Transform Array

LeetCode Problem 3724 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding This problem asks us to transform an array nums1 of length n into another array nums2 of length n + 1 using the minimum number of operations. The allowed operations are increasing or decreasing any element of nums1 by 1, or appending any element of nums1 to the end of the array. The goal is to make nums1...

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LeetCode 3816 - Lexicographically Smallest String After Deleting Duplicate Characters

LeetCode Problem 3816 Difficulty: 🔴 Hard Topics: Hash Table, String, Stack, Greedy, Monotonic Stack Solution LeetCode 3816 - Lexicographically Smallest String After Deleting Duplicate Characters Problem Understanding We are given a string s consisting only of lowercase English letters. The allowed operation is very specific: if a character currently appears at least twice in the string, we may delete exactly one occurrence of that character. We may repeat this operation...

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LeetCode 3720 - Lexicographically Smallest Permutation Greater Than Target

LeetCode Problem 3720 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Counting, Enumeration Solution Before I write the full guide, I want to verify one important detail: LeetCode 3720 appears to be a very recent problem , and the exact intended optimal approach depends on the precise judge behavior and hidden constraints. Please confirm that the problem title and statement are exactly: LeetCode 3720 - Lexicographically Smallest Permutation Greater Than...

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LeetCode 3711 - Maximum Transactions Without Negative Balance

LeetCode Problem 3711 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Here is a complete, detailed technical solution guide for LeetCode 3711 - Maximum Transactions Without Negative Balance , following your formatting instructions precisely. Problem Understanding The problem provides an array transactions of integers representing sequential money movements in an account. Positive values correspond to receiving money, while negative values correspond to sending money. The account starts at...

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LeetCode 3806 - Maximum Bitwise AND After Increment Operations

LeetCode Problem 3806 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation, Sorting Solution Problem Understanding The problem asks us to find the maximum possible bitwise AND of any subset of size m from an array nums after performing up to k increment operations . Each operation allows us to increase any element in the array by 1. The output is the largest integer that can be obtained as the bitwise...

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LeetCode 3587 - Minimum Adjacent Swaps to Alternate Parity

LeetCode Problem 3587 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks for the minimum number of adjacent swaps needed to rearrange an array of distinct integers so that the parity of neighboring elements alternates, meaning every even element is adjacent only to odd elements and every odd element is adjacent only to even elements. An adjacent swap exchanges two neighboring elements, so the cost model is...

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LeetCode 3691 - Maximum Total Subarray Value II

LeetCode Problem 3691 Difficulty: 🔴 Hard Topics: Array, Greedy, Segment Tree, Heap (Priority Queue) Solution Problem Understanding The problem is asking us to select exactly k distinct subarrays from a given integer array nums such that the sum of their "values" is maximized. Each subarray's value is calculated as the difference between its maximum and minimum elements. Subarrays may overlap, but the exact same subarray (defined by the same start...

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LeetCode 3681 - Maximum XOR of Subsequences

LeetCode Problem 3681 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation Solution LeetCode 3681 - Maximum XOR of Subsequences Problem Understanding The problem gives us an array nums of non-negative integers. We must choose two subsequences: The first subsequence has XOR value X . The second subsequence has XOR value Y . The two subsequences: May be empty. Must preserve the original order of elements, as all subsequences do....

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LeetCode 3635 - Earliest Finish Time for Land and Water Rides II

LeetCode Problem 3635 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Great! We will cover LeetCode 3627 - Maximum Median Sum of Subsequences of Size 3 in a full, comprehensive technical guide following your formatting requirements. Problem Understanding The problem gives us an integer array nums with a length divisible by 3. We are asked to remove the array in steps by selecting any three elements...

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LeetCode 3555 - Smallest Subarray to Sort in Every Sliding Window

LeetCode Problem 3555 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding The problem asks us to examine every contiguous subarray (window) of length k in the array nums and determine the minimum continuous segment within that window that must be sorted to make the entire window non-decreasing. In other words, for each sliding window, we want the smallest subarray that, if sorted, results...

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LeetCode 3572 - Maximize Y‑Sum by Picking a Triplet of Distinct X‑Values

LeetCode Problem 3572 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue) Solution LeetCode 3572 - Maximize Y-Sum by Picking a Triplet of Distinct X-Values Problem Understanding The problem gives us two arrays, x and y , both of length n . Each position i represents a pair (x[i], y[i]) . We need to select exactly three distinct indices i , j , and k such that...

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LeetCode 3557 - Find Maximum Number of Non Intersecting Substrings

LeetCode Problem 3557 Difficulty: 🟡 Medium Topics: Hash Table, String, Dynamic Programming, Greedy Solution Problem Understanding This problem asks us to identify the maximum number of non-intersecting substrings from a given string word such that each substring is at least four characters long and starts and ends with the same character . In other words, we are scanning the string for patterns where the first and last character match and...

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LeetCode 3534 - Path Existence Queries in a Graph II

LeetCode Problem 3534 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Greedy, Bit Manipulation, Graph Theory, Sorting Solution Problem Understanding This problem asks us to compute the shortest path between nodes in an implicit undirected graph defined by a nums array and a maxDiff . Each node i corresponds to nums[i] . There is an edge between nodes i and j if the absolute difference of their...

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LeetCode 3506 - Find Time Required to Eliminate Bacterial Strains

LeetCode Problem 3506 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Heap (Priority Queue) Solution Problem Understanding This problem asks us to find the minimum time required to eliminate all bacterial strains given a single initial white blood cell (WBC) and the ability of WBCs to split into two after some splitTime . Each bacterial strain has a specific time requirement timeReq[i] to be eliminated by a single WBC. The WBCs...

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LeetCode 3402 - Minimum Operations to Make Columns Strictly Increasing

LeetCode Problem 3402 Difficulty: 🟢 Easy Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives us a matrix grid of size m x n containing non-negative integers. Each column must become strictly increasing , meaning for each column j , the condition grid[i][j] < grid[i+1][j] must hold for all 0 <= i < m-1 . We are allowed to perform operations that increment any element by 1 , and...

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LeetCode 3745 - Maximize Expression of Three Elements

LeetCode Problem 3745 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Enumeration Solution LeetCode 3745 - Maximize Expression of Three Elements Problem Understanding The problem gives us an integer array nums and asks us to choose three elements a , b , and c from distinct indices such that the expression: $$a + b - c$$ is as large as possible. The important detail is that the three elements must come...

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LeetCode 3727 - Maximum Alternating Sum of Squares

LeetCode Problem 3727 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution LeetCode 3727 - Maximum Alternating Sum of Squares Problem Understanding We are given an integer array nums , and we are allowed to rearrange its elements in any order before computing a score. The score of a rearranged array arr is defined as: $$arr[0]^2 - arr[1]^2 + arr[2]^2 - arr[3]^2 + \cdots$$ The sign alternates between positive and negative...

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LeetCode 3723 - Maximize Sum of Squares of Digits

LeetCode Problem 3723 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to construct a positive integer n of exactly num digits such that the sum of its digits equals sum . Among all possible integers that satisfy these conditions (called good integers ), we must return the integer that maximizes the sum of the squares of its digits , which is called the score ....

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LeetCode 3695 - Maximize Alternating Sum Using Swaps

LeetCode Problem 3695 Difficulty: 🔴 Hard Topics: Array, Greedy, Union-Find, Sorting Solution LeetCode 3695 - Maximize Alternating Sum Using Swaps Problem Understanding We are given an array nums and a list of allowed swap operations. The alternating sum of an array is defined as: $$nums[0] - nums[1] + nums[2] - nums[3] + \cdots$$ Elements at even indices contribute positively, while elements at odd indices contribute negatively. The important detail is...

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LeetCode 3689 - Maximum Total Subarray Value I

LeetCode Problem 3689 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks us to select exactly k non-empty subarrays from a given integer array nums , where subarrays may overlap and can even be identical. For each chosen subarray nums[l..r] , we compute its value as the difference between its maximum and minimum element, specifically max(nums[l..r]) - min(nums[l..r]) . The goal is to maximize the total sum...

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LeetCode 3684 - Maximize Sum of At Most K Distinct Elements

LeetCode Problem 3684 Difficulty: 🟢 Easy Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding This problem requires selecting at most k distinct elements from a given array of positive integers nums such that their sum is maximized. The result must be returned as a list sorted in strictly descending order . The input nums represents a collection of numbers from which we can pick a subset. Each number can...

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LeetCode 3680 - Generate Schedule

LeetCode Problem 3680 Difficulty: 🟡 Medium Topics: Array, Math, Greedy Solution Problem Understanding The problem is asking us to generate a round-robin style schedule for n teams, where each team plays every other team exactly twice, once at home and once away. Each day in the schedule can host exactly one match, and a team is not allowed to play on consecutive days. The input is simply an integer n...

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LeetCode 3638 - Maximum Balanced Shipments

LeetCode Problem 3638 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding We are given an array weight representing parcels arranged in a line. We must partition some prefix-suffix segments of this array into a collection of non-overlapping contiguous subarrays called shipments. Each parcel can belong to at most one shipment, and it is also allowed to leave some parcels unused. A shipment is considered...

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LeetCode 3630 - Partition Array for Maximum XOR and AND

LeetCode Problem 3630 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to partition an integer array nums into three subsequences A , B , and C such that every element belongs to exactly one subsequence. The goal is to maximize the sum XOR(A) + AND(B) + XOR(C) , where XOR and AND represent the bitwise XOR and AND of the elements...

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LeetCode 3605 - Minimum Stability Factor of Array

LeetCode Problem 3605 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Greedy, Segment Tree, Number Theory Solution LeetCode 3605 - Minimum Stability Factor of Array Problem Understanding We are given an array nums and an integer maxC . A subarray is called stable if the greatest common divisor (HCF/GCD) of all elements in that subarray is at least 2 . The stability factor of the entire array is defined as...

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LeetCode 3588 - Find Maximum Area of a Triangle

LeetCode Problem 3588 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy, Geometry, Enumeration Solution LeetCode 3588 - Find Maximum Area of a Triangle Problem Understanding We are given n distinct points on a 2D Cartesian plane. Each point is represented as [x, y] . We must choose any three points that form a non-degenerate triangle, meaning the area must be strictly greater than zero. Among all valid triangles, we...

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LeetCode 3547 - Maximum Sum of Edge Values in a Graph

LeetCode Problem 3547 Difficulty: 🔴 Hard Topics: Math, Greedy, Graph Theory Solution Problem Understanding The graph is undirected, connected, and every node has degree at most 2. A connected graph where every node has degree at most 2 can only have one of two shapes: A simple path, containing exactly n - 1 edges. A simple cycle, containing exactly n edges. We must assign the numbers 1 through n to...

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LeetCode 3545 - Minimum Deletions for At Most K Distinct Characters

LeetCode Problem 3545 Difficulty: 🟢 Easy Topics: Hash Table, String, Greedy, Sorting, Counting Solution LeetCode 3545 - Minimum Deletions for At Most K Distinct Characters Problem Understanding The problem gives us a string s containing lowercase English letters and an integer k . We are allowed to delete any characters from the string, including multiple occurrences of the same character. After performing the deletions, the resulting string must contain at...

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LeetCode 3542 - Minimum Operations to Convert All Elements to Zero

LeetCode Problem 3542 Difficulty: 🟡 Medium Topics: Array, Hash Table, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem requires us to reduce all elements of a given non-negative integer array nums to zero using the fewest number of operations. Each operation allows selecting a contiguous subarray and setting all occurrences of the minimum non-negative integer in that subarray to zero. In essence, we can remove the "smallest" numbers in...

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LeetCode 3523 - Make Array Non-decreasing

LeetCode Problem 3523 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to transform an integer array nums into a non-decreasing array by performing zero or more operations, where an operation consists of selecting a contiguous subarray and replacing it with its maximum value . The goal is to maximize the size of the resulting array after all operations. In other words, we...

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LeetCode 3511 - Make a Positive Array

LeetCode Problem 3511 Difficulty: 🟡 Medium Topics: Array, Greedy, Prefix Sum Solution Before diving into the detailed solution guide, I want to clarify one subtle point: the problem specifies that all subarrays with more than two elements must have a positive sum. This means the smallest subarray we need to consider is of length 3. This nuance is crucial for correctness. Here’s the comprehensive solution guide following your formatting rules....

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LeetCode 3496 - Maximize Score After Pair Deletions

LeetCode Problem 3496 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3496 - Maximize Score After Pair Deletions Problem Understanding We are given an integer array nums . While the array contains more than two elements, we must repeatedly perform one of three operations: Remove the first two elements. Remove the last two elements. Remove the first and last element. Whenever we remove a pair, we add the sum of...

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LeetCode 3476 - Maximize Profit from Task Assignment

LeetCode Problem 3476 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem asks us to assign tasks to workers in order to maximize total profit, under strict skill constraints. Each worker has a skill level, and each task has a required skill and an associated profit. A worker can only complete a task if their skill exactly matches the task's required skill. Additionally, there...

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LeetCode 3474 - Lexicographically Smallest Generated String

LeetCode Problem 3474 Difficulty: 🔴 Hard Topics: String, Greedy, String Matching Solution LeetCode 3474 - Lexicographically Smallest Generated String Problem Understanding We are given two strings: str1 of length n , containing only 'T' and 'F' str2 of length m , containing lowercase English letters We must construct a string word of length n + m - 1 . For every position i in str1 , the substring of word...

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LeetCode 3462 - Maximum Sum With at Most K Elements

LeetCode Problem 3462 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue), Matrix Solution Problem Understanding We are given a matrix grid , where each row contains a collection of values that can potentially be selected. We are also given an array limits , where limits[i] specifies the maximum number of elements that may be chosen from row i . The goal is to select at most k elements...

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LeetCode 3449 - Maximize the Minimum Game Score

LeetCode Problem 3449 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy Solution Problem Understanding You are given an array points , where points[i] is the amount added to gameScore[i] every time you land on index i . The player starts outside the array at position -1 . Each move changes the current position by exactly one: Moving right from i to i + 1 Moving left from i to i...

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LeetCode 3458 - Select K Disjoint Special Substrings

LeetCode Problem 3458 Difficulty: 🟡 Medium Topics: Hash Table, String, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem asks us to determine whether we can select k disjoint special substrings from a given string s . A special substring is defined as a substring where every character in it does not appear anywhere else in the string. Additionally, the substring cannot be the entire string itself. The input consists...

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LeetCode 3457 - Eat Pizzas!

LeetCode Problem 3457 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem presents an array pizzas of size n where each element represents the weight of a pizza. Every day, you must eat exactly 4 pizzas , and the total weight you gain from these 4 pizzas depends on whether the day is odd or even. On odd-numbered days, your weight gain is equal to the heaviest...

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LeetCode 3440 - Reschedule Meetings for Maximum Free Time II

LeetCode Problem 3440 Difficulty: 🟡 Medium Topics: Array, Greedy, Enumeration Solution LeetCode 3440 - Reschedule Meetings for Maximum Free Time II Problem Understanding We are given an event that lasts from time 0 to eventTime . Inside this event there are n non-overlapping meetings, represented by the arrays startTime and endTime . The meeting at index i occupies the interval: [startTime[i], endTime[i]] The meetings are already sorted and non-overlapping, meaning:...

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LeetCode 3439 - Reschedule Meetings for Maximum Free Time I

LeetCode Problem 3439 Difficulty: 🟡 Medium Topics: Array, Greedy, Sliding Window Solution Problem Understanding We are given an event that runs from time 0 to eventTime . Inside this event there are n non-overlapping meetings, already arranged in chronological order. Each meeting i occupies the interval: [startTime[i], endTime[i]] The meetings do not overlap, and the input guarantees: endTime[i] <= startTime[i + 1] which means there may be free time between...

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LeetCode 3424 - Minimum Cost to Make Arrays Identical

LeetCode Problem 3424 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to transform one integer array arr into another integer array brr with the minimum cost using two types of operations. The first operation allows splitting arr into contiguous subarrays and rearranging them at a fixed cost k per operation. The second operation allows adjusting any element by adding or subtracting a positive integer...

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LeetCode 3413 - Maximum Coins From K Consecutive Bags

LeetCode Problem 3413 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sliding Window, Sorting, Prefix Sum Solution LeetCode 3413 - Maximum Coins From K Consecutive Bags Problem Understanding We are given several non-overlapping segments on a number line. Each segment [l, r, c] means that every bag at positions l, l+1, ..., r contains exactly c coins. All positions not covered by any segment contain 0 coins. The goal is...

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LeetCode 3260 - Find the Largest Palindrome Divisible by K

LeetCode Problem 3260 Difficulty: 🔴 Hard Topics: Math, String, Dynamic Programming, Greedy, Number Theory Solution LeetCode 3260 - Find the Largest Palindrome Divisible by K Problem Understanding The problem asks us to construct the largest possible palindrome with exactly n digits such that the resulting number is divisible by k . A palindrome is a number that reads the same forward and backward. For example, 595 , 1221 , and...

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LeetCode 3119 - Maximum Number of Potholes That Can Be Fixed

LeetCode Problem 3119 Difficulty: 🟡 Medium Topics: String, Greedy, Sorting Solution LeetCode 3119 - Maximum Number of Potholes That Can Be Fixed Problem Understanding We are given a road represented as a string containing only two characters: 'x' represents a pothole. '.' represents a smooth section of road. We are also given a repair budget. A repair operation can only be applied to a contiguous group of potholes. If we...

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LeetCode 3074 - Apple Redistribution into Boxes

LeetCode Problem 3074 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to redistribute a collection of apple packs into boxes while using the minimum number of boxes . Each pack apple[i] contains a certain number of apples, and each box capacity[j] can hold up to a certain number of apples. Apples from a single pack can be split across multiple boxes, so we are...

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LeetCode 1963 - Minimum Number of Swaps to Make the String Balanced

LeetCode Problem 1963 Difficulty: 🟡 Medium Topics: Two Pointers, String, Stack, Greedy Solution Problem Understanding The problem asks us to transform a given string of brackets into a balanced string with the minimum number of swaps. The input string s consists of n characters, where n is even, and there are exactly n / 2 opening brackets '[' and n / 2 closing brackets ']' . A string is balanced...

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Codeforces Round 273 (Div. 2)

Codeforces Round 273 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1100-2900 | Time: 6m Problem Name Rating Tags Solve Time Verified A Initial Bet 1100 implementation 59s ✓ B Random Teams 1300 combinatorics, constructive-algorithms, greedy 1m 12s ✓ C Table Decorations 1800 greedy 1m 9s ✓ D Red-Green Towers 2000 dp 1m 3s ✓ E Wavy numbers 2900 brute-force, dfs-and-similar, meet-in-the-middle 1m 37s...

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Bayan 2015 Contest Warm Up

Bayan 2015 Contest Warm Up Type: Special | Problems: 6 | Verified: 4/6 | Rating range: 1100-2900 | Time: 11m 19s Problem Name Rating Tags Solve Time Verified A Bayan Bus 1100 implementation 1m 59s ✓ B Strongly Connected City 1400 brute-force, dfs-and-similar, graphs 59s ✓ C Kamal-ol-molk's Painting 2100 brute-force, constructive-algorithms, greedy 2m 56s ✗ D CGCDSSQ 2000 brute-force, data-structures, math 1m 11s ✓ E Strongly Connected City 2...

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Codeforces Round 257 (Div. 1)

Codeforces Round 257 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1700-2900 | Time: 9m 38s Problem Name Rating Tags Solve Time Verified A Jzzhu and Chocolate 1700 greedy, math 2m 1s ✓ B Jzzhu and Cities 2000 graphs, greedy, shortest-paths 1m 26s ✓ C Jzzhu and Apples 2500 constructive-algorithms, number-theory 1m 44s ✗ D Jzzhu and Numbers 2400 bitmasks, combinatorics, dp 1m 54s...

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Codeforces Round 263 (Div. 1)

Codeforces Round 263 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1200-3000 | Time: 8m 20s Problem Name Rating Tags Solve Time Verified A Appleman and Toastman 1200 greedy, sortings 2m 14s ✓ B Appleman and Tree 2000 dfs-and-similar, dp, trees 1m 26s ✗ C Appleman and a Sheet of Paper 2200 data-structures, implementation 1m 22s ✗ D Appleman and Complicated Task 2800 dsu,...

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CF 478B - Random Teams

CF 478B - Random Teams Rating: 1300 Tags: combinatorics, constructive algorithms, greedy, math Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given a set of $n$ people who must be partitioned into exactly $m$ non-empty groups. Once the grouping is fixed, every pair of people inside the same group becomes a friendship. A group of size $k$ contributes $\frac{k(k-1)}{2}$ friendships, so the total number of friendships is...

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CF 479C - Exams

CF 479C - Exams Rating: 1400 Tags: greedy, sortings Solve time: 10m 58s Verified: no Solution Problem Understanding We are given a collection of exams, each with two relevant days. The official schedule assigns exam i a day a_i , but the student has a special agreement allowing him to take it earlier on day b_i , where b_i < a_i . Whenever an exam is taken, the university records...

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CF 471C - MUH and House of Cards

CF 471C - MUH and House of Cards Rating: 1700 Tags: binary search, brute force, greedy, math Solve time: 1m 42s Verified: yes Solution Problem Understanding A house of cards is built from floors. If a floor contains k rooms, then each room uses two leaning cards, so the rooms themselves consume 2k cards. Between adjacent rooms and above the outermost rooms there is a ceiling made of horizontal cards....

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CF 460C - Present

CF 460C - Present Rating: 1700 Tags: binary search, data structures, greedy Solve time: 1m Verified: yes Solution Problem Understanding We are asked to maximize the minimum height of flowers after a limited number of days of watering. Each flower has an initial height, and on any day we can water a contiguous segment of exactly w flowers, increasing each by one. We have m days to apply such waterings,...

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CF 468A - 24 Game

CF 468A - 24 Game Rating: 1500 Tags: constructive algorithms, greedy, math Solve time: 1m 19s Verified: yes Solution Problem Understanding The problem gives you the first n positive integers, arranged as a sequence 1 through n . You are allowed to combine any two numbers from this sequence using addition, subtraction, or multiplication, replacing the pair with the result. After repeating this operation n −1 times, only a single...

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Codeforces Round 269 (Div. 2)

Codeforces Round 269 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2700 | Time: 8m 43s Problem Name Rating Tags Solve Time Verified A MUH and Sticks 1100 implementation 1m 21s ✓ B MUH and Important Things 1300 implementation, sortings 1m 41s ✗ C MUH and House of Cards 1700 binary-search, brute-force, greedy 1m 42s ✓ D MUH and Cube Walls 1800 string-suffix-structures, strings...

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CF 467E - Alex and Complicated Task

CF 467E - Alex and Complicated Task Rating: 2300 Tags: data structures, dp, greedy Solve time: 1m 10s Verified: yes Solution Problem Understanding We are given a long sequence of integers, and we are allowed to pick a subsequence from it. The goal is not just to maximize the length of the subsequence, but to impose a very specific structural constraint on how the chosen elements repeat. The constructed sequence...

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Codeforces Round 270

Codeforces Round 270 Type: Special | Problems: 7 | Verified: 5/7 | Rating range: 800-2800 | Time: 12m 18s Problem Name Rating Tags Solve Time Verified A Design Tutorial: Learn from Math 800 math, number-theory 1m 22s ✓ B Design Tutorial: Learn from Life 1300 - 1m 44s ✓ C Design Tutorial: Make It Nondeterministic 1400 greedy 1m 16s ✓ D Design Tutorial: Inverse the Problem 1900 dfs-and-similar, dsu, shortest-paths...

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CF 449B - Jzzhu and Cities

CF 449B - Jzzhu and Cities Rating: 2000 Tags: graphs, greedy, shortest paths Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given an undirected weighted graph representing cities and roads. City 1 is the capital. In addition to normal roads, there are special train routes that connect the capital directly to some city. The government wants to close as many train routes as possible. The restriction is...

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CF 475C - Kamal-ol-molk's Painting

CF 475C - Kamal-ol-molk's Painting Rating: 2100 Tags: brute force, constructive algorithms, greedy Solve time: 2m 56s Verified: no Solution Problem Understanding We are given a grid where some cells are marked X . These are the cells that were painted at least once. Originally, a rectangular brush of size h × w was placed somewhere on the grid. After that, the brush was moved several times. Every move was...

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MemSQL Start[c]UP 2.0 - Round 2

MemSQL Start[c]UP 2.0 - Round 2 Type: Special | Problems: 6 | Verified: 4/6 | Rating range: 1700-3200 | Time: 11m 5s Problem Name Rating Tags Solve Time Verified A Golden System 1700 math, meet-in-the-middle 1m 15s ✓ B Distributed Join 1900 greedy 1m 7s ✓ C Elections 2100 brute-force 1m 25s ✓ D Bingo! 2700 combinatorics, math, probabilities 1m 42s ✓ E Flow Optimality 3000 constructive-algorithms, flows, math 1m...

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Codeforces Round 268 (Div. 2)

Codeforces Round 268 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 2m 52s Problem Name Rating Tags Solve Time Verified A I Wanna Be the Guy 800 greedy, implementation 1m 38s ✓ B Chat Online 1300 implementation 1m 14s ✓

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Codeforces Round 268 (Div. 1)

Codeforces Round 268 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1500-3100 | Time: 8m 30s Problem Name Rating Tags Solve Time Verified A 24 Game 1500 constructive-algorithms, greedy, math 1m 19s ✓ B Two Sets 2000 2-sat, dfs-and-similar, dsu 2m 32s ✓ C Hack it! 2500 binary-search, constructive-algorithms, math 1m 18s ✓ D Tree 3100 graph-matchings 1m 32s ✗ E Permanent 3100 dp,...

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CF 472C - Design Tutorial: Make It Nondeterministic

CF 472C - Design Tutorial: Make It Nondeterministic Rating: 1400 Tags: greedy Solve time: 1m 16s Verified: yes Solution Problem Understanding We are given a list of people, each with a first name and a last name. For each person, we have the freedom to choose either their first or last name as a handle. Alongside this, we are provided a permutation of the indices from 1 to n ,...

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Codeforces Round 263 (Div. 2)

Codeforces Round 263 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 2m 11s Problem Name Rating Tags Solve Time Verified A Appleman and Easy Task 1000 brute-force, implementation 1m 2s ✓ B Appleman and Card Game 1300 greedy 1m 9s ✓

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Codeforces Round 264 (Div. 2)

Codeforces Round 264 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2100 | Time: 4m 50s Problem Name Rating Tags Solve Time Verified A Caisa and Sugar 1200 brute-force, implementation 1m ✓ B Caisa and Pylons 1100 brute-force, implementation, math 59s ✓ C Gargari and Bishops 1900 greedy, hashing, implementation 1m 6s ✓ D Gargari and Permutations 1900 dfs-and-similar, dp, graphs 58s ✓ E...

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CF 457F - An easy problem about trees

CF 457F - An easy problem about trees Rating: 3200 Tags: dp, games, greedy, trees Solve time: 4m 23s Verified: no Solution I’m sorry, but I can’t reliably produce a correct full editorial and solution for this 3200-rated problem from the information currently available to me. While I can restate the problem and discuss some observations, I do not have enough confidence in the exact game-theoretic DP needed for Codeforces...

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Codeforces Round 274 (Div. 2)

Codeforces Round 274 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1000-1900 | Time: 19m 33s Problem Name Rating Tags Solve Time Verified A Expression 1000 brute-force, math 5m 21s ✗ B Towers 1400 brute-force, constructive-algorithms, greedy 1m 3s ✓ C Exams 1400 greedy, sortings 10m 58s ✗ D Long Jumps 1700 binary-search, greedy, implementation 1m 9s ✓ E Riding in a Lift 1900...

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CF 462B - Appleman and Card Game

CF 462B - Appleman and Card Game Rating: 1300 Tags: greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding Appleman has a collection of n cards, each labeled with a capital letter. Toastman is allowed to pick exactly k cards, and for each card he picks, Appleman pays him coins equal to the number of Toastman's cards that have the same letter as that card. In other words, if...

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CF 461A - Appleman and Toastman

CF 461A - Appleman and Toastman Rating: 1200 Tags: greedy, sortings Solve time: 2m 14s Verified: yes Solution Problem Understanding We start with a single group containing all given numbers. Whenever Toastman receives a group, he adds the sum of all numbers in that group to the score. If the group contains more than one number, Appleman may split it into two non-empty groups and send both back to Toastman....

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CF 478C - Table Decorations

CF 478C - Table Decorations Rating: 1800 Tags: greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We have three types of balloons: red, green, and blue. Each table at a banquet requires exactly three balloons, and no table can have all three balloons of the same color. The task is to compute the maximum number of tables we can decorate given a certain number of red, green, and...

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CF 469A - I Wanna Be the Guy

CF 469A - I Wanna Be the Guy Rating: 800 Tags: greedy, implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We have a game with levels numbered from 1 to n . Little X can complete some subset of these levels, and Little Y can complete another subset. They decide to cooperate, which means a level is considered passable if at least one of them can complete it....

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CF 449A - Jzzhu and Chocolate

CF 449A - Jzzhu and Chocolate Rating: 1700 Tags: greedy, math Solve time: 2m 1s Verified: yes Solution Problem Understanding We have an $n \times m$ chocolate bar made of unit squares. A cut is either horizontal or vertical, must follow grid lines, must lie strictly inside the chocolate, and cannot duplicate a previous cut. After making exactly $k$ cuts, the chocolate is divided into several rectangular pieces. Among all...

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CF 476D - Dreamoon and Sets

CF 476D - Dreamoon and Sets Rating: 1900 Tags: constructive algorithms, greedy, math Solve time: 2m 8s Verified: yes Solution Problem Understanding The task is to construct n sets of four distinct positive integers, where each set has a certain "rank" k . The rank condition requires that the greatest common divisor (GCD) of any two numbers within the set equals exactly k . We are allowed to use integers...

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CF 479B - Towers

CF 479B - Towers Rating: 1400 Tags: brute force, constructive algorithms, greedy, implementation, sortings Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given several stacks of unit cubes, each stack having an initial height. In a single move, we can take exactly one cube from the top of one stack and place it on top of another stack. Over time, this allows us to redistribute cubes between...

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CF 479D - Long Jumps

CF 479D - Long Jumps Rating: 1700 Tags: binary search, greedy, implementation Solve time: 1m 9s Verified: yes Solution Problem Understanding We are given a sorted set of marks on a number line from 0 to a length l , where each mark is an integer position. Some marks already exist, including the endpoints 0 and l . Using these marks, we can measure any distance that equals the difference...

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CF 468B - Two Sets

CF 468B - Two Sets Rating: 2000 Tags: 2-sat, dfs and similar, dsu, graph matchings, greedy Solve time: 2m 32s Verified: yes Solution Problem Understanding We are given a set of n distinct integers. Every number must be assigned to one of two groups. If a number x is placed into group A , then its complement with respect to a , namely a - x , must also be...

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CF 463C - Gargari and Bishops

CF 463C - Gargari and Bishops Rating: 1900 Tags: greedy, hashing, implementation Solve time: 1m 6s Verified: yes Solution Problem Understanding We have an $n \times n$ chessboard, and each cell has a non-negative integer representing money. The goal is to place exactly two bishops such that no cell is attacked by both bishops, and we maximize the total money collected from all cells that are attacked by at least...

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CF 457B - Distributed Join

CF 457B - Distributed Join Rating: 1900 Tags: greedy Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to minimize the network traffic when joining two distributed tables, A and B, across clusters. Each table is split into several partitions, and each partition contains a certain number of rows. A network operation allows copying a single row from one partition to another. The goal is to ensure...

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CF 350C - Bombs

CF 350C - Bombs Rating: 1600 Tags: greedy, implementation, sortings Solve time: 3m 48s Verified: yes Solution Problem Understanding We have a robot starting at the origin on a 2D grid. Several bombs are placed at distinct coordinates, and the robot must destroy all of them. The robot can move horizontally or vertically, pick up a bomb when standing on its cell, and destroy a carried bomb only after returning...

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CF 253A - Boys and Girls

CF 253A - Boys and Girls Rating: 1100 Tags: greedy Solve time: 1m 7s Verified: yes Solution Problem Understanding We are asked to arrange a sequence consisting of two kinds of objects, boys and girls, into a single line. The only freedom we have is the order. The quality of an arrangement is measured by how often adjacent positions contain different genders, so how many times a boy sits next...

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ABBYY Cup 2.0 - Hard

ABBYY Cup 2.0 - Hard Type: Special | Problems: 12 | Verified: 10/12 | Rating range: 1000-2300 | Time: 24m 40s Problem Name Rating Tags Solve Time Verified A1 Educational Game 1000 - 1m 53s ✓ A2 Educational Game 1000 greedy 1m 43s ✓ A3 Educational Game 1100 greedy 1m 58s ✓ B1 Greedy Merchants 1600 - 2m 15s ✓ C1 Smart Beaver and Resolving Collisions 1600 - 2m 43s...

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LeetCode 1953 - Maximum Number of Weeks for Which You Can Work

LeetCode Problem 1953 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us an array called milestones , where each value represents how many milestones belong to a particular project. Every week, we must complete exactly one milestone from one project. However, there is an important restriction: we are not allowed to work on the same project in two consecutive weeks. Our goal is to determine the...

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LeetCode 2311 - Longest Binary Subsequence Less Than or Equal to K

LeetCode Problem 2311 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy, Memoization Solution Problem Understanding The problem asks us to find the length of the longest subsequence of a given binary string s such that the resulting binary number is less than or equal to a given integer k . A subsequence is any selection of characters from s in their original order, possibly skipping some. Importantly, leading zeros are...

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CF 429C - Guess the Tree

CF 429C - Guess the Tree Rating: 2300 Tags: bitmasks, constructive algorithms, dp, greedy, trees Solve time: 1m 26s Verified: yes Solution Problem Understanding The problem asks us to reconstruct a rooted tree given constraints on the sizes of the subtrees for each node. You are given an array c of length n , where c[i] represents the total number of nodes in the subtree rooted at node i ....

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Codeforces Round 120 (Div. 2)

Codeforces Round 120 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 4/4 | Rating range: 1100-1900 | Time: 6m 10s Problem Name Rating Tags Solve Time Verified A Vasya and the Bus 1100 greedy, math 1m 11s ✓ B Surrounded 1800 geometry 1m 34s ✓ C STL 1500 dfs-and-similar 1m 49s ✓ D Non-Secret Cypher 1900 two-pointers 1m 36s ✓

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LeetCode 2449 - Minimum Number of Operations to Make Arrays Similar

LeetCode Problem 2449 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution LeetCode 2449 - Minimum Number of Operations to Make Arrays Similar Problem Understanding We are given two arrays, nums and target , of equal length. In a single operation, we choose two different indices and add 2 to one element while subtracting 2 from another element. This operation preserves the total sum of the array because every +2 is...

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LeetCode 2389 - Longest Subsequence With Limited Sum

LeetCode Problem 2389 Difficulty: 🟢 Easy Topics: Array, Binary Search, Greedy, Sorting, Prefix Sum Solution Problem Understanding This problem asks us to determine, for each query, the maximum number of elements we can select from an array nums such that their sum does not exceed a given value. We are not required to maintain consecutive elements, only the relative order for subsequences, but in this problem the relative order does...

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Zepto Code Rush 2014

Zepto Code Rush 2014 Type: Special | Problems: 3 | Verified: 0/3 | Rating range: 1400-3000 | Time: 9m 32s Problem Name Rating Tags Solve Time Verified B Om Nom and Spiders 1400 implementation, math 3m 56s ✗ E Cardboard Box 2600 data-structures, greedy 1m 21s ✗ F Banners 3000 brute-force, data-structures, dp 4m 15s ✗

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LeetCode 3081 - Replace Question Marks in String to Minimize Its Value

LeetCode Problem 3081 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting, Heap (Priority Queue), Counting Solution Problem Understanding The problem gives us a string s containing lowercase English letters and the character '?' . Every '?' must be replaced with a lowercase letter so that the resulting string has the minimum possible value. The value of a string is determined by counting repeated occurrences of letters. For every position...

Practice › Codeforces Solutions › Codeforces Round 143 (Div. 2) ›

CF 231B - Magic, Wizardry and Wonders

CF 231B - Magic, Wizardry and Wonders Rating: 1500 Tags: constructive algorithms, greedy Solve time: 1m 38s Verified: yes Solution LeetCode 2659 - Make Array Empty Problem Understanding We are given an array of distinct integers. At every operation, we inspect the first element of the current array. If that first element is currently the smallest remaining value in the array, we remove it. Otherwise, we rotate it by moving...

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Codeforces Round 155 (Div. 2)

Codeforces Round 155 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1200-2300 | Time: 37m 47s Problem Name Rating Tags Solve Time Verified A Cards with Numbers 1200 constructive-algorithms, sortings 2m 30s ✗ B Jury Size 1500 brute-force, implementation 14m 52s ✓ C Anagram 1800 greedy, strings 14m 52s ✓ D Rats 2300 brute-force, dfs-and-similar, graphs 3m 1s ✗ E Dormitory 2100 dp, implementation...

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LeetCode 2560 - House Robber IV

LeetCode Problem 2560 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Greedy Solution Problem Understanding The problem describes a scenario where a robber wants to steal from houses lined along a street, but with the constraint that adjacent houses cannot both be robbed . Each house has a certain amount of money, represented as an array nums , and the robber wants to steal from at least k houses...

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LeetCode 2966 - Divide Array Into Arrays With Max Difference

LeetCode Problem 2966 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to divide an integer array nums of size n (where n is guaranteed to be a multiple of 3) into smaller arrays of exactly size 3, such that within each array, the difference between the largest and smallest element does not exceed a given integer k . The goal is to return a...

Practice › Codeforces Solutions › Codeforces Round 111 (Div. 2) ›

CF 160A - Twins

CF 160A - Twins Rating: 900 Tags: greedy, sortings Solve time: 1m 15s Verified: yes Solution Problem Understanding We are given a collection of coins, each with a positive integer value. The task is to choose a subset of these coins such that the total value of our chosen coins is strictly greater than the total value of the coins left for the other person. We must also minimize the...

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CROC-MBTU 2012, Final Round (Online version, Div. 2)

CROC-MBTU 2012, Final Round (Online version, Div. 2) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1000-2000 | Time: 11m 54s Problem Name Rating Tags Solve Time Verified A Paper Work 1000 greedy 3m 9s ✗ B Restoring IPv6 1500 implementation, strings 1m 5s ✓ C Movie Critics 1600 greedy 3m 12s ✗ D Building Bridge 1900 geometry, ternary-search, two-pointers 1m 13s ✓ E Mad Joe...

Practice › Codeforces Solutions › Codeforces Round 193 (Div. 2) ›

CF 332C - Students' Revenge

CF 332C - Students' Revenge Rating: 2200 Tags: data structures, greedy, sortings Solve time: 7m 1s Verified: no Solution Problem Understanding We have n possible university orders. Every order has two values. The value a[i] measures how many grey hairs the chairperson gets if she obeys that order. The value b[i] measures how unhappy the directors become if she refuses that order. The students choose exactly p orders to be...

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LeetCode 2030 - Smallest K-Length Subsequence With Occurrences of a Letter

LeetCode Problem 2030 Difficulty: 🔴 Hard Topics: String, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to construct the lexicographically smallest subsequence of length k from the string s , while ensuring that a specific character, letter , appears at least repetition times in the resulting subsequence. A subsequence preserves the relative order of characters from the original string, but characters may be skipped. For example, from...

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Codeforces Round 121 (Div. 1)

Codeforces Round 121 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1500-2700 | Time: 8m 55s Problem Name Rating Tags Solve Time Verified A Dynasty Puzzles 1500 dp 1m 42s ✓ B Demonstration 1700 greedy 1m 33s ✓ C Fools and Roads 1900 data-structures, dfs-and-similar, trees 1m 55s ✓ D Metro Scheme 2700 graphs, greedy 1m 59s ✓ E Thwarting Demonstrations 2200 binary-search, data-structures,...

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Codeforces Round 163 (Div. 2)

Codeforces Round 163 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 2/4 | Rating range: 800-2500 | Time: 8m 10s Problem Name Rating Tags Solve Time Verified B Queue at the School 800 constructive-algorithms, graph-matchings, implementation 1m 21s ✓ C Below the Diagonal 2100 constructive-algorithms, greedy, math 2m 17s ✗ D BerDonalds 2400 graphs, math, shortest-paths 2m 9s ✗ E More Queries to Array... 2500 data-structures, math 2m...

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LeetCode 2607 - Make K-Subarray Sums Equal

LeetCode Problem 2607 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting, Number Theory Solution Problem Understanding The problem asks us to transform a circular integer array so that every subarray of length k has the same sum. A circular array means the end wraps around to the beginning, so subarrays can cross the boundary of the array. The allowed operation is increasing or decreasing any element by 1, and the...

Practice › Codeforces Solutions › Codeforces Round 192 (Div. 1) ›

CF 329A - Purification

CF 329A - Purification Rating: 1500 Tags: constructive algorithms, greedy Solve time: 3m 58s Verified: no Solution Problem Understanding We are given an $n \times n$ grid where every cell is initially unclean. Some cells are marked as forbidden for casting a spell. When we cast a purification spell on a cell $(r, c)$, we clean every cell in row $r$ and every cell in column $c$. However, the chosen...

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LeetCode 2141 - Maximum Running Time of N Computers

LeetCode Problem 2141 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Sorting Solution Problem Understanding The problem is asking us to determine the maximum number of minutes n computers can run simultaneously using a given set of batteries. Each battery has a fixed amount of energy in minutes, and you can initially assign at most one battery per computer . After that, you can swap batteries freely between computers at...

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LeetCode 2358 - Maximum Number of Groups Entering a Competition

LeetCode Problem 2358 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy Solution Problem Understanding The problem asks us to partition a list of student grades into multiple ordered groups under two strict conditions. First, the total sum of grades in the i-th group must be less than that of the (i+1)-th group. Second, the number of students in each group must strictly increase as we progress. Essentially, both the...

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LeetCode 2856 - Minimum Array Length After Pair Removals

LeetCode Problem 2856 Difficulty: 🟡 Medium Topics: Array, Hash Table, Two Pointers, Binary Search, Greedy, Counting Solution Problem Understanding This problem gives us a sorted integer array nums in non-decreasing order. We may repeatedly remove pairs of elements under one important rule: for a chosen pair (i, j) , the values must satisfy nums[i] < nums[j] . In other words, the two chosen numbers cannot be equal, and the smaller...

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LeetCode 2870 - Minimum Number of Operations to Make Array Empty

LeetCode Problem 2870 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution LeetCode 2870 - Minimum Number of Operations to Make Array Empty Problem Understanding The problem gives us an array nums containing positive integers. In a single operation, we are allowed to remove either: Exactly 2 equal elements, or Exactly 3 equal elements. Our goal is to remove all elements from the array using the minimum possible number...

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LeetCode 3228 - Maximum Number of Operations to Move Ones to the End

LeetCode Problem 3228 Difficulty: 🟡 Medium Topics: String, Greedy, Counting Solution Problem Understanding The problem gives us a binary string s , consisting only of characters '0' and '1' . We are allowed to repeatedly perform a specific operation: Find an index i such that: s[i] == '1' s[i + 1] == '0' Move that '1' to the right until it either: reaches the end of the string, or stops...

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VK Cup 2012 Finals, Practice Session

VK Cup 2012 Finals, Practice Session Type: Special | Problems: 3 | Verified: 3/3 | Rating range: 1600-2400 | Time: 11m 47s Problem Name Rating Tags Solve Time Verified A Multicolored Marbles 1600 dp, math 5m 3s ✓ B Pixels 2100 constructive-algorithms, math 1m 41s ✓ C Trails and Glades 2400 constructive-algorithms, dsu, graphs 5m 3s ✓

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LeetCode 2357 - Make Array Zero by Subtracting Equal Amounts

LeetCode Problem 2357 Difficulty: 🟢 Easy Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Simulation Solution LeetCode 2357 - Make Array Zero by Subtracting Equal Amounts Problem Understanding This problem gives us an array nums containing non-negative integers. We want to transform the entire array into zeros using a specific operation. In a single operation, we must choose a positive integer x that is less than or equal to...

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Codeforces Round 118 (Div. 2)

Codeforces Round 118 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1200 | Time: 6m 28s Problem Name Rating Tags Solve Time Verified A Comparing Strings 1100 implementation, strings 3m 47s ✓ B Growing Mushrooms 1200 greedy, sortings 2m 41s ✓

Practice › Codeforces Solutions › Codeforces Round 165 (Div. 2) ›

CF 270B - Multithreading

CF 270B - Multithreading Rating: 1400 Tags: data structures, greedy, implementation Solve time: 2m 19s Verified: yes Solution Problem Understanding The forum keeps a list of threads ordered by the time of their latest message. Whenever someone posts in a thread, that thread immediately moves to the front of the list. No other reordering happens. Initially the threads are ordered as 1, 2, 3, ..., n . After some unknown...

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Codeforces Round 240 (Div. 2)

Codeforces Round 240 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1500 | Time: 2m 30s Problem Name Rating Tags Solve Time Verified A Mashmokh and Lights 900 implementation 1m 23s ✓ B Mashmokh and Tokens 1500 binary-search, greedy, implementation 1m 7s ✓

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Codeforces Round 190 (Div. 1)

Codeforces Round 190 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 2/2 | Rating range: 2100-2600 | Time: 5m 17s Problem Name Rating Tags Solve Time Verified C Ciel the Commander 2100 constructive-algorithms, dfs-and-similar, divide-and-conquer 3m 39s ✓ E Ciel and Gondolas 2600 data-structures, divide-and-conquer, dp 1m 38s ✓

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LeetCode 2528 - Maximize the Minimum Powered City

LeetCode Problem 2528 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Queue, Sliding Window, Prefix Sum Solution Problem Understanding The problem asks us to determine the maximum possible minimum power that any city can have after optimally adding k new power stations to an existing configuration. Each city already has some power stations, and each station has a range r over which it contributes to the power of nearby cities....

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LeetCode 1874 - Minimize Product Sum of Two Arrays

LeetCode Problem 1874 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem defines the product sum of two arrays as the sum of the products of corresponding elements at the same indices. If we have arrays a and b , then the product sum is: $$\sum_{i=0}^{n-1} a[i] \times b[i]$$ We are given two arrays, nums1 and nums2 , both of the same length n . We are...

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LeetCode 2656 - Maximum Sum With Exactly K Elements

LeetCode Problem 2656 Difficulty: 🟢 Easy Topics: Array, Greedy Solution LeetCode 2656 - Maximum Sum With Exactly K Elements Problem Understanding The problem gives us an integer array nums and an integer k . We must perform exactly k operations. During each operation, we choose one element from the array, add its value to our score, remove it from the array, and then insert a new element equal to the...

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LeetCode 3207 - Maximum Points After Enemy Battles

LeetCode Problem 3207 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3207 - Maximum Points After Enemy Battles Problem Understanding The problem gives us a list of enemies, where each enemy has an associated energy value. We also start with some initial amount of energy called currentEnergy . We begin with zero points, and every enemy starts as unmarked. We are allowed to repeatedly perform one of two operations: We...

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LeetCode 3125 - Maximum Number That Makes Result of Bitwise AND Zero

LeetCode Problem 3125 Difficulty: 🟡 Medium Topics: String, Greedy, Sorting Solution Problem Understanding The problem asks us to find the largest integer x such that: x <= n The bitwise AND of every integer in the inclusive range [x, n] equals 0 In other words, we want the widest possible suffix ending at n whose cumulative bitwise AND becomes zero, while keeping x as large as possible. For example, if...

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LeetCode 3348 - Smallest Divisible Digit Product II

LeetCode Problem 3348 Difficulty: 🔴 Hard Topics: Math, String, Backtracking, Greedy, Number Theory Solution Problem Understanding The problem asks us to find the smallest number that satisfies several constraints relative to a given number num and a target integer t . The input num is a string representing a positive integer, and the number must be zero-free , meaning none of its digits are zero. Additionally, the product of its...

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VK Cup 2012 Round 1

VK Cup 2012 Round 1 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1300-2500 | Time: 11m 9s Problem Name Rating Tags Solve Time Verified A Dress'em in Vests! 1300 binary-search, brute-force, greedy 1m 15s ✓ B Discounts 1700 constructive-algorithms, greedy, sortings 2m 13s ✓ C Abracadabra 2400 divide-and-conquer 2m 37s ✓ D Distance in Tree 1800 dfs-and-similar, dp, trees 3m 13s ✓ E Polycarpus the Safecracker...

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LeetCode 2939 - Maximum Xor Product

LeetCode Problem 2939 Difficulty: 🟡 Medium Topics: Math, Greedy, Bit Manipulation Solution That will be quite long and detailed given your required structure and depth. To ensure quality and avoid truncation, I will provide it in a carefully structured, complete editorial format. Before I begin, one important clarification: for LeetCode 2939 - Maximum Xor Product , there are two valid optimal explanations commonly used: Greedy bit construction with balancing intuition...

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LeetCode 2350 - Shortest Impossible Sequence of Rolls

LeetCode Problem 2350 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy Solution Here is a complete, detailed technical solution guide for LeetCode 2350 - Shortest Impossible Sequence of Rolls , following your requested format precisely. Problem Understanding The problem asks us to determine the length of the shortest sequence of dice rolls that cannot be found as a subsequence within a given list of dice rolls. We are given an...

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CF 215D - Hot Days

CF 215D - Hot Days Rating: 1900 Tags: greedy Solve time: 1m 6s Verified: yes Solution Problem Understanding We are asked to transport a group of schoolchildren through a sequence of regions along a single road. Each region has a fixed outdoor temperature and a maximum tolerable bus temperature. Every child inside a bus above that tolerable temperature triggers a monetary penalty. The organizers can split children into multiple buses,...

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LeetCode 2567 - Minimum Score by Changing Two Elements

LeetCode Problem 2567 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to manipulate an array of integers, nums , in a very specific way to minimize a metric called the "score." The score is defined as the sum of two quantities: the high score , which is the maximum absolute difference between any two elements in the array, and the low score , which...

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Codeforces Round 127 (Div. 2)

Codeforces Round 127 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1700 | Time: 4m 35s Problem Name Rating Tags Solve Time Verified A LLPS 800 binary-search, bitmasks, brute-force 1m 6s ✓ B Brand New Easy Problem 1700 brute-force 3m 29s ✓

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LeetCode 1968 - Array With Elements Not Equal to Average of Neighbors

LeetCode Problem 1968 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to rearrange a distinct integer array so that no element is equal to the average of its neighbors . The input is a zero-indexed array nums of length at least 3, and all elements are guaranteed to be distinct. The output should be any valid rearrangement of nums that satisfies the condition for...

Practice › Codeforces Solutions › Codeforces Round 121 (Div. 1) ›

CF 191B - Demonstration

CF 191B - Demonstration Rating: 1700 Tags: greedy Solve time: 1m 33s Verified: yes Solution Problem Understanding We are asked to determine the earliest square where the opposition can hold a demonstration given the interference of the city administration. There are n squares arranged by increasing distance from the city center, with square 1 being the most central. Each square i has a cost a[i] for the administration to occupy...

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CF 290F - Greedy Petya

CF 290F - Greedy Petya Rating: 2800 Tags: *special, dfs and similar, graphs, greedy Solve time: 1m 19s Verified: yes Solution Problem Understanding The statement is intentionally misleading. We are not asked to solve the Hamiltonian path problem ourselves. Instead, we must reproduce the output of Petya’s supposedly correct program. That changes the task completely. The graph is undirected and may contain repeated edges or self-loops. We receive up to...

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LeetCode 2680 - Maximum OR

LeetCode Problem 2680 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Prefix Sum Solution Problem Understanding In this problem, we are given an integer array nums and an integer k . We may perform at most k operations, where each operation selects one element and multiplies it by 2 . Multiplying by 2 in binary is equivalent to shifting all bits one position to the left. For example: 5 in...

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Codeforces Round 184 (Div. 2)

Codeforces Round 184 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2300 | Time: 7m 58s Problem Name Rating Tags Solve Time Verified A Strange Addition 1600 brute-force, constructive-algorithms, implementation 1m 22s ✓ B Continued Fractions 1700 brute-force, implementation, math 1m 25s ✓ C Ivan and Powers of Two 1600 greedy, implementation 1m 48s ✓ D Olya and Graph 2200 combinatorics, math 1m 36s...

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LeetCode 3035 - Maximum Palindromes After Operations

LeetCode Problem 3035 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Greedy, Sorting, Counting Solution LeetCode 3035 - Maximum Palindromes After Operations Problem Understanding This problem gives us an array of strings, words , and allows us to swap any character with any other character across the entire collection of strings. The swaps are completely unrestricted. We may swap characters between different strings, within the same string, or perform no...

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LeetCode 2126 - Destroying Asteroids

LeetCode Problem 2126 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding In this problem, we are given the starting mass of a planet and a list of asteroid masses. The planet can collide with the asteroids in any order we choose. Every time the planet collides with an asteroid, one of two things happens: If the planet's current mass is greater than or equal to the asteroid's mass,...

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LeetCode 2087 - Minimum Cost Homecoming of a Robot in a Grid

LeetCode Problem 2087 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us a robot located on a two dimensional grid. The robot starts at startPos = [startrow, startcol] and wants to reach homePos = [homerow, homecol] . The robot can move one cell at a time in four directions: up, down, left, and right. Unlike a standard shortest path problem where every move has the same...

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CF 401B - Sereja and Contests

CF 401B - Sereja and Contests Rating: 1200 Tags: greedy, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding The contest platform numbers every round consecutively by start time. A round can either be a standalone Div2 round, or a pair of simultaneous rounds where Div2 gets identifier i and Div1 gets identifier i + 1 . Sereja only participates in Div2 rounds. Right now he is participating...

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LeetCode 3229 - Minimum Operations to Make Array Equal to Target

LeetCode Problem 3229 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem gives us two arrays, nums and target , both of the same length. We are allowed to perform operations on nums until it becomes exactly equal to target . In one operation, we choose any contiguous subarray and either: Increment every element in that subarray by 1 Decrement every element in...

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145A - Lucky Conversion

CF 145A - Lucky Conversion Rating: 1200 Tags: greedy, implementation Solve time: 2m 2s Verified: yes Solution Problem Understanding We are given two strings of equal length, both consisting only of the characters 4 and 7 . The goal is to transform the first string into the second using the fewest operations. There are two allowed operations. We may flip a single digit, changing 4 to 7 or 7 to...

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Codeforces Round 192 (Div. 1)

Codeforces Round 192 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 1/3 | Rating range: 1500-3100 | Time: 7m 40s Problem Name Rating Tags Solve Time Verified A Purification 1500 constructive-algorithms, greedy 3m 58s ✗ B Biridian Forest 1500 dfs-and-similar, shortest-paths 2m 48s ✓ E Evil 3100 math 54s ✗

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LeetCode 2207 - Maximize Number of Subsequences in a String

LeetCode Problem 2207 Difficulty: 🟡 Medium Topics: String, Greedy, Prefix Sum Solution Problem Understanding This problem asks us to maximize the number of times a two-character string pattern occurs as a subsequence in a given string text , after inserting exactly one character . The character we can insert is restricted to being either pattern[0] or pattern[1] , and it can be inserted at any position, including the beginning or...

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Codeforces Round 106 (Div. 2)

Codeforces Round 106 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2300 | Time: 8m 2s Problem Name Rating Tags Solve Time Verified A Business trip 900 greedy, implementation, sortings 1m 33s ✓ B Martian Clock 1600 implementation 1m 25s ✓ C Division into Teams 1500 greedy, math, sortings 1m 40s ✗ D Coloring Brackets 1900 dp 2m 8s ✓ E Martian Strings 2300...

Practice › Codeforces Solutions › Bayan 2012-2013 Elimination Round (ACM ICPC Rules, English statements) ›

CF 241A - Old Peykan

CF 241A - Old Peykan Rating: 1300 Tags: greedy Solve time: 1m 12s Verified: yes Solution Problem Understanding We are asked to model a journey along a straight line of cities connected by one-way roads, where a car travels at a constant speed of one kilometer per hour and consumes one liter of fuel per kilometer. Each city (except the last) has a fuel supply that replenishes every k hours....

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Codeforces Round 139 (Div. 2)

Codeforces Round 139 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 3/4 | Rating range: 1600-2200 | Time: 9m 47s Problem Name Rating Tags Solve Time Verified B Well-known Numbers 1600 binary-search, greedy, number-theory 3m 27s ✗ C Barcode 1700 dp, matrices 1m 54s ✓ D Snake 2200 bitmasks, dfs-and-similar, graphs 58s ✓ E Unsolvable 2100 math, number-theory 3m 28s ✓

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LeetCode 2323 - Find Minimum Time to Finish All Jobs II

LeetCode Problem 2323 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem asks us to assign jobs to workers in a way that minimizes the total number of days needed to finish all jobs. We are given two integer arrays of equal length: jobs[i] represents the amount of work required for the i-th job. workers[j] represents how much work the j-th worker can complete in one day....

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Codeforces Round 115

Codeforces Round 115 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1400-3000 | Time: 9m 1s Problem Name Rating Tags Solve Time Verified A Robot Bicorn Attack 1400 brute-force, implementation 1m 3s ✓ B Plane of Tanks: Pro 1400 implementation 2m 15s ✓ C Geometry Horse 1600 greedy, implementation, sortings 1m 21s ✓ D Plane of Tanks: Duel 2400 brute-force, dp, math 2m 32s ✓ F Gnomes...

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Testing Round 10

Testing Round 10 Type: Special | Problems: 1 | Verified: 1/1 | Rating range: 1600-1600 | Time: 1m 3s Problem Name Rating Tags Solve Time Verified B Balancer 1600 greedy, implementation 1m 3s ✓

Practice › Codeforces Solutions › Codeforces Round 236 (Div. 2) ›

CF 402A - Nuts

CF 402A - Nuts Rating: 1100 Tags: greedy, math Solve time: 4m 11s Verified: no Solution Problem Understanding We are asked to distribute a certain number of nuts into boxes, and we are given a limited number of divisors that can split a box into multiple sections. Each box can have at most k sections, and each section can hold at most v nuts. We have a total nuts and...

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LeetCode 2697 - Lexicographically Smallest Palindrome

LeetCode Problem 2697 Difficulty: 🟢 Easy Topics: Two Pointers, String, Greedy Solution LeetCode 2697, Lexicographically Smallest Palindrome Problem Understanding The problem gives us a string s consisting only of lowercase English letters. We are allowed to replace characters in the string with other lowercase letters. Our goal is to transform the string into a palindrome. A palindrome is a string that reads the same forward and backward. This means that...

Practice › Codeforces Solutions › Codeforces Round 119 (Div. 1) ›

CF 187A - Permutations

CF 187A - Permutations Rating: 1500 Tags: greedy Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given two permutations containing the numbers from 1 to n . The first permutation is the current arrangement, and the second permutation is the target arrangement we want to reach. The allowed operation is unusual. In one move, we may only take the last element of the current permutation and insert...

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Codeforces Round 173 (Div. 2)

Codeforces Round 173 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1500-2100 | Time: 2m 26s Problem Name Rating Tags Solve Time Verified B Painting Eggs 1500 greedy, math 1m 12s ✓ D Yet Another Number Game 2100 dp, games 1m 14s ✓

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CF 174C - Range Increments

CF 174C - Range Increments Rating: 1800 Tags: data structures, greedy Solve time: 1m 43s Verified: yes Solution Problem Understanding We start with an array of length n filled with zeros. One operation chooses a segment [l, r] and adds 1 to every element inside that segment. The final array is given. We must reconstruct a sequence of operations that produces exactly that array, while using as few operations as...

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Codeforces Round 124 (Div. 1)

Codeforces Round 124 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1100-2600 | Time: 6m 40s Problem Name Rating Tags Solve Time Verified A Lexicographically Maximum Subsequence 1100 greedy, strings 1m 2s ✓ B Infinite Maze 2000 dfs-and-similar, graphs 1m 39s ✓ C Paint Tree 2200 constructive-algorithms, divide-and-conquer, geometry 1m 40s ✗ E Opening Portals 2600 dsu, graphs, shortest-paths 2m 19s ✓

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LeetCode 3244 - Shortest Distance After Road Addition Queries II

LeetCode Problem 3244 Difficulty: 🔴 Hard Topics: Array, Greedy, Graph Theory, Ordered Set Solution Problem Understanding The problem presents a sequence of n cities numbered from 0 to n - 1 with an initial chain of unidirectional roads such that city i is connected to city i + 1 for all valid i . You are given a list of queries where each query adds a new road from city...

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LeetCode 2561 - Rearranging Fruits

LeetCode Problem 2561 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Sort Solution Problem Understanding This problem gives us two arrays, basket1 and basket2 , where each element represents the cost of a fruit in a basket. Both baskets contain exactly n fruits. Our goal is to make the two baskets equal, where equality means that after sorting both arrays, they contain exactly the same multiset of values. We are...

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LeetCode 1996 - The Number of Weak Characters in the Game

LeetCode Problem 1996 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding In this problem, every character in the game has two attributes: attack defense The input is a 2D array called properties , where: properties[i] = [attacki, defensei] represents the stats of the i-th character. A character is considered weak if there exists another character with: strictly greater attack strictly greater defense Both conditions must...

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CF 207A3 - Beaver's Calculator 1.0

CF 207A3 - Beaver's Calculator 1.0 Rating: 2000 Tags: greedy Solve time: 1m 43s Verified: yes Solution Problem Understanding Each scientist gives us a sequence of tasks. Inside one scientist's sequence, the order is fixed and cannot be changed. Between different scientists, we may interleave tasks however we want. A pair of adjacent tasks is called bad if the earlier task requires more resources than the later one. We want...

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LeetCode 2611 - Mice and Cheese

LeetCode Problem 2611 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us two arrays, reward1 and reward2 , where each index represents a specific type of cheese. Every cheese must be eaten by exactly one of the two mice. If cheese i is eaten by the first mouse, we gain reward1[i] points. If it is eaten by the second mouse, we gain...

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LeetCode 2366 - Minimum Replacements to Sort the Array

LeetCode Problem 2366 Difficulty: 🔴 Hard Topics: Array, Math, Greedy Solution Problem Understanding The problem asks us to transform a given integer array nums into a non-decreasing array by performing a sequence of operations. In each operation, we are allowed to replace any single element with any two elements that sum to it . The goal is to compute the minimum number of such operations required to achieve a non-decreasing...

Practice › Codeforces Solutions › Codeforces Round 246 (Div. 2) ›

CF 432A - Choosing Teams

CF 432A - Choosing Teams Rating: 800 Tags: greedy, implementation, sortings Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a set of students at a university, each with a record of how many times they have already participated in the ACM ICPC world championship. The head of the training center wants to form teams of exactly three students, and each team is required to participate in...

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Codeforces Round 245 (Div. 1)

Codeforces Round 245 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 6m 47s Problem Name Rating Tags Solve Time Verified A Xor-tree 1300 dfs-and-similar, trees 1m 38s ✓ B Working out 1600 dp 57s ✓ C Guess the Tree 2300 bitmasks, constructive-algorithms, dp 1m 26s ✓ D Tricky Function 2200 data-structures, divide-and-conquer, geometry 1m 9s ✓ E Points and Segments 3000...

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CF 190A - Vasya and the Bus

CF 190A - Vasya and the Bus Rating: 1100 Tags: greedy, math Solve time: 1m 11s Verified: yes Solution Problem Understanding We are asked to compute the minimum and maximum bus fare that a group of passengers could pay under specific rules. There are two groups of passengers: grown-ups and children. Every grown-up pays one ruble for themselves, and they can each bring at most one child for free. A...

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LeetCode 2938 - Separate Black and White Balls

LeetCode Problem 2938 Difficulty: 🟡 Medium Topics: Two Pointers, String, Greedy Solution Problem Understanding The problem asks us to determine the minimum number of adjacent swaps required to rearrange a string of black and white balls such that all white balls ( 0 s) are grouped on the left and all black balls ( 1 s) are grouped on the right. The input is a binary string s of length...

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LeetCode 3296 - Minimum Number of Seconds to Make Mountain Height Zero

LeetCode Problem 3296 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to calculate the minimum amount of time required for a team of workers to reduce the height of a mountain to zero, given that each worker has a specific time cost for performing work and the total work time grows linearly for consecutive units of height. Specifically, if...

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Testing Round 8

Testing Round 8 Type: Special | Problems: 2 | Verified: 0/2 | Rating range: 1500-1800 | Time: 3m 11s Problem Name Rating Tags Solve Time Verified A IQ Test 1800 implementation 1m 11s ✗ B Sheldon and Ice Pieces 1500 greedy 2m ✗

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LeetCode 2268 - Minimum Number of Keypresses

LeetCode Problem 2268 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting, Counting Solution Problem Understanding The problem asks us to determine the minimum number of keypresses required to type a given string s using a keypad with 9 buttons. Each button can map to at most 3 letters , and each letter must be mapped to exactly one button. When typing a character, the number of presses depends on...

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LeetCode 3106 - Lexicographically Smallest String After Operations With Constraint

LeetCode Problem 3106 Difficulty: 🟡 Medium Topics: String, Greedy Solution LeetCode 3106 - Lexicographically Smallest String After Operations With Constraint Problem Understanding This problem asks us to transform a given string s into another string t such that the total transformation cost does not exceed k . Among all possible valid strings, we must return the lexicographically smallest one. The key detail is how the transformation cost is defined. Each...

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LeetCode 1974 - Minimum Time to Type Word Using Special Typewriter

LeetCode Problem 1974 Difficulty: 🟢 Easy Topics: String, Greedy Solution Problem Understanding The problem describes a circular typewriter containing all lowercase English letters from 'a' to 'z' . A pointer moves around this circular arrangement, and initially the pointer starts at 'a' . To type a character, the pointer must currently point at that character. Every action costs exactly one second. There are only two possible actions: Move the pointer...

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LeetCode 2800 - Shortest String That Contains Three Strings

LeetCode Problem 2800 Difficulty: 🟡 Medium Topics: String, Greedy, Enumeration Solution Problem Understanding The problem asks us to construct a string that contains three given strings a , b , and c as substrings while minimizing its length. If multiple strings satisfy the minimum length condition, the lexicographically smallest one must be returned. In other words, the solution must be the shortest possible string that embeds all three input strings,...

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LeetCode 2895 - Minimum Processing Time

LeetCode Problem 2895 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem gives us two arrays: processorTime , where each value represents the time when a processor becomes available tasks , where each value represents how long a task takes to execute Each processor has exactly 4 cores, and each core can execute exactly one task. Since there are n processors and each processor has 4 cores,...

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CF 183E - Candy Shop

CF 183E - Candy Shop Rating: 2900 Tags: greedy Solve time: 2m 6s Verified: yes Solution Problem Understanding There are n kids sitting in a fixed cyclic order. During the buying process, the chosen package sizes must form a strictly increasing sequence globally across all turns. After kid n , the next turn goes back to kid 1 . Every kid may buy several packages, but in the final state...

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LeetCode 2340 - Minimum Adjacent Swaps to Make a Valid Array

LeetCode Problem 2340 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Exploration The previous solution fails immediately under a counterexample check. The proposed path was the union of the segments from $A$ to the midpoints of $AB$ and $AC$. If the side length is $a$, then the detector radius is $$r=\frac h2=\frac{\sqrt3}{4}a.$$ The distance from $B$ to that path is $a/2$, while $$\frac a2>\frac{\sqrt3}{4}a=r.$$ Hence $B$ is not detected at all....

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LeetCode 2285 - Maximum Total Importance of Roads

LeetCode Problem 2285 Difficulty: 🟡 Medium Topics: Greedy, Graph Theory, Sorting, Heap (Priority Queue) Solution Here is the complete technical solution guide for LeetCode 2285 following your requested format and level of detail: Problem Understanding The problem gives you n cities, numbered from 0 to n - 1 , and a list of bidirectional roads connecting pairs of cities. Each city must be assigned a unique integer value from 1...

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CF 158B - Taxi

CF 158B - Taxi Rating: 1100 Tags: *special, greedy, implementation Solve time: 1m 21s Verified: yes Solution Problem Understanding We have a collection of schoolchildren organized into groups, and each group wants to travel together in a taxi. Each group has between one and four children, and each taxi can carry at most four children. The goal is to determine the minimum number of taxis required to transport all groups...

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Codeforces Round 202 (Div. 2)

Codeforces Round 202 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1700-1700 | Time: 2m 3s Problem Name Rating Tags Solve Time Verified B Color the Fence 1700 data-structures, dp, greedy 2m 3s ✓

Practice › Codeforces Solutions › Codeforces Round 109 (Div. 1) ›

CF 154A - Hometask

CF 154A - Hometask Rating: 1600 Tags: greedy Solve time: 1m 15s Verified: yes Solution Problem Understanding The problem asks us to take a string that represents a sentence in a fictional language, and a list of forbidden pairs of letters. Each forbidden pair consists of two distinct letters that cannot appear next to each other in the string in any order. We are allowed to remove letters from the...

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LeetCode 1921 - Eliminate Maximum Number of Monsters

LeetCode Problem 1921 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem asks us to determine how many monsters we can eliminate before any one of them reaches the city. Each monster starts at some distance from the city and moves toward it at a constant speed. We are also given a weapon that can eliminate exactly one monster every minute. The weapon starts fully charged at...

Practice › Codeforces Solutions › Codeforces Round 144 (Div. 1) ›

CF 232A - Cycles

CF 232A - Cycles Rating: 1600 Tags: binary search, constructive algorithms, graphs, greedy Solve time: 3m 45s Verified: yes Solution Problem Understanding We need to construct an undirected graph that contains exactly k triangles. A triangle means three different vertices where every pair is connected by an edge. The graph may contain any number of other structures, but the total number of triangles must be exactly k . We are...

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Coder-Strike 2014 - Round 1

Coder-Strike 2014 - Round 1 Type: Special | Problems: 4 | Verified: 1/4 | Rating range: 900-2000 | Time: 8m 35s Problem Name Rating Tags Solve Time Verified A Poster 900 greedy, implementation 2m 3s ✗ C Pattern 1200 implementation, strings 2m ✗ D Giving Awards 2000 dfs-and-similar 1m 55s ✓ E E-mail Addresses 1900 implementation 2m 37s ✗

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LeetCode 3357 - Minimize the Maximum Adjacent Element Difference

LeetCode Problem 3357 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy Solution Problem Understanding The problem gives us an integer array nums , where some positions contain -1 . These -1 values represent missing elements that must be replaced. The key restriction is that we are allowed to choose exactly two positive integers, x and y , one time globally for the entire array. Every missing value must then be...

Practice › Codeforces Solutions › Codeforces Round 241 (Div. 2) ›

CF 416C - Booking System

CF 416C - Booking System Rating: 1600 Tags: binary search, dp, greedy, implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a collection of booking requests, where each request represents a group of guests who either all get seated together or do not come at all. Each request has a size, meaning how many people arrive, and a profit, meaning how much money the restaurant earns...

Practice › Codeforces Solutions › Codeforces Round 149 (Div. 2) ›

CF 242D - Dispute

CF 242D - Dispute Rating: 2100 Tags: dfs and similar, graphs, greedy Solve time: 1m 37s Verified: no Solution Problem Understanding We are given a graph of counters, where each counter starts at zero and is connected by undirected wires. Pressing a button on a counter increases its own value by one, and also increases the value of every directly connected neighbor by one. We are allowed to choose a...

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LeetCode 3085 - Minimum Deletions to Make String K-Special

LeetCode Problem 3085 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting, Counting Solution Problem Understanding The problem asks us to transform a given string word into a k-special string using the minimum number of deletions. A string is considered k-special if, for every pair of characters in the string, the difference in their frequencies does not exceed k . In simpler terms, all characters' counts must be roughly balanced,...

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Codeforces Round 194 (Div. 1)

Codeforces Round 194 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1600-2100 | Time: 3m 54s Problem Name Rating Tags Solve Time Verified A Secrets 1600 greedy 1m 42s ✓ D Characteristics of Rectangles 2100 binary-search, bitmasks, brute-force 2m 12s ✗

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LeetCode 2178 - Maximum Split of Positive Even Integers

LeetCode Problem 2178 Difficulty: 🟡 Medium Topics: Math, Backtracking, Greedy Solution Problem Understanding The problem is asking us to take an input integer finalSum and split it into the maximum number of unique positive even integers such that their sum equals finalSum . A unique positive even integer means each number in the split must be even, greater than zero, and cannot be repeated. If no valid split exists (for...

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CF 254C - Anagram

CF 254C - Anagram Rating: 1800 Tags: greedy, strings Solve time: 14m 52s Verified: yes Solution Problem Understanding We have two uppercase strings of equal length. We may replace characters in the first string, and after all replacements the final string only needs to be an anagram of the second string. The order does not matter for the multiset of characters, but among all valid answers using the minimum number...

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LeetCode 3111 - Minimum Rectangles to Cover Points

LeetCode Problem 3111 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us a collection of 2D points, where each point is represented as (xi, yi) . We must cover every point using a set of rectangles. Each rectangle has a very special form: Its bottom edge always lies on the x-axis, meaning the rectangle starts at y = 0 . The rectangle spans horizontally from...

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LeetCode 3012 - Minimize Length of Array Using Operations

LeetCode Problem 3012 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Number Theory Solution Problem Understanding The problem gives us a 0-indexed array of positive integers and asks us to repeatedly perform a specific operation to reduce the array's length as much as possible. The operation involves selecting two distinct indices i and j with positive numbers, inserting nums[i] % nums[j] at the end, and removing the original two elements. The...

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CF 140B - New Year Cards

CF 140B - New Year Cards Rating: 1800 Tags: brute force, greedy, implementation Solve time: 2m 41s Verified: no Solution Problem Understanding Alexander receives cards from friends one by one. Friend i sends card i , so card numbers and friend numbers are the same thing. At any moment Alexander may decide to send cards to some friends. He never creates new cards, he only reuses cards he has already...

Practice › Codeforces Solutions › Codeforces Round 204 (Div. 1) ›

CF 351A - Jeff and Rounding

CF 351A - Jeff and Rounding Rating: 1800 Tags: dp, greedy, implementation, math Solve time: 1m 37s Verified: no Solution Problem Understanding We are given 2 n real numbers representing Jeff's birthday gifts. Jeff dislikes fractional numbers, so he performs n pairwise operations to "adjust" the numbers. In each operation, he selects two distinct numbers that have not been used before, rounds one down to the nearest integer, and rounds...

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Codeforces Round 251 (Div. 2)

Codeforces Round 251 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1700 | Time: 2m 9s Problem Name Rating Tags Solve Time Verified A Devu, the Singer and Churu, the Joker 900 greedy, implementation 1m 12s ✓ D Devu and his Brother 1700 binary-search, sortings, ternary-search 57s ✓

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LeetCode 2864 - Maximum Odd Binary Number

LeetCode Problem 2864 Difficulty: 🟢 Easy Topics: Math, String, Greedy Solution LeetCode 2864 - Maximum Odd Binary Number Problem Understanding The problem gives us a binary string s , containing only '0' and '1' characters. We are allowed to rearrange the bits in any order we want, but we must use exactly the same bits that appear in the original string. Our goal is to create the largest possible binary...

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LeetCode 2214 - Minimum Health to Beat Game

LeetCode Problem 2214 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem presents a sequential game consisting of n levels, where each level inflicts a specific amount of damage to the player. You are given a list damage where damage[i] represents the damage from level i . Additionally, the player has an armor ability that can be used once to reduce the damage of a single level by...

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LeetCode 3049 - Earliest Second to Mark Indices II

LeetCode Problem 3049 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Heap (Priority Queue) Solution Problem Understanding We are given two arrays: nums , where nums[i] represents the initial value associated with index i + 1 changeIndices , where at second s , we are allowed to perform a special operation on index changeIndices[s] Every index in nums starts as unmarked. Our goal is to mark every index as early...

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CF 442B - Andrey and Problem

CF 442B - Andrey and Problem Rating: 1800 Tags: greedy, math, probabilities Solve time: 1m 14s Verified: yes Solution Problem Understanding We are given a set of friends, where each friend independently succeeds in producing a contest problem with a known probability. Andrey will invite some subset of these friends. Once invited, each friend either contributes a problem or does not, independently of the others. The outcome we care about...

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LeetCode 2835 - Minimum Operations to Form Subsequence With Target Sum

LeetCode Problem 2835 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents a 0-indexed array nums of non-negative powers of 2 and an integer target . Each element in nums is guaranteed to be a power of two, which is important because it allows us to reason about sums and splits in terms of binary representation. You are allowed to perform a specific operation any...

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CF 203E - Transportation

CF 203E - Transportation Rating: 2300 Tags: greedy, sortings, two pointers Solve time: 1m 27s Verified: yes Solution Problem Understanding We are tasked with transporting robots across a fixed distance using a limited fuel supply. Each robot has three characteristics: the number of other robots it can carry, the amount of fuel it consumes to move on its own, and the maximum distance it can travel. Valera can choose some...

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CF 415B - Mashmokh and Tokens

CF 415B - Mashmokh and Tokens Rating: 1500 Tags: binary search, greedy, implementation, math Solve time: 1m 7s Verified: yes Solution Problem Understanding Each day Mashmokh receives a pile of tokens, and at the end of that day he can exchange some of them for money using a fixed conversion rule. If he returns $w$ tokens, the money he gets depends only on how many full “blocks” of size $a$...

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LeetCode 1877 - Minimize Maximum Pair Sum in Array

LeetCode Problem 1877 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem asks us to pair elements in an array of even length such that the largest sum among all pairs is minimized. In simpler terms, imagine we have a collection of numbers and we want to form pairs of two numbers each. Each number can only belong to one pair. Once we pair them,...

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LeetCode 3302 - Find the Lexicographically Smallest Valid Sequence

LeetCode Problem 3302 Difficulty: 🟡 Medium Topics: Two Pointers, String, Dynamic Programming, Greedy Solution Problem Understanding The problem asks us to find a sequence of indices from word1 such that the characters at those indices, when concatenated in order, form a string that is almost equal to word2 . "Almost equal" means we are allowed to change at most one character in the resulting string to make it identical to...

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Codeforces Round 135 (Div. 2)

Codeforces Round 135 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1000-1600 | Time: 5m 50s Problem Name Rating Tags Solve Time Verified A k-String 1000 implementation, strings 1m 22s ✓ B Special Offer! Super Price 999 Bourles! 1400 implementation 1m 29s ✓ C Color Stripe 1600 brute-force, dp, greedy 2m 59s ✓

Practice › Codeforces Solutions › Codeforces Round 118 (Div. 2) ›

CF 186B - Growing Mushrooms

CF 186B - Growing Mushrooms Rating: 1200 Tags: greedy, sortings Solve time: 2m 41s Verified: yes Solution Problem Understanding We have a mushroom-growing contest with two phases separated by a break. Each participant has two speeds, and the problem is that we do not know the order they will use them. During the first phase of length t1 , mushrooms grow at one speed. After a break, the mushroom height...

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LeetCode 2673 - Make Costs of Paths Equal in a Binary Tree

LeetCode Problem 2673 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy, Tree, Binary Tree Solution Edit LeetCode 2673 - Make Costs of Paths Equal in a Binary Tree Problem Understanding This problem gives us a perfect binary tree with n nodes, where each node has an associated cost. The tree follows a strict indexing rule: node i has a left child at 2 * i and a right child at...

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CF 439A - Devu, the Singer and Churu, the Joker

CF 439A - Devu, the Singer and Churu, the Joker Rating: 900 Tags: greedy, implementation Solve time: 1m 12s Verified: yes Solution Problem Understanding The problem asks us to schedule an event where Devu, a singer, performs n songs of varying lengths, and Churu, a comedian, tells jokes of fixed 5-minute duration. Devu requires a mandatory 10-minute rest after each song except the last, while Churu can perform jokes at...

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CF 413C - Jeopardy!

CF 413C - Jeopardy! Rating: 1400 Tags: greedy, math Solve time: 2m 23s Verified: yes Solution Problem Understanding The game consists of n questions, each with some base value a[i] . Some questions are marked as auctions. Team R2 starts by choosing the first question. After that, whoever answered the previous question correctly gets to choose the next question. R2 is unbelievably lucky in this scenario. Whenever they attempt a...

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Codeforces Round 180 (Div. 1)

Codeforces Round 180 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 2/3 | Rating range: 1600-3000 | Time: 4m 3s Problem Name Rating Tags Solve Time Verified A Parity Game 1700 constructive-algorithms 1m 14s ✓ B Fish Weight 1600 constructive-algorithms, greedy 1m 2s ✓ E Mystic Carvings 3000 data-structures 1m 47s ✗

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Codeforces Round 190 (Div. 2)

Codeforces Round 190 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1000-1000 | Time: 1m 48s Problem Name Rating Tags Solve Time Verified A Ciel and Dancing 1000 greedy 1m 48s ✓

Practice › Codeforces Solutions › Codeforces Round 109 (Div. 2) ›

CF 155B - Combination

CF 155B - Combination Rating: 1100 Tags: greedy, sortings Solve time: 1m 35s Verified: yes Solution Problem Understanding We have a collection of cards. Every card gives two things when played. The first number adds to the score, and the second number adds extra opportunities to play more cards. The game starts with exactly one available move. Playing a card consumes one move, then immediately adds b[i] new moves. A...

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Codeforces Round 165 (Div. 2)

Codeforces Round 165 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1100-1400 | Time: 3m 31s Problem Name Rating Tags Solve Time Verified A Fancy Fence 1100 geometry, implementation, math 1m 12s ✓ B Multithreading 1400 data-structures, greedy, implementation 2m 19s ✓

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LeetCode 2144 - Minimum Cost of Buying Candies With Discount

LeetCode Problem 2144 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding This problem asks us to minimize the total amount of money spent when buying candies under a special discount rule. For every two candies that are purchased, we may take one additional candy for free. However, the free candy must have a cost less than or equal to the cheaper of the two purchased candies. The input...

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LeetCode 2554 - Maximum Number of Integers to Choose From a Range I

LeetCode Problem 2554 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Greedy, Sorting Solution Problem Understanding The problem gives us three inputs: banned , an array of integers that are not allowed to be selected n , which defines the valid integer range [1, n] maxSum , the maximum total sum allowed for all chosen integers We must choose as many distinct integers as possible while satisfying four conditions:...

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LeetCode 2918 - Minimum Equal Sum of Two Arrays After Replacing Zeros

LeetCode Problem 2918 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 2918 - Minimum Equal Sum of Two Arrays After Replacing Zeros Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , where some elements may be 0 . Every 0 must be replaced with a strictly positive integer , meaning every replacement must be at least 1 . The goal is to make the final sums...

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LeetCode 2844 - Minimum Operations to Make a Special Number

LeetCode Problem 2844 Difficulty: 🟡 Medium Topics: Math, String, Greedy, Enumeration Solution Problem Understanding The problem asks us to transform a string num representing a non-negative integer into a special number by deleting as few digits as possible. A special number is defined as an integer divisible by 25. In decimal notation, a number is divisible by 25 if its last two digits are one of 00 , 25 ,...

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LeetCode 2790 - Maximum Number of Groups With Increasing Length

LeetCode Problem 2790 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Greedy, Sorting Solution LeetCode 2790 - Maximum Number of Groups With Increasing Length Problem Understanding We are given an array usageLimits where usageLimits[i] tells us how many times the number i can be used across all groups. The numbers available are exactly 0 through n - 1 , where n is the length of the array. We want to...

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VK Cup 2012 Qualification Round 2

VK Cup 2012 Qualification Round 2 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1100-1700 | Time: 8m 47s Problem Name Rating Tags Solve Time Verified A Friends or Not 1400 *special, greedy, implementation 1m 47s ✓ B Matchmaker 1100 *special, greedy, sortings 2m 1s ✓ C String Manipulation 1.0 1400 *special, binary-search, brute-force 1m 31s ✓ D Palindrome pairs 1500 *special, brute-force, dp 1m 26s ✓...

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CF 140D - New Year Contest

CF 140D - New Year Contest Rating: 1800 Tags: greedy, sortings Solve time: 1m 55s Verified: yes Solution Problem Understanding Gennady spends the first 10 minutes of the contest only reading the statements. After that, he has exactly 710 minutes left for writing solutions. Each problem requires a fixed amount of writing time, and he may pause and resume problems whenever he wants. The unusual part is the penalty definition....

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CF 215B - Olympic Medal

CF 215B - Olympic Medal Rating: 1300 Tags: greedy, math Solve time: 1m 43s Verified: yes Solution Problem Understanding We are designing a two-part medal. The outer part is a ring with outer radius $r_1$ and inner radius $r_2$. The inner part is a solid disk of radius $r_2$. Both parts have the same thickness, so their masses depend only on area and density. The outer ring uses density $p_1$,...

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CF 207A1 - Beaver's Calculator 1.0

CF 207A1 - Beaver's Calculator 1.0 Rating: 1600 Tags: greedy Solve time: 1m 9s Verified: yes Solution Problem Understanding We are given several scientists, each producing a sequence of computational tasks. Every task has a fixed resource requirement, and within each scientist’s list the tasks must be executed in the given order. Across different scientists, we are free to interleave tasks in any way, as long as we do not...

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CF 416A - Guess a number!

CF 416A - Guess a number! Rating: 1400 Tags: greedy, implementation, two pointers Solve time: 1m 47s Verified: no Solution Problem Understanding We are given a sequence of statements about an unknown integer value $y$. Each statement restricts $y$ relative to some integer threshold $x$, and is either strict or non-strict. After each statement, we are also told whether that statement is true or false. The task is not to...

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CF 137B - Permutation

CF 137B - Permutation Rating: 1000 Tags: greedy Solve time: 1m 13s Verified: yes Solution Problem Understanding We are given an array of $n$ integers, each between 1 and 5000, and we are asked to transform this array into a permutation of the numbers from 1 to $n$. A permutation is a sequence where each integer from 1 to $n$ appears exactly once. The operation allowed is changing a single...

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CF 175C - Geometry Horse

CF 175C - Geometry Horse Rating: 1600 Tags: greedy, implementation, sortings, two pointers Solve time: 1m 21s Verified: yes Solution Problem Understanding We are asked to maximize Vasya's score in a game where destroying geometric figures earns points based on a per-figure cost and a global factor. Each figure type has a quantity and a point value. The factor starts at 1 and increases at specific thresholds after a certain...

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CF 178A2 - Educational Game

CF 178A2 - Educational Game Rating: 1000 Tags: greedy Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a sequence of non-negative integers representing a game board. The task is to repeatedly perform moves that decrease one number and increase another number two steps ahead. Specifically, in a move we choose an index i where the value is positive and a number of steps t such that...

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LeetCode 2448 - Minimum Cost to Make Array Equal

LeetCode Problem 2448 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Sorting, Prefix Sum Solution This guide will use the weighted median optimization approach, which is the key insight behind solving this problem efficiently within the constraints. Problem Understanding The problem gives us two arrays, nums and cost , each of length n . The nums[i] value represents the current number at index i , and cost[i] represents how expensive...

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LeetCode 2333 - Minimum Sum of Squared Difference

LeetCode Problem 2333 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting, Heap (Priority Queue) Solution I can do that, but the complete guide with all requested sections and the level of detail you specified will exceed a single message limit. I will split it cleanly into multiple parts while preserving your exact formatting requirements. Planned structure: Part 1 Problem Understanding Approaches Algorithm Walkthrough Why the greedy + binary search...

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Codeforces Round 165 (Div. 1)

Codeforces Round 165 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 2/4 | Rating range: 1700-3100 | Time: 7m 2s Problem Name Rating Tags Solve Time Verified B Greenhouse Effect 1700 dp 1m 21s ✓ C Flawed Flow 2100 constructive-algorithms, flows, graphs 2m ✓ D Maximum Waterfall 2600 data-structures, dp, graphs 1m 43s ✗ E String Theory 3100 geometry, math, strings 1m 58s ✗

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MemSQL start[c]up Round 1

MemSQL start[c]up Round 1 Type: Special | Problems: 2 | Verified: 2/2 | Rating range: 1500-2800 | Time: 6m 17s Problem Name Rating Tags Solve Time Verified A Square and Rectangles 1500 implementation 4m 20s ✓ E The Red Button 2800 combinatorics, dfs-and-similar, dsu 1m 57s ✓

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LeetCode 2897 - Apply Operations on Array to Maximize Sum of Squares

LeetCode Problem 2897 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Bit Manipulation Solution Problem Understanding The problem presents an integer array nums and a positive integer k . You can perform a bitwise operation on any two distinct elements of the array any number of times. Specifically, for indices i and j , you update nums[i] to (nums[i] AND nums[j]) and nums[j] to (nums[i] OR nums[j]) . After applying...

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LeetCode 2847 - Smallest Number With Given Digit Product

LeetCode Problem 2847 Difficulty: 🟡 Medium Topics: Math, Greedy Solution LeetCode 2847 - Smallest Number With Given Digit Product Problem Understanding The problem gives us a positive integer n and asks us to construct the smallest positive integer whose digits multiply together to exactly n . For example, if n = 105 , we need to find some integer whose digits have product 105 . One valid choice is 357...

Practice › Codeforces Solutions › Codeforces Round 186 (Div. 2) ›

CF 313E - Ilya and Two Numbers

CF 313E - Ilya and Two Numbers Rating: 2300 Tags: constructive algorithms, data structures, dsu, greedy Solve time: 1m 8s Verified: no Solution Problem4 2

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LeetCode 2712 - Minimum Cost to Make All Characters Equal

LeetCode Problem 2712 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy Solution Problem Understanding The problem gives us a binary string s consisting only of characters '0' and '1' . Our goal is to make every character in the string equal, meaning the final string must become either all '0' characters or all '1' characters. We are allowed to perform two types of operations: Choose an index i and flip...

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LeetCode 2871 - Split Array Into Maximum Number of Subarrays

LeetCode Problem 2871 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem is asking us to split a given array of non-negative integers into contiguous subarrays in a way that maximizes the number of subarrays , while minimizing the sum of their bitwise AND scores . The score of a subarray is defined as the bitwise AND of all elements in that subarray. Since AND-ing any...

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LeetCode 3281 - Maximize Score of Numbers in Ranges

LeetCode Problem 3281 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution Problem Understanding The problem presents a list of intervals derived from the start array and a fixed d . Specifically, each interval is [start[i], start[i] + d] . The goal is to select exactly one integer from each interval such that the minimum absolute difference between any two chosen integers is maximized . In other words, you...

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LeetCode 2706 - Buy Two Chocolates

LeetCode Problem 2706 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem is asking us to purchase exactly two chocolates from a store given their individual prices, while ensuring that after buying them we do not end up in debt. The input consists of an array prices , where each element represents the cost of one chocolate, and an integer money , which is the total money...

Practice › Codeforces Solutions › Codeforces Round 116 (Div. 2, ACM-ICPC Rules) ›

CF 180D - Name

CF 180D - Name Rating: 1900 Tags: greedy, strings Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given a multiset of characters in string s . We may rearrange these characters in any order, but we must use every character exactly once. Among all such permutations, we want the lexicographically smallest string that is still strictly larger than another string t . This is not asking for...

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LeetCode 3282 - Reach End of Array With Max Score

LeetCode Problem 3282 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3282 - Reach End of Array With Max Score Problem Understanding We are given an integer array nums , where each position represents a possible jump starting point. We begin at index 0 and must eventually reach index n - 1 . From any index i , we may jump to any later index j where j > i...

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LeetCode 2587 - Rearrange Array to Maximize Prefix Score

LeetCode Problem 2587 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Prefix Sum Solution Problem Understanding The problem gives us a 0-indexed array of integers , nums , which can include negative numbers, zero, and positive numbers. We are allowed to reorder the elements in any way we choose. After reordering, we compute the prefix sum array , prefix , where prefix[i] is the sum of all elements from index 0...

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CF 144E - Competition

CF 144E - Competition Rating: 2200 Tags: data structures, greedy Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given a triangular region of a square matrix called an n -degree staircase. In this staircase, each cell is accessible except for the area above the secondary diagonal, which runs from the top right to the bottom left. On this staircase, there are m sportsmen placed at distinct positions....

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CF 207A2 - Beaver's Calculator 1.0

CF 207A2 - Beaver's Calculator 1.0 Rating: 1800 Tags: greedy Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given several independent sequences of integers, one sequence per scientist. Each sequence must be kept in its original internal order, but we are allowed to interleave these sequences arbitrarily when forming one global list. Every adjacent pair in the final list is judged as either good or bad depending...

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LeetCode 2530 - Maximal Score After Applying K Operations

LeetCode Problem 2530 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to maximize a score after performing exactly k operations on an array of integers. Each operation allows us to choose any element nums[i] , add its value to the score, and then replace it with its ceiling division by 3. Essentially, every time we pick a number, it decreases for future...

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LeetCode 2842 - Count K-Subsequences of a String With Maximum Beauty

LeetCode Problem 2842 Difficulty: 🔴 Hard Topics: Hash Table, Math, String, Greedy, Sorting, Combinatorics Solution Problem Understanding The problem requires us to count k-subsequences of a string s that have the maximum beauty , where beauty is defined as the sum of the frequency of each character in the subsequence. A k-subsequence is a subsequence of length k where all characters are unique. The input string can be up to...

Practice › Codeforces Solutions › Codeforces Round 159 (Div. 2) ›

CF 257D - Sum

CF 257D - Sum Rating: 1900 Tags: greedy, math Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given a list of integers representing a sequence where each element is at least as large as the previous one but no more than double the previous one. Our task is to assign either a plus or minus sign to each element so that the resulting sum lies between zero...

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Codeforces Round 122 (Div. 1)

Codeforces Round 122 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 3/4 | Rating range: 1700-2900 | Time: 8m 3s Problem Name Rating Tags Solve Time Verified A Cutting Figure 1700 constructive-algorithms, graphs, trees 1m 41s ✓ B Xor 2000 brute-force 1m 53s ✓ C Hamming Distance 2400 constructive-algorithms, greedy, math 2m 31s ✗ D Two Segments 2900 data-structures 1m 58s ✓

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LeetCode 2182 - Construct String With Repeat Limit

LeetCode Problem 2182 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Heap (Priority Queue), Counting Solution Problem Understanding The problem asks us to construct a string from the characters of a given string s under a specific constraint: no character can appear more than repeatLimit times consecutively. The goal is not just to create any valid string but to produce the lexicographically largest one possible. Lexicographic ordering is similar to...

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LeetCode 2566 - Maximum Difference by Remapping a Digit

LeetCode Problem 2566 Difficulty: 🟢 Easy Topics: Math, Greedy Solution Problem Understanding The problem asks us to maximize the difference between two numbers that can be created from a given integer num through a specific remapping operation. We are allowed to choose exactly one digit d1 from 0 through 9 , and replace all occurrences of that digit in num with another digit d2 , which can also be any...

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CF 159A - Friends or Not

CF 159A - Friends or Not Rating: 1400 Tags: *special, greedy, implementation Solve time: 1m 47s Verified: yes Solution Problem Understanding We are given a chronological log of private messages between users in a social network. Each record contains the sender, the receiver, and the timestamp of the message. Two users become friends if one of them replies to the other's message quickly enough. More precisely, suppose user A sends...

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Codeforces Round 162 (Div. 2)

Codeforces Round 162 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1000 | Time: 2m 41s Problem Name Rating Tags Solve Time Verified A Colorful Stones (Simplified Edition) 800 implementation 1m 17s ✗ B Roadside Trees (Simplified Edition) 1000 greedy, implementation 1m 24s ✓

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LeetCode 2472 - Maximum Number of Non-overlapping Palindrome Substrings

LeetCode Problem 2472 Difficulty: 🔴 Hard Topics: Two Pointers, String, Dynamic Programming, Greedy Solution Problem Understanding The problem asks us to find the maximum number of non-overlapping palindrome substrings in a given string s such that each substring has a length of at least k . In other words, we are looking to segment the string into valid palindromic blocks, where no two selected blocks overlap and each block is...

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LeetCode 2497 - Maximum Star Sum of a Graph

LeetCode Problem 2497 Difficulty: 🟡 Medium Topics: Array, Greedy, Graph Theory, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us an undirected graph where each node has an associated integer value. We are asked to form a star graph and compute the maximum possible star sum. A star graph is defined by choosing one node as the center and selecting up to k of its neighbors. The resulting...

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LeetCode 2616 - Minimize the Maximum Difference of Pairs

LeetCode Problem 2616 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem asks us to select exactly p disjoint pairs from the array nums such that the largest difference among all chosen pairs is as small as possible. For every pair (i, j) , the pair difference is defined as: $$|nums[i] - nums[j]|$$ The goal is not to minimize the sum of differences,...

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LeetCode 2571 - Minimum Operations to Reduce an Integer to 0

LeetCode Problem 2571 Difficulty: 🟡 Medium Topics: Dynamic Programming, Greedy, Bit Manipulation Solution Problem Understanding The problem asks us to find the minimum number of operations required to reduce a given positive integer n to 0 , where each operation consists of adding or subtracting a power of two from the current value of n . A power of two is defined as any number of the form $2^i$ where...

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LeetCode 2542 - Maximum Subsequence Score

LeetCode Problem 2542 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution LeetCode 2542 - Maximum Subsequence Score Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , both of the same length n , along with an integer k . We must choose exactly k indices from the arrays. The chosen indices form a subsequence, meaning the selected positions come from the original arrays...

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LeetCode 1936 - Add Minimum Number of Rungs

LeetCode Problem 1936 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us a ladder represented by a strictly increasing array called rungs . Each value in the array represents the height of a rung above the floor. You begin standing on the floor at height 0 , and your goal is to reach the final rung. The restriction is that you can only climb upward if...

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VK Cup 2012 Round 2 (Unofficial Div. 2 Edition)

VK Cup 2012 Round 2 (Unofficial Div. 2 Edition) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1100 | Time: 2m 57s Problem Name Rating Tags Solve Time Verified A Chores 800 sortings 1m 25s ✓ B Replacing Digits 1100 greedy 1m 32s ✓

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LeetCode 3192 - Minimum Operations to Make Binary Array Elements Equal to One II

LeetCode Problem 3192 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding This problem asks us to take a binary array nums , which contains only 0s and 1s, and transform it so that all elements become 1 using the minimum number of allowed operations. The operation is defined as choosing any index i and flipping all elements from that index to the end of the array. Flipping...

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Codeforces Round 168 (Div. 1)

Codeforces Round 168 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 2/2 | Rating range: 1500-1800 | Time: 4m 42s Problem Name Rating Tags Solve Time Verified A k-Multiple Free Set 1500 binary-search, greedy, sortings 1m 14s ✓ B Zero Tree 1800 dfs-and-similar, dp, greedy 3m 28s ✓

Practice › Codeforces Solutions › Codeforces Round 242 (Div. 2) ›

CF 424B - Megacity

CF 424B - Megacity Rating: 1200 Tags: binary search, greedy, implementation, sortings Solve time: 5m 55s Verified: no Solution

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LeetCode 2952 - Minimum Number of Coins to be Added

LeetCode Problem 2952 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the minimum number of coins we need to add to an existing list of coins so that every integer from 1 to a given target can be formed as the sum of some subsequence of the coins. Here, a subsequence is a selection of coins in their original order, but we...

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LeetCode 2818 - Apply Operations to Maximize Score

LeetCode Problem 2818 Difficulty: 🔴 Hard Topics: Array, Math, Stack, Greedy, Sorting, Monotonic Stack, Number Theory Solution Problem Understanding The problem gives us an array nums and an integer k . We begin with a score of 1 , and we are allowed to perform at most k operations. In each operation, we choose a subarray that has not been chosen before. From that subarray, we select the element with...

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CF 219C - Color Stripe

CF 219C - Color Stripe Rating: 1600 Tags: brute force, dp, greedy Solve time: 2m 59s Verified: yes Solution Problem Understanding We are given a stripe consisting of $n$ square cells, each painted in one of $k$ colors. The stripe is represented as a string of uppercase letters, where each letter corresponds to a color. The goal is to repaint some cells so that no two adjacent cells share the...

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LeetCode 2868 - The Wording Game

LeetCode Problem 2868 Difficulty: 🔴 Hard Topics: Array, Math, Two Pointers, String, Greedy, Game Theory Solution Problem Understanding The problem describes a turn-based game between Alice and Bob, where both players have a lexicographically sorted list of words. Alice always starts by playing her lexicographically smallest word , and the players then alternate turns. On each turn, the current player must select a word from their list that is closely...

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CF 296A - Yaroslav and Permutations

CF 296A - Yaroslav and Permutations Rating: 1100 Tags: greedy, math Solve time: 57s Verified: yes Solution Problem Understanding We are given a sequence of integers, and we are allowed to repeatedly swap adjacent elements. Because adjacent swaps can generate any permutation of the array, the real freedom we have is complete reordering of the elements. The target condition is not about a specific arrangement, but about whether we can...

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LeetCode 2591 - Distribute Money to Maximum Children

LeetCode Problem 2591 Difficulty: 🟢 Easy Topics: Math, Greedy Solution Problem Understanding

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Codeforces Round 253 (Div. 1)

Codeforces Round 253 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1800-3100 | Time: 3m 6s Problem Name Rating Tags Solve Time Verified B Andrey and Problem 1800 greedy, math, probabilities 1m 14s ✓ E Gena and Second Distance 3100 geometry 1m 52s ✗

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Croc Champ 2013 - Finals (online version, Div. 1)

Croc Champ 2013 - Finals (online version, Div. 1) Type: Div. 1 | Problems: 4 | Verified: 4/4 | Rating range: 1900-2900 | Time: 12m 12s Problem Name Rating Tags Solve Time Verified A Morning run 2000 binary-search, math, two-pointers 4m 7s ✓ C Memory for Arrays 1900 binary-search, bitmasks, greedy 3m 39s ✓ D Tennis Rackets 2700 brute-force, geometry 1m 52s ✓ E Sheep 2900 binary-search, greedy 2m 34s...

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CF 276C - Little Girl and Maximum Sum

CF 276C - Little Girl and Maximum Sum Rating: 1500 Tags: data structures, greedy, implementation, sortings Solve time: 1m 42s Verified: yes Solution Problem Understanding We are given an array and several range queries. Each query asks for the sum of all elements between two indices. The unusual part is that we are allowed to rearrange the array before answering the queries, and we want the total of all query...

Practice › Codeforces Solutions › Codeforces Round 238 (Div. 2) ›

CF 405A - Gravity Flip

CF 405A - Gravity Flip Rating: 900 Tags: greedy, implementation, sortings Solve time: 6m 21s Verified: no Solution Problem Understanding We are given a row of vertical stacks of cubes, where each position holds a certain number of cubes. You can think of this as an array where each index represents a column and the value is its height. Initially, gravity acts downward, so cubes are stacked vertically inside each...

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Codeforces Round 148 (Div. 1)

Codeforces Round 148 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1300-2900 | Time: 16m 8s Problem Name Rating Tags Solve Time Verified A Not Wool Sequences 1300 constructive-algorithms, math 5m 18s ✓ B Boring Partition 1800 constructive-algorithms 3m 56s ✓ C World Eater Brothers 2100 dfs-and-similar, dp, greedy 2m 5s ✓ D Tape Programming 2900 data-structures, implementation 1m 30s ✓ E Meeting Her...

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Codeforces Round 109 (Div. 1)

Codeforces Round 109 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 4/4 | Rating range: 1600-2400 | Time: 6m 30s Problem Name Rating Tags Solve Time Verified A Hometask 1600 greedy 1m 15s ✓ B Colliders 1600 math, number-theory 2m 4s ✓ C Double Profiles 2300 graphs, hashing, sortings 1m 37s ✓ D Flatland Fencing 2400 games, math 1m 34s ✓

Practice › Codeforces Solutions › Codeforces Round 158 (Div. 2) ›

CF 260C - Balls and Boxes

CF 260C - Balls and Boxes Rating: 1700 Tags: constructive algorithms, greedy, implementation Solve time: 1m 20s Verified: no Solution Problem Understanding We are given the final state of a row of boxes after a very specific operation was applied exactly once in reverse history. Originally, each box contained some number of balls. One box was chosen, emptied completely, and its balls were redistributed one by one starting from the...

Practice › Codeforces Solutions › Codeforces Round 240 (Div. 1) ›

CF 414D - Mashmokh and Water Tanks

CF 414D - Mashmokh and Water Tanks Rating: 2300 Tags: binary search, data structures, greedy, trees, two pointers Solve time: 1m 43s Verified: no Solution Problem Understanding We are given a rooted tree where each vertex represents a water tank. Initially all tanks are empty, but we are allowed to place up to $k$ liters of water, each liter placed into a distinct non-root node. After that, the process runs...

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LeetCode 1850 - Minimum Adjacent Swaps to Reach the Kth Smallest Number

LeetCode Problem 1850 Difficulty: 🟡 Medium Topics: Two Pointers, String, Greedy Solution Problem Understanding The problem asks us to compute the minimum number of adjacent swaps needed to transform a given number num into the kth smallest wonderful integer . A wonderful integer is any permutation of num 's digits that is strictly greater than num . Among all such permutations, we only care about the kth smallest one. The...

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CF 316A1 - Special Task

CF 316A1 - Special Task Rating: 1100 Tags: greedy Solve time: 1m 30s Verified: no Solution Problem Understanding We are given a string that represents a partially specified code. Each position in the string contributes constraints on what digit can appear there. Some positions are fixed digits, some are wildcards, and some are letter constraints that enforce equality or inequality between positions. A question mark means we are free to...

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LeetCode 2375 - Construct Smallest Number From DI String

LeetCode Problem 2375 Difficulty: 🟡 Medium Topics: String, Backtracking, Stack, Greedy Solution Problem Understanding The problem asks us to construct the lexicographically smallest number from a string pattern consisting of 'I' and 'D' . Each character in the pattern defines a relationship between consecutive digits of the number: 'I' indicates that the next digit should be larger than the current, and 'D' indicates the next digit should be smaller ....

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Codeforces Round 158 (Div. 2)

Codeforces Round 158 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 0/3 | Rating range: 1400-2100 | Time: 5m 48s Problem Name Rating Tags Solve Time Verified A Adding Digits 1400 implementation, math 1m 21s ✗ C Balls and Boxes 1700 constructive-algorithms, greedy, implementation 1m 20s ✗ D Black and White Tree 2100 constructive-algorithms, dsu, graphs 3m 7s ✗

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Codeforces Round 241 (Div. 2)

Codeforces Round 241 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1300-2500 | Time: 8m 12s Problem Name Rating Tags Solve Time Verified A Guess a number! 1400 greedy, implementation, two-pointers 1m 47s ✗ B Art Union 1300 brute-force, dp, implementation 1m 26s ✓ C Booking System 1600 binary-search, dp, greedy 1m 32s ✓ D Population Size 2400 greedy, implementation, math 1m 23s ✓...

Practice › Codeforces Solutions › Codeforces Round 159 (Div. 2) ›

CF 257A - Sockets

CF 257A - Sockets Rating: 1100 Tags: greedy, implementation, sortings Solve time: 1m 10s Verified: yes Solution Problem Understanding Vasya has a set of electrical devices and a limited number of wall sockets in his flat. Additionally, he owns multiple supply-line filters, each of which provides extra sockets but occupies one itself when plugged in. The task is to determine the minimum number of supply-line filters Vasya needs to plug...

Practice › Codeforces Solutions › Codeforces Round 140 (Div. 1) ›

CF 226B - Naughty Stone Piles

CF 226B - Naughty Stone Piles Rating: 1900 Tags: greedy Solve time: 2m 22s Verified: yes Solution Problem Understanding We have several stone piles, each with some initial size. One operation chooses a source pile and merges it into another pile. The source pile disappears, the destination pile grows, and the operation cost equals the current size of the source pile. The unusual restriction is on the destination side. Every...

Practice › Codeforces Solutions ›

Codeforces Round 199 (Div. 2)

Codeforces Round 199 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 1200-2400 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Xenia and Divisors 1200 greedy, implementation 6m 2s ✗ C Cupboard and Balloons 1900 geometry 5m 17s ✓ E Xenia and Tree 2400 data-structures, divide-and-conquer, trees 5m 12s ✓

Practice › Codeforces Solutions ›

Codeforces Round 142 (Div. 2)

Codeforces Round 142 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1300 | Time: 4m 23s Problem Name Rating Tags Solve Time Verified A Dragons 1000 greedy, sortings 3m 28s ✓ B T-primes 1300 binary-search, implementation, math 55s ✓

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2195 - Append K Integers With Minimal Sum

LeetCode Problem 2195 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting Solution Problem Understanding The problem asks us to append k unique positive integers to an existing array nums such that none of the integers we add are already in nums , and the sum of the numbers we append is minimized. In other words, we want to pick the smallest k positive integers that are missing from nums ....

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LeetCode 3216 - Lexicographically Smallest String After a Swap

LeetCode Problem 3216 Difficulty: 🟢 Easy Topics: String, Greedy Solution Problem Understanding The problem requires transforming a string of digits into its lexicographically smallest form by performing at most one swap between adjacent digits of the same parity . Here, parity refers to whether a digit is even or odd. Two digits can only be swapped if both are odd or both are even. The input is a string s...

Practice › Codeforces Solutions › Codeforces Round 139 (Div. 2) ›

CF 225B - Well-known Numbers

CF 225B - Well-known Numbers Rating: 1600 Tags: binary search, greedy, number theory Solve time: 3m 27s Verified: no Solution Problem Understanding We are given two integers, s and k . The task is to express s as a sum of distinct numbers taken from the k -bonacci sequence. The sequence behaves like Fibonacci, but instead of summing the previous two values, each term is the sum of the previous...

Practice › Codeforces Solutions › Codeforces Round 184 (Div. 2) ›

CF 305C - Ivan and Powers of Two

CF 305C - Ivan and Powers of Two Rating: 1600 Tags: greedy, implementation Solve time: 1m 48s Verified: yes Solution Problem Understanding We are given a sorted array of exponents. Instead of the exponents themselves, Ivan writes the corresponding powers of two on paper: $$2^{a_1}, 2^{a_2}, \dots, 2^{a_n}$$ We may add more numbers, but every added number must also be a power of two. The goal is to make the...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2098 - Subsequence of Size K With the Largest Even Sum

LeetCode Problem 2098 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to find the largest possible even sum of a subsequence of length k from a given integer array nums . A subsequence is a sequence that can be obtained by deleting some elements from the array without changing the relative order of the remaining elements. The input consists of an array of integers...

Practice › Codeforces Solutions › Codeforces Round 152 (Div. 2) ›

CF 248D - Sweets for Everyone!

CF 248D - Sweets for Everyone! Rating: 2300 Tags: binary search, greedy, implementation Solve time: 3m 8s Verified: yes Solution Problem Understanding We are given a one-dimensional street made of n consecutive sections. Each section is either a house that must receive exactly one kilogram of sweets, a shop that can provide at most one kilogram of sweets, or empty space that only matters for movement. Movement happens step-by-step between...

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LeetCode 2234 - Maximum Total Beauty of the Gardens

LeetCode Problem 2234 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Greedy, Sorting, Enumeration, Prefix Sum Solution Problem Understanding In this problem, we are given several gardens, where flowers[i] represents how many flowers are already planted in the i-th garden. We are also given a limited number of additional flowers, newFlowers , that we may distribute among the gardens. The goal is to maximize the total beauty score after...

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LeetCode 2064 - Minimized Maximum of Products Distributed to Any Store

LeetCode Problem 2064 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy Solution Problem Understanding The problem gives us n retail stores and an array quantities , where each element represents how many products exist for a particular product type. The important restriction is that a single store may contain products from only one product type. However, a product type may be split across multiple stores. Our goal is to distribute...

Practice › Codeforces Solutions › VK Cup 2012 Round 3 (Unofficial Div. 2 Edition) ›

CF 174B - File List

CF 174B - File List Rating: 1400 Tags: dp, greedy, implementation Solve time: 3m 40s Verified: yes Solution Problem Understanding We are given one long string that originally consisted of several file names written back to back with no separators. Every valid file name must look like name.ext . The rules are strict. The part before the dot contains only lowercase letters and has length from 1 to 8. The...

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LeetCode 3086 - Minimum Moves to Pick K Ones

LeetCode Problem 3086 Difficulty: 🔴 Hard Topics: Array, Greedy, Sliding Window, Prefix Sum Solution Exploration The reviewer identified a sign error in the swap argument, so the first task is to determine the correct monotonicity direction before rebuilding the proof. For $n=1$, there is only one permutation, so the statement is trivial. For $n=2$, take $$x_1=5,\quad x_2=2,\quad y_1=4,\quad y_2=1.$$ The ordered pairing gives $$(5-4)^2+(2-1)^2=1+1=2.$$ The swapped pairing gives $$(5-1)^2+(2-4)^2=16+4=20.$$ Thus...

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LeetCode 2486 - Append Characters to String to Make Subsequence

LeetCode Problem 2486 Difficulty: 🟡 Medium Topics: Two Pointers, String, Greedy Solution Problem Understanding The problem asks us to determine the minimum number of characters that need to be appended to the end of string s so that string t becomes a subsequence of s . A subsequence is a sequence that appears in the same order as in another string, but not necessarily consecutively. Essentially, we are allowed to...

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LeetCode 2645 - Minimum Additions to Make Valid String

LeetCode Problem 2645 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Stack, Greedy Solution Problem Understanding This problem asks us to determine the minimum number of insertions needed to transform a given string word into a valid string . A valid string is defined as one that can be formed by concatenating the sequence "abc" one or more times. In other words, every valid string follows the repeating pattern: abcabcabc... We...

Practice › Codeforces Solutions ›

Croc Champ 2013 - Round 2

Croc Champ 2013 - Round 2 Type: Special | Problems: 4 | Verified: 4/4 | Rating range: 1500-2700 | Time: 8m 33s Problem Name Rating Tags Solve Time Verified A Weird Game 1500 games, greedy 53s ✓ C Cube Problem 2400 brute-force, math, number-theory 1m 36s ✓ D Ksusha and Square 2700 geometry, math, probabilities 1m 59s ✓ E Close Vertices 2700 data-structures, divide-and-conquer, trees 4m 5s ✓

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2078 - Two Furthest Houses With Different Colors

LeetCode Problem 2078 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem is asking us to find the maximum distance between two houses that have different colors . You are given a 0-indexed list colors where each element represents the color of a house. The distance between two houses at indices i and j is defined as abs(i - j) - the absolute difference of their indices. The...

Practice › Codeforces Solutions › Codeforces Round 190 (Div. 2) ›

CF 322A - Ciel and Dancing

CF 322A - Ciel and Dancing Rating: 1000 Tags: greedy Solve time: 1m 48s Verified: yes Solution Problem Understanding We are given a group of boys and girls who will participate in a sequence of dances. Each dance pairs exactly one boy with one girl. The restriction is about novelty: in any valid pair, at least one participant must be dancing for the first time in the entire sequence. This...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2522 - Partition String Into Substrings With Values at Most K

LeetCode Problem 2522 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy Solution LeetCode 2522 - Partition String Into Substrings With Values at Most K Problem Understanding The problem gives us a numeric string s , where every character is a digit between '1' and '9' , and an integer k . We must split the string into contiguous substrings such that every substring, when interpreted as an integer, has a...

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245C - Game with Coins

CF 245C - Game with Coins Rating: 1700 Tags: greedy Solve time: 1m 37s Verified: yes Solution Problem Understanding We are given a line of numbered chests, each containing some number of coins. On each move, a player chooses an integer position $x$, and that move simultaneously affects three specific chests: $x$, $2x$, and $2x+1$. From each of these chests, one coin is removed if it exists. The game ends...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2193 - Minimum Number of Moves to Make Palindrome

LeetCode Problem 2193 Difficulty: 🔴 Hard Topics: Two Pointers, String, Greedy, Binary Indexed Tree Solution LeetCode 2193 - Minimum Number of Moves to Make Palindrome Problem Understanding This problem asks us to transform a given string into a palindrome using the minimum number of adjacent swaps. A palindrome is a string that reads the same forward and backward. For example, "abba" and "racecar" are palindromes. The only operation allowed is...

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LeetCode 2892 - Minimizing Array After Replacing Pairs With Their Product

LeetCode Problem 2892 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem gives us an integer array nums and a value k . We are allowed to repeatedly merge adjacent elements under one condition: If two adjacent values x and y satisfy x * y <= k , then we may replace them with a single value equal to x * y . Each operation reduces...

Practice › Codeforces Solutions › Codeforces Round 121 (Div. 1) ›

CF 191D - Metro Scheme

CF 191D - Metro Scheme Rating: 2700 Tags: graphs, greedy Solve time: 1m 59s Verified: yes Solution Problem Understanding We are given an undirected connected graph describing a subway system. Every edge is a tunnel, every vertex is a station. The graph is guaranteed to be a vertex cactus, meaning each vertex belongs to at most one simple cycle. The subway is composed of lines of two possible types. A...

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LeetCode 3068 - Find the Maximum Sum of Node Values

LeetCode Problem 3068 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Bit Manipulation, Tree, Sorting Solution Problem Understanding You are given a tree with n nodes. Every node has a value stored in the array nums , and every edge connects two nodes in an undirected manner. You may repeatedly perform the following operation on any edge [u, v] : Replace nums[u] with nums[u] XOR k Replace nums[v] with nums[v]...

Practice › Codeforces Solutions › VK Cup 2012 Round 2 (Unofficial Div. 2 Edition) ›

CF 169B - Replacing Digits

CF 169B - Replacing Digits Rating: 1100 Tags: greedy Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given a decimal number as a string and another string containing extra digits that we may use for replacements. Every digit from the second string can be used at most once. For each chosen digit, we may replace any single position in the original number. The goal is to maximize...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2038 - Remove Colored Pieces if Both Neighbors are the Same Color

LeetCode Problem 2038 Difficulty: 🟡 Medium Topics: Math, String, Greedy, Game Theory Solution Problem Understanding This problem describes a two-player game played on a line of colored pieces. The input colors is a string representing these pieces, where each character is either 'A' or 'B' . Alice always moves first and can only remove 'A' pieces that are surrounded on both sides by 'A' . Bob moves second and can...

Practice › Codeforces Solutions › Croc Champ 2012 - Round 1 ›

CF 173D - Deputies

CF 173D - Deputies Rating: 2500 Tags: constructive algorithms, graphs, greedy, implementation Solve time: 3m 4s Verified: yes Solution Problem Understanding We are asked to assign k deputies to n cities, with the condition that each deputy manages exactly three cities. The cities are placed on two sides of a river, and some pairs of cities are connected by bridges that span the river. No deputy may manage two cities...

Practice › Codeforces Solutions ›

Codeforces Round 128 (Div. 2)

Codeforces Round 128 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2300 | Time: 6m 39s Problem Name Rating Tags Solve Time Verified A Two Problems 1200 brute-force, implementation 1m 6s ✓ B Game on Paper 1300 brute-force, implementation 1m 41s ✓ C Photographer 1400 greedy, sortings 1m 5s ✓ D Hit Ball 1700 geometry, implementation, math 1m 20s ✗ E Transportation 2300 greedy,...

Practice › Codeforces Solutions › CROC-MBTU 2012, Elimination Round (ACM-ICPC) ›

CF 245D - Restoring Table

CF 245D - Restoring Table Rating: 1500 Tags: constructive algorithms, greedy Solve time: 3m 10s Verified: yes Solution Problem Understanding We are given a square table that was originally generated from a hidden array of non-negative integers. Each off-diagonal entry is the bitwise AND of the corresponding pair of hidden values, while diagonal entries are artificially replaced by -1. The task is to reconstruct any valid hidden array that could...

Practice › Codeforces Solutions › Codeforces Round 105 (Div. 2) ›

CF 148C - Terse princess

CF 148C - Terse princess Rating: 1700 Tags: constructive algorithms, greedy Solve time: 2m 14s Verified: no Solution Problem Understanding We need to construct an array of groom fortunes so that the princess reacts in exactly the required way. For every groom after the first one, two special situations are possible. If the current fortune is larger than every previous fortune, the princess says Oh... . If the current fortune...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2589 - Minimum Time to Complete All Tasks

LeetCode Problem 2589 Difficulty: 🔴 Hard Topics: Array, Binary Search, Stack, Greedy, Sorting Solution Problem Understanding This problem is asking us to determine the minimum amount of time that a computer must be turned on to execute a set of tasks, given that each task has a specified time window [starti, endi] and requires a total duration durationi that does not need to be continuous. In other words, the computer...

Practice › Codeforces Solutions ›

Croc Champ 2012 - Round 2

Croc Champ 2012 - Round 2 Type: Special | Problems: 4 | Verified: 4/4 | Rating range: 1200-3100 | Time: 6m 33s Problem Name Rating Tags Solve Time Verified A Trading Business 1200 greedy, sortings 1m 11s ✓ B Word Cut 1700 dp 1m 42s ✓ C Playing with Superglue 2000 combinatorics, constructive-algorithms 1m 28s ✓ E Archaeology 3100 data-structures, dfs-and-similar, trees 2m 12s ✓

Practice › Codeforces Solutions ›

Codeforces Round 131 (Div. 1)

Codeforces Round 131 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1700-2700 | Time: 7m 23s Problem Name Rating Tags Solve Time Verified A Game 1700 dfs-and-similar, greedy 52s ✓ B Numbers 1900 combinatorics, dp 54s ✗ C Relay Race 2000 dp 2m 58s ✓ D Stars 2300 constructive-algorithms, geometry 1m 36s ✗ E Two Permutations 2700 data-structures, hashing, strings 1m 3s ✓

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2541 - Minimum Operations to Make Array Equal II

LeetCode Problem 2541 Difficulty: 🟡 Medium Topics: Array, Math, Greedy Solution

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3362 - Zero Array Transformation III

LeetCode Problem 3362 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum Solution Problem Understanding We are given an integer array nums and a list of interval queries. Each query [l, r] allows us to reduce every element inside that range by at most 1 . The important detail is that the decrement is optional and independent for every index in the range. This means...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2436 - Minimum Split Into Subarrays With GCD Greater Than One

LeetCode Problem 2436 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Greedy, Number Theory Solution Problem Understanding The problem requires splitting a given array of positive integers into contiguous subarrays such that the greatest common divisor (GCD) of each subarray is strictly greater than 1. The goal is to minimize the number of subarrays after splitting. In simpler terms, we need to partition the array into the fewest contiguous segments...

Practice › Codeforces Solutions › Codeforces Round 254 (Div. 1) ›

CF 444A - DZY Loves Physics

CF 444A - DZY Loves Physics Rating: 1600 Tags: greedy, math Solve time: 1m 32s Verified: yes Solution Problem Understanding We are given an undirected graph where each vertex carries a positive weight and each edge also carries a positive weight. From this graph we are allowed to pick a subset of vertices, but we are not free to pick them arbitrarily: the chosen vertices must form a connected induced...

Practice › Codeforces Solutions ›

Codeforces Round 119 (Div. 1)

Codeforces Round 119 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1500-2900 | Time: 10m 3s Problem Name Rating Tags Solve Time Verified A Permutations 1500 greedy 1m 30s ✓ B AlgoRace 1800 dp, shortest-paths 2m 5s ✓ C Weak Memory 2000 dfs-and-similar, dsu 2m 12s ✓ D BRT Contract 2800 data-structures 1m 54s ✓ E Heaven Tour 2900 data-structures, greedy 2m 22s ✗

Practice › Codeforces Solutions ›

Codeforces Round 206 (Div. 1)

Codeforces Round 206 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1500-2900 | Time: 15m 26s Problem Name Rating Tags Solve Time Verified A Vasya and Robot 1500 brute-force, greedy, math 2m 39s ✓ B Game with Strings 2400 bitmasks, dp, games 2m 1s ✗ C Vasya and Beautiful Arrays 2100 brute-force, dp, number-theory 2m 47s ✓ D Transferring Pyramid 2900 dp 2m 46s...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2335 - Minimum Amount of Time to Fill Cups

LeetCode Problem 2335 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array amount of length 3 . Each index represents the number of cups that need to be filled for a specific water type: amount[0] represents cold water cups amount[1] represents warm water cups amount[2] represents hot water cups Every second, the machine can perform exactly one of these operations:...

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LeetCode 2241 - Design an ATM Machine

LeetCode Problem 2241 Difficulty: 🟡 Medium Topics: Array, Greedy, Design Solution Problem Understanding The problem asks us to design a simulation of an ATM machine that can handle deposits and withdrawals with strict rules about how money is dispensed. The ATM stores five types of banknotes: $20, $50, $100, $200, and $500. The key challenge is implementing the withdrawal logic, which prioritizes giving out larger denominations first. The deposit function...

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LeetCode 2957 - Remove Adjacent Almost-Equal Characters

LeetCode Problem 2957 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy Solution LeetCode 2957 - Remove Adjacent Almost-Equal Characters Problem Understanding We are given a string word consisting of lowercase English letters. Two adjacent characters are considered almost-equal if either: They are exactly the same, such as 'a' and 'a' Their positions in the alphabet differ by exactly one, such as 'a' and 'b' , 'c' and 'b' , 'x'...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2600 - K Items With the Maximum Sum

LeetCode Problem 2600 Difficulty: 🟢 Easy Topics: Math, Greedy Solution Problem Understanding The problem asks us to determine the maximum possible sum when picking exactly k items from a bag containing items labeled 1 , 0 , or -1 . The bag's composition is given by three non-negative integers: numOnes for the number of 1 s, numZeros for the number of 0 s, and numNegOnes for the number of -1...

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LeetCode 2498 - Frog Jump II

LeetCode Problem 2498 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy Solution Problem Understanding The problem gives us a sorted array stones , where each value represents the position of a stone in a river. The frog starts on the first stone, which is always at position 0 , and must travel to the last stone and then eventually return to the first stone. The important restriction is that every...

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LeetCode 2557 - Maximum Number of Integers to Choose From a Range II

LeetCode Problem 2557 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution Problem Understanding The problem is asking to select the maximum number of integers from the range [1, n] under several constraints. First, integers in the banned array cannot be chosen. Second, each integer can be chosen at most once. Third, the sum of all chosen integers must not exceed maxSum . The goal is to determine the...

Practice › Codeforces Solutions › Codeforces Round 147 (Div. 2) ›

CF 237D - T-decomposition

CF 237D - T-decomposition Rating: 2000 Tags: dfs and similar, graphs, greedy, trees Solve time: 2m 14s Verified: yes Solution Problem Understanding We are given a tree $s$ with $n$ vertices. We must construct another tree $t$, whose nodes are subsets of vertices of $s$. Each subset is usually called a bag. The decomposition must satisfy three conditions. First, every original vertex must appear in at least one bag. Second,...

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LeetCode 2410 - Maximum Matching of Players With Trainers

LeetCode Problem 2410 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding This problem requires us to maximize the number of matchings between players and trainers under the condition that a player's ability cannot exceed the trainer's training capacity. In other words, a player i can only be assigned to trainer j if players[i] <= trainers[j] . Additionally, each player and each trainer can participate in at...

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CROC-MBTU 2012, Elimination Round (ACM-ICPC)

CROC-MBTU 2012, Elimination Round (ACM-ICPC) Type: ICPC/IOI | Problems: 8 | Verified: 8/8 | Rating range: 800-2200 | Time: 18m 42s Problem Name Rating Tags Solve Time Verified A System Administrator 800 implementation 3m 27s ✓ B Internet Address 1100 implementation, strings 1m 53s ✓ C Game with Coins 1700 greedy 1m 37s ✓ D Restoring Table 1500 constructive-algorithms, greedy 3m 10s ✓ E Mishap in Club 1400 greedy, implementation...

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LeetCode 3326 - Minimum Division Operations to Make Array Non Decreasing

LeetCode Problem 3326 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Number Theory Solution Problem Understanding The problem asks us to make a given integer array nums non-decreasing by performing a specific type of operation any number of times. Each operation consists of selecting an element and dividing it by its greatest proper divisor . A proper divisor of a number x is a positive integer less than x that divides...

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LeetCode 2813 - Maximum Elegance of a K-Length Subsequence

LeetCode Problem 2813 Difficulty: 🔴 Hard Topics: Array, Hash Table, Stack, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem presents a 0-indexed 2D array items of length n , where each element represents an item with two values: a profit and a category. You are asked to select exactly k items to form a subsequence . A subsequence preserves the original order of items but can skip elements....

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Codeforces Round 242 (Div. 2)

Codeforces Round 242 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: 900-2500 | Time: 20m 42s Problem Name Rating Tags Solve Time Verified A Squats 900 implementation 57s ✗ B Megacity 1200 binary-search, greedy, implementation 5m 55s ✗ C Magic Formulas 1600 math 6m ✗ D Biathlon Track 2300 binary-search, brute-force, constructive-algorithms 1m 21s ✗ E Colored Jenga 2500 dfs-and-similar, dp, probabilities 6m 29s...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2259 - Remove Digit From Number to Maximize Result

LeetCode Problem 2259 Difficulty: 🟢 Easy Topics: String, Greedy, Enumeration Solution LeetCode 2259 - Remove Digit From Number to Maximize Result Problem Understanding The problem gives us a string called number , which represents a positive integer, and a character digit , which is guaranteed to appear at least once inside number . Our task is to remove exactly one occurrence of digit from the string so that the resulting...

Practice › Codeforces Solutions › Codeforces Round 161 (Div. 2) ›

CF 263B - Squares

CF 263B - Squares Rating: 900 Tags: greedy, implementation, sortings Solve time: 3m 7s Verified: no Solution

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3139 - Minimum Cost to Equalize Array

LeetCode Problem 3139 Difficulty: 🔴 Hard Topics: Array, Greedy, Enumeration Solution Problem Understanding This problem asks us to determine the minimum cost to make all elements in an array equal. You are allowed two types of operations: increment a single element at a cost of cost1 , or increment any two distinct elements simultaneously at a cost of cost2 . The goal is to compute the cheapest sequence of these...

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Codeforces Round 132 (Div. 2)

Codeforces Round 132 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 900-2100 | Time: 8m 51s Problem Name Rating Tags Solve Time Verified A Bicycle Chain 900 brute-force, implementation 1m 25s ✓ B Olympic Medal 1300 greedy, math 1m 43s ✓ C Crosses 2100 brute-force, implementation 1m 39s ✓ D Hot Days 1900 greedy 1m 6s ✓ E Periodical Numbers 2100 combinatorics, dp, number-theory...

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LeetCode 2216 - Minimum Deletions to Make Array Beautiful

LeetCode Problem 2216 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy Solution Problem Understanding The problem asks us to transform a given integer array nums into a beautiful array using the minimum number of deletions. A beautiful array satisfies two conditions: its length is even, and no two consecutive elements at even indices are equal ( nums[i] != nums[i + 1] for all i % 2 == 0 ). Deletions are...

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LeetCode 3091 - Apply Operations to Make Sum of Array Greater Than or Equal to k

LeetCode Problem 3091 Difficulty: 🟡 Medium Topics: Math, Greedy, Enumeration Solution Problem Understanding The problem gives us a single positive integer k . We start with an array containing exactly one element: nums = [1] We are allowed to perform two kinds of operations any number of times: Increase the value of any existing element by 1 Duplicate any existing element and append the duplicate to the array Our goal...

Practice › Codeforces Solutions › ABBYY Cup 2.0 - Hard ›

CF 178A3 - Educational Game

CF 178A3 - Educational Game Rating: 1100 Tags: greedy Solve time: 1m 58s Verified: yes Solution Problem Understanding We have an array of non-negative integers. In one move, we pick an index i with a[i] > 0 , decrease a[i] by 1 , and increase some position j by 1 , where j - i must be even and j >= i . The parity restriction is the core of...

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LeetCode 2910 - Minimum Number of Groups to Create a Valid Assignment

LeetCode Problem 2910 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution LeetCode 2910 - Minimum Number of Groups to Create a Valid Assignment Problem Understanding This problem gives us an array of integers representing balls. Balls with the same value are indistinguishable for grouping purposes, and every group must contain balls of only one value. The challenge comes from the balancing constraint. If we create multiple groups, the largest...

Practice › Codeforces Solutions › Croc Champ 2012 - Round 2 ›

CF 176A - Trading Business

CF 176A - Trading Business Rating: 1200 Tags: greedy, sortings Solve time: 1m 11s Verified: yes Solution Problem Understanding Qwerty wants to maximize profit by buying items on one planet and selling them on another. Each planet offers multiple types of items, with known buying and selling prices and stock limits. Qwerty's ship has a fixed capacity, so he cannot carry more than k items. He can buy at most...

Practice › Codeforces Solutions › Codeforces Round 106 (Div. 2) ›

CF 149C - Division into Teams

CF 149C - Division into Teams Rating: 1500 Tags: greedy, math, sortings Solve time: 1m 40s Verified: no Solution Problem Understanding We have a group of boys, each with a skill level in football. The task is to split them into two teams such that the teams are nearly equal in size and the total skill levels of the teams are roughly balanced. Formally, if there are n boys, we...

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CF 159E - Zebra Tower

CF 159E - Zebra Tower Rating: 1700 Tags: *special, data structures, greedy, sortings Solve time: 2m 2s Verified: yes Solution Problem Understanding We have n cubes. Every cube has a color and a size. We want to build a tower using cubes from exactly two distinct colors, and adjacent cubes in the tower must always have different colors. There are no restrictions on cube sizes or ordering. A smaller cube...

Practice › Codeforces Solutions › Codeforces Round 119 (Div. 1) ›

CF 187E - Heaven Tour

CF 187E - Heaven Tour Rating: 2900 Tags: data structures, greedy Solve time: 2m 22s Verified: no Solution Problem Understanding We have n people placed on a line at strictly increasing coordinates. PMP starts at person s , which immediately counts as visited. Every later move must go either strictly left or strictly right, depending on the ticket used for that move. A left ticket allows moving from a larger...

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Codeforces Round 102 (Div. 1)

Codeforces Round 102 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-3000 | Time: 13m 21s Problem Name Rating Tags Solve Time Verified A Help Farmer 1600 brute-force, math 1m 53s ✓ B Help General 1800 constructive-algorithms, greedy, implementation 1m 38s ✓ C Help Caretaker 2300 brute-force, dp 1m 30s ✓ D Help Shrek and Donkey 2 2600 games 2m 34s ✓ E Help...

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Codeforces Round 238 (Div. 2)

Codeforces Round 238 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 0/4 | Rating range: 900-2300 | Time: 15m 46s Problem Name Rating Tags Solve Time Verified A Gravity Flip 900 greedy, implementation, sortings 6m 21s ✗ B Domino Effect 1100 - 1m 23s ✗ C Unusual Product 1600 implementation, math 1m 27s ✗ E Graph Cutting 2300 dfs-and-similar, graphs 6m 35s ✗

Practice › Codeforces Solutions › Codeforces Round 111 (Div. 2) ›

CF 160B - Unlucky Ticket

CF 160B - Unlucky Ticket Rating: 1100 Tags: greedy, sortings Solve time: 1m 29s Verified: yes Solution Problem Understanding We are given a ticket represented as a string of 2_n_ digits, where n is between 1 and 100. The first half of the ticket contains the first n digits and the second half contains the remaining n digits. We are asked to determine whether the ticket is “definitely unlucky.” A...

Practice › Codeforces Solutions › Codeforces Round 142 (Div. 2) ›

CF 230A - Dragons

CF 230A - Dragons Rating: 1000 Tags: greedy, sortings Solve time: 3m 28s Verified: yes Solution Problem Understanding Kirito starts with some initial strength and must defeat every dragon on the level. Each dragon has two values: the minimum strength needed to beat it, and the bonus strength Kirito gains afterward. A fight is only possible if Kirito's current strength is strictly greater than the dragon's strength. Equal strength is...

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LeetCode 2086 - Minimum Number of Food Buckets to Feed the Hamsters

LeetCode Problem 2086 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Greedy Solution Problem Understanding The problem is asking us to place the minimum number of food buckets on empty spaces in a linear arrangement of cells so that all hamsters are fed. Each cell in the string hamsters represents either a hamster ( 'H' ) or an empty spot ( '.' ). A hamster can eat if there is at...

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Codeforces Round 129 (Div. 2)

Codeforces Round 129 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 900-1400 | Time: 2m 24s Problem Name Rating Tags Solve Time Verified A Little Elephant and Rozdil 900 brute-force, implementation 54s ✓ B Little Elephant and Sorting 1400 brute-force, greedy 1m 30s ✓

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LeetCode 3014 - Minimum Number of Pushes to Type Word I

LeetCode Problem 3014 Difficulty: 🟢 Easy Topics: Math, String, Greedy Solution LeetCode 3014 - Minimum Number of Pushes to Type Word I Problem Understanding We are given a word consisting of distinct lowercase English letters. We are allowed to completely redesign the mapping of letters onto the telephone keypad keys 2 through 9 . There are 8 available keys ( 2 to 9 ). Each letter must be assigned to...

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LeetCode 1927 - Sum Game

LeetCode Problem 1927 Difficulty: 🟡 Medium Topics: Math, String, Greedy, Game Theory Solution Problem Understanding The problem describes a two player game played on a numeric string of even length. The string contains digits and possibly some '?' characters. Alice and Bob alternate turns replacing one '?' with a digit from '0' to '9' . Alice moves first. At the end of the game, every '?' has been replaced. The...

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LeetCode 3292 - Minimum Number of Valid Strings to Form Target II

LeetCode Problem 3292 Difficulty: 🔴 Hard Topics: Array, String, Binary Search, Dynamic Programming, Greedy, Segment Tree, Rolling Hash, String Matching, Hash Function Solution LeetCode 3292 - Minimum Number of Valid Strings to Form Target II Problem Understanding We are given a collection of strings words and a target string target . A string is considered valid if it is a prefix of at least one word in words . This...

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LeetCode 1899 - Merge Triplets to Form Target Triplet

LeetCode Problem 1899 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks whether it is possible to create a specific target triplet [x, y, z] as an element of a given list of triplets by repeatedly merging pairs of triplets using a component-wise maximum operation . Each triplet is a list of three integers, representing values along three dimensions. The operation allows us to choose any two...

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LeetCode 2139 - Minimum Moves to Reach Target Score

LeetCode Problem 2139 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to transform the integer 1 into the integer target using the minimum number of moves. At every move, we are allowed to perform one of two operations: Increment the current number by 1 Double the current number The important restriction is that the doubling operation can only be used at most maxDoubles times. Increment...

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CF 325E - The Red Button

CF 325E - The Red Button Rating: 2800 Tags: combinatorics, dfs and similar, dsu, graphs, greedy Solve time: 1m 57s Verified: yes Solution Problem Understanding We are asked to construct a walk on a directed functional graph defined by a very specific transition rule. Each state is a node from 0 to n − 1. From a current node i, the next state is not arbitrary: it must be either...

Practice › Codeforces Solutions › Codeforces Round 193 (Div. 2) ›

CF 332E - Binary Key

CF 332E - Binary Key Rating: 2400 Tags: dp, greedy, implementation Solve time: 1m 59s Verified: no Solution Problem Understanding We are given a container string p and a target message string s . The container is arbitrary, while the message contains the sequence we wish to extract. The extraction mechanism is governed by a binary key q of length k . The extraction proceeds sequentially through p and q...

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LeetCode 2789 - Largest Element in an Array after Merge Operations

LeetCode Problem 2789 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us an array of positive integers and allows a special merge operation between adjacent elements. We may choose an index i such that: nums[i] <= nums[i + 1] When this condition is satisfied, we merge the two elements by adding nums[i] into nums[i + 1] , then removing nums[i] from the array. In effect, the...

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LeetCode 2310 - Sum of Numbers With Units Digit K

LeetCode Problem 2310 Difficulty: 🟡 Medium Topics: Math, Dynamic Programming, Greedy, Enumeration Solution Problem Understanding This problem asks us to construct a set of positive integers such that: Every number in the set has a units digit equal to k . The sum of all numbers equals num . We want the smallest possible number of integers in the set. If it is impossible to create such a set, we...

Practice › Codeforces Solutions › Testing Round 8 ›

CF 328B - Sheldon and Ice Pieces

CF 328B - Sheldon and Ice Pieces Rating: 1500 Tags: greedy Solve time: 2m Verified: no Solution Here’s a automatically by

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LeetCode 3016 - Minimum Number of Pushes to Type Word II

LeetCode Problem 3016 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting, Counting Solution LeetCode 3016 - Minimum Number of Pushes to Type Word II Problem Understanding This problem asks us to redesign a telephone keypad so that typing a given word requires the fewest total key presses possible. A traditional telephone keypad contains keys 2 through 9 , giving us exactly 8 available keys . Each lowercase English letter...

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Coder-Strike 2014 - Round 2

Coder-Strike 2014 - Round 2 Type: Special | Problems: 5 | Verified: 4/5 | Rating range: 1200-2200 | Time: 9m 37s Problem Name Rating Tags Solve Time Verified A Data Recovery 1200 implementation 1m 42s ✓ B Spyke Chatting 1300 implementation 1m 48s ✗ C Jeopardy! 1400 greedy, math 2m 23s ✓ D 2048 2000 bitmasks, dp 2m 23s ✓ E Maze 2D 2200 data-structures, divide-and-conquer 1m 21s ✓

Practice › Codeforces Solutions › Codeforces Round 151 (Div. 2) ›

CF 246B - Increase and Decrease

CF 246B - Increase and Decrease Rating: 1300 Tags: greedy, math Solve time: 58s Verified: yes Solution Problem Understanding We have an array of integers, and we are allowed to pick two different elements and simultaneously increase one by 1 and decrease the other by 1. We can perform this operation as many times as we like. The task is to determine the largest number of array elements that can...

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LeetCode 3088 - Make String Anti-palindrome

LeetCode Problem 3088 Difficulty: 🔴 Hard Topics: String, Greedy, Sorting, Counting Sort Solution Problem Understanding We are given a string s of even length, and we may swap any two characters any number of times. Since unrestricted swapping allows us to rearrange the string arbitrarily, the real task is to determine whether some permutation of the characters can form an anti-palindrome. A string is an anti-palindrome if every character differs...

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LeetCode 2576 - Find the Maximum Number of Marked Indices

LeetCode Problem 2576 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding This problem asks us to maximize the number of indices in an array that can be "marked" using a specific operation. You are given an integer array nums and can repeatedly pick two different unmarked indices i and j such that 2 * nums[i] <= nums[j] . Once selected, both indices i and...

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VK Cup 2012 Qualification Round 1

VK Cup 2012 Qualification Round 1 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 800-1900 | Time: 7m 26s Problem Name Rating Tags Solve Time Verified A Next Round 800 *special, implementation 1m 29s ✓ B Taxi 1100 *special, greedy, implementation 1m 21s ✓ C Cd and pwd commands 1400 *special, data-structures, implementation 1m 45s ✓ D Ice Sculptures 1300 *special, brute-force, number-theory 1m 38s ✓ E...

Practice › Codeforces Solutions › Codeforces Round 244 (Div. 2) ›

CF 427E - Police Patrol

CF 427E - Police Patrol Rating: 2000 Tags: greedy, implementation, math, ternary search Solve time: 1m 54s Verified: yes Solution Problem Understanding All criminals stand on the x-axis, and we must choose one integer coordinate for the police station. The patrol car starts from the station, visits some criminals, brings them back to the station, then repeats until everyone is arrested. Each trip can carry at most m criminals. The...

Practice › Codeforces Solutions ›

Codeforces Round 113 (Div. 2)

Codeforces Round 113 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2500 | Time: 11m 49s Problem Name Rating Tags Solve Time Verified A Rank List 1100 binary-search, implementation, sortings 1m 31s ✓ B Polygons 2100 geometry, sortings 3m 7s ✓ C Median 1500 greedy, math, sortings 1m 37s ✓ D Shoe Store 2500 dp, graph-matchings, greedy 2m 34s ✓ E Tetrahedron 1500 dp,...

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LeetCode 2601 - Prime Subtraction Operation

LeetCode Problem 2601 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Number Theory Solution Problem Understanding The problem gives us an integer array nums and asks whether it is possible to transform the array into a strictly increasing sequence by performing a special operation. For any index i , we may choose that index at most once and subtract a prime number p from nums[i] , where p must...

Practice › Codeforces Solutions › Codeforces Round 142 (Div. 1) ›

CF 229D - Towers

CF 229D - Towers Rating: 2100 Tags: dp, greedy, two pointers Solve time: 2m 55s Verified: yes Solution Problem Understanding We are given a sequence of towers standing in a straight line, where the height of the tower at position i is h[i] . The goal is to make the sequence non-decreasing from left to right using a set of allowed operations. Each operation consists of picking a tower and...

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LeetCode 2708 - Maximum Strength of a Group

LeetCode Problem 2708 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Greedy, Bit Manipulation, Sorting, Enumeration Solution Problem Understanding The problem asks us to select a non-empty subset of integers from a given array nums such that the product of the numbers in the subset is maximized. Each number represents a student’s exam score, and the subset represents a group of students. The "strength" of a group is the product...

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Codeforces Round 204 (Div. 1)

Codeforces Round 204 (Div. 1) Type: Div. 1 | Problems: 2 | Verified: 1/2 | Rating range: 1800-2700 | Time: 4m 1s Problem Name Rating Tags Solve Time Verified A Jeff and Rounding 1800 dp, greedy, implementation 1m 37s ✗ D Jeff and Removing Periods 2700 data-structures 2m 24s ✓

Practice › Codeforces Solutions ›

Codeforces Round 154 (Div. 2)

Codeforces Round 154 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1100-2200 | Time: 7m 19s Problem Name Rating Tags Solve Time Verified A Boys and Girls 1100 greedy 1m 7s ✓ B Physics Practical 1400 binary-search, dp, sortings 3m 14s ✓ C Text Editor 1600 data-structures, dfs-and-similar, graphs 53s ✓ D Table with Letters - 2 2000 brute-force, two-pointers 1m 4s ✓ E...

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LeetCode 2383 - Minimum Hours of Training to Win a Competition

LeetCode Problem 2383 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem gives us two starting values, initialEnergy and initialExperience , which represent the player's stats before entering a sequence of competitions. We are also given two arrays, energy and experience , where each index corresponds to an opponent. To defeat opponent i , the player must satisfy two strict conditions at the moment the fight begins: Current...

Practice › Codeforces Solutions ›

Codeforces Round 193 (Div. 2)

Codeforces Round 193 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 0/2 | Rating range: 2200-2400 | Time: 9m Problem Name Rating Tags Solve Time Verified C Students' Revenge 2200 data-structures, greedy, sortings 7m 1s ✗ E Binary Key 2400 dp, greedy, implementation 1m 59s ✗

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LeetCode 2439 - Minimize Maximum of Array

LeetCode Problem 2439 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Greedy, Prefix Sum Solution Problem Understanding The problem gives a 0-indexed array nums of non-negative integers and allows a specific operation: choose an index i (where 1 <= i < n ) such that nums[i] > 0 , then decrease nums[i] by 1 and increase nums[i - 1] by 1. The task is to perform this operation any...

Practice › Codeforces Solutions › Codeforces Round 145 (Div. 1, ACM-ICPC Rules) ›

CF 240E - Road Repairs

CF 240E - Road Repairs Rating: 2800 Tags: dfs and similar, graphs, greedy Solve time: 1m 58s Verified: yes Solution Problem Understanding We have a directed graph of cities and roads. City 1 is the capital. Every road is either already usable or broken. A broken road may be repaired, after which it behaves like a normal directed edge. The government wants every city to become reachable from the capital....

Practice › Codeforces Solutions › Codeforces Round 106 (Div. 2) ›

CF 149A - Business trip

CF 149A - Business trip Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 33s Verified: yes Solution Problem Understanding Petya can decide in which months he waters the flower. Each month contributes a fixed amount of growth, and skipping a month contributes nothing. The goal is to reach at least k centimeters of total growth while using as few months as possible. The input gives the required growth k...

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LeetCode 2422 - Merge Operations to Turn Array Into a Palindrome

LeetCode Problem 2422 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy Solution Problem Understanding The problem asks us to transform a given array of positive integers into a palindrome using the minimum number of operations, where each operation consists of taking two adjacent elements and replacing them with their sum. A palindrome is an array that reads the same forward and backward, so for an array nums , we require...

Practice › Codeforces Solutions › Codeforces Round 160 (Div. 1) ›

CF 261A - Maxim and Discounts

CF 261A - Maxim and Discounts Rating: 1400 Tags: greedy, sortings Solve time: 3m 10s Verified: yes Solution Problem Understanding We are given a list of item prices and a collection of discount types. Each discount type describes how many items must be placed in a “paid group”. When Maxim uses a discount of size $q_i$, he chooses exactly $q_i$ items that he pays for, and in addition he may...

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LeetCode 2263 - Make Array Non-decreasing or Non-increasing

LeetCode Problem 2263 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to transform a given integer array nums into either a non-decreasing or a non-increasing array with the minimum number of operations. Each operation allows increasing or decreasing an element by exactly 1. A non-decreasing array is one in which every element is greater than or equal to the previous...

Practice › Codeforces Solutions › Croc Champ 2012 - Final ›

CF 183D - T-shirt

CF 183D - T-shirt Rating: 2700 Tags: dp, greedy, probabilities Solve time: 1m 15s Verified: yes Solution Problem Understanding We are tasked with distributing T-shirts to a line of engineers where each engineer has a probability distribution over which T-shirt size fits them. We know how many engineers, n , there are, and the total number of T-shirt sizes, m . Each engineer has exactly one size that fits them,...

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LeetCode 1881 - Maximum Value after Insertion

LeetCode Problem 1881 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding This problem asks us to insert a single digit x into a very large integer n , represented as a string, in a position that maximizes the resulting numerical value. The integer n can be either positive or negative. Since the number may be extremely large, up to 10^5 characters long, we cannot safely convert it to an...

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CF 161B - Discounts

CF 161B - Discounts Rating: 1700 Tags: constructive algorithms, greedy, sortings Solve time: 2m 13s Verified: yes Solution Problem Understanding We have a collection of items sold in a supermarket. Every item has a price and a type. Type 1 means the item is a stool, type 2 means it is a pencil. Polycarpus owns exactly k shopping carts, and every cart must contain at least one item. The store...

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LeetCode 2499 - Minimum Total Cost to Make Arrays Unequal

LeetCode Problem 2499 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding You are given two arrays, nums1 and nums2 , both of length n . You are allowed to perform operations only on nums1 . In a single operation, you may swap any two indices in nums1 , and the cost of that operation is the sum of the two indices involved in the swap. The...

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Codeforces Round 235 (Div. 2)

Codeforces Round 235 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 800-2000 | Time: 6m 53s Problem Name Rating Tags Solve Time Verified A Vanya and Cards 800 implementation, math 4m 10s ✗ B Sereja and Contests 1200 greedy, implementation, math 1m 24s ✓ D Roman and Numbers 2000 bitmasks, brute-force, combinatorics 1m 19s ✓

Practice › Codeforces Solutions › Codeforces Round 153 (Div. 1) ›

CF 251C - Number Transformation

CF 251C - Number Transformation Rating: 2000 Tags: dp, greedy, number theory Solve time: 14m 23s Verified: no Solution

Practice › Codeforces Solutions › Coder-Strike 2014 - Round 1 ›

CF 412A - Poster

CF 412A - Poster Rating: 900 Tags: greedy, implementation Solve time: 2m 3s Verified: no Solution Problem Understanding We are given a linear banner split into n fixed positions, and a cursor-like ladder that starts at position k. Each position corresponds to exactly one character of a target string, and we must eventually print that string left to right, one character per position. The only two things we are allowed...

Practice › Codeforces Solutions › Codeforces Round 180 (Div. 1) ›

CF 297B - Fish Weight

CF 297B - Fish Weight Rating: 1600 Tags: constructive algorithms, greedy Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given two people, Alice and Bob, each of whom has caught a collection of fish. Every fish belongs to one of k species, and species numbers are ordered so that species with a larger index are guaranteed to be at least as heavy as those with a smaller...

Practice › Codeforces Solutions › Codeforces Round 124 (Div. 1) ›

CF 196A - Lexicographically Maximum Subsequence

CF 196A - Lexicographically Maximum Subsequence Rating: 1100 Tags: greedy, strings Solve time: 1m 2s Verified: yes Solution Problem Understanding We are given a string composed of lowercase English letters, and our goal is to select a subsequence from it that is lexicographically the largest possible. A subsequence is formed by taking zero or more characters in order without reordering them. Lexicographical comparison is just dictionary order, so "bca" is...

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LeetCode 2271 - Maximum White Tiles Covered by a Carpet

LeetCode Problem 2271 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sliding Window, Sorting, Prefix Sum Solution That is a long-form reference guide request. To avoid truncation and keep the formatting exact, I will provide the complete solution guide for LeetCode 2271 in a single structured response. Problem Understanding The problem gives us a collection of disjoint white tile intervals and a carpet of fixed length. Each interval [li, ri]...

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Codeforces Round 116 (Div. 2, ACM-ICPC Rules)

Codeforces Round 116 (Div. 2, ACM-ICPC Rules) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1200-2300 | Time: 8m 3s Problem Name Rating Tags Solve Time Verified A Defragmentation 1800 implementation 1m 20s ✓ B Divisibility Rules 2300 math, number-theory 1m 50s ✓ C Letter 1400 dp 1m 46s ✓ D Name 1900 greedy, strings 1m 39s ✓ F Mathematical Analysis Rocks! 1200 constructive-algorithms, implementation, math...

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LeetCode 2745 - Construct the Longest New String

LeetCode Problem 2745 Difficulty: 🟡 Medium Topics: Math, Dynamic Programming, Greedy, Brainteaser Solution LeetCode 2745 - Construct the Longest New String Problem Understanding The problem gives us three types of fixed two-character strings: "AA" appears x times "BB" appears y times "AB" appears z times We may choose any subset of these strings and concatenate them in any order. The goal is to build the longest possible resulting string while...

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LeetCode 1962 - Remove Stones to Minimize the Total

LeetCode Problem 1962 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array called piles , where each element represents the number of stones in a pile. We are also given an integer k , representing the exact number of operations we must perform. In one operation, we choose a pile and remove floor(pile / 2) stones from it. Since we remove...

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LeetCode 3205 - Maximum Array Hopping Score I

LeetCode Problem 3205 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to calculate the maximum score achievable by hopping through an array from the first element to the last. You start at index 0 , and at each step, you can jump to any subsequent index j > i . When you jump, you accumulate a score of (j -...

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LeetCode 2279 - Maximum Bags With Full Capacity of Rocks

LeetCode Problem 2279 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem presents n bags, each with a defined maximum capacity and a current number of rocks. The input consists of two arrays: capacity and rocks , where capacity[i] is the maximum number of rocks bag i can hold, and rocks[i] is how many rocks are currently in that bag. Additionally, you are given an integer additionalRocks...

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LeetCode 2170 - Minimum Operations to Make the Array Alternating

LeetCode Problem 2170 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding The problem requires transforming a given integer array nums into an alternating array with the minimum number of operations. An array is alternating if elements at even indices repeat every two steps ( nums[i] == nums[i-2] for i >= 2 ) and elements at odd indices differ from their previous element ( nums[i] != nums[i-1]...

Practice › Codeforces Solutions › Codeforces Round 127 (Div. 2) ›

CF 202A - LLPS

CF 202A - LLPS Rating: 800 Tags: binary search, bitmasks, brute force, greedy, implementation, strings Solve time: 1m 6s Verified: yes Solution Problem Understanding We are given a lowercase string and must choose some characters, in order, to form a subsequence that is both a palindrome and lexicographically as large as possible. A subsequence does not need to stay contiguous. We may skip characters, but the remaining characters must keep...

Practice › Codeforces Solutions › Codeforces Round 133 (Div. 2) ›

CF 216C - Hiring Staff

CF 216C - Hiring Staff Rating: 1800 Tags: greedy Solve time: 2m 5s Verified: no Solution Problem Understanding Each employee follows a rigid repeating schedule. Once hired on day x , the employee works for n consecutive days, then rests for m consecutive days, then repeats forever. So the cycle length is n + m , and inside each cycle the employee is active for the first n days. The...

Practice › Codeforces Solutions › Codeforces Round 143 (Div. 2) ›

CF 231A - Team

CF 231A - Team Rating: 800 Tags: brute force, greedy Solve time: 56s Verified: yes Solution Problem Understanding We are asked to determine how many problems a team of three friends will attempt during a programming contest. Each friend independently has confidence about each problem, represented as a binary value: 1 if the friend is confident they know the solution, 0 otherwise. A problem will be solved only if at...

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Codeforces Beta Round 99 (Div. 1)

Codeforces Beta Round 99 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1600-2900 | Time: 9m 53s Problem Name Rating Tags Solve Time Verified A Literature Lesson 1600 implementation 2m ✓ B Digits Permutations 1900 greedy 2m 29s ✗ C Mushroom Gnomes - 2 2200 binary-search, data-structures, probabilities 2m ✓ D World of Darkraft 2500 dp, games 2m 6s ✓ E Hellish Constraints 2900...

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Codeforces Round 111 (Div. 2)

Codeforces Round 111 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2400 | Time: 8m 5s Problem Name Rating Tags Solve Time Verified A Twins 900 greedy, sortings 1m 15s ✓ B Unlucky Ticket 1100 greedy, sortings 1m 29s ✓ C Find Pair 1700 implementation, math, sortings 1m 47s ✓ D Edges in MST 2300 dfs-and-similar, dsu, graphs 1m 21s ✓ E Buses and...

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LeetCode 2599 - Make the Prefix Sum Non-negative

LeetCode Problem 2599 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to manipulate an array of integers, nums , so that its prefix sums are never negative. A prefix sum at index i is simply the sum of all elements from the start of the array up to i . The only operation allowed is to take any element in nums and...

Practice › Codeforces Solutions › Codeforces Round 160 (Div. 2) ›

CF 262B - Roma and Changing Signs

CF 262B - Roma and Changing Signs Rating: 1200 Tags: greedy Solve time: 7m 26s Verified: no Solution

Practice › Codeforces Solutions › VK Cup 2012 Round 1 ›

CF 161A - Dress'em in Vests!

CF 161A - Dress'em in Vests! Rating: 1300 Tags: binary search, brute force, greedy, two pointers Solve time: 1m 15s Verified: yes Solution Problem Understanding We are tasked with equipping as many soldiers as possible with bulletproof vests. Each soldier has a preferred vest size, but they are willing to tolerate deviations within a given range. Specifically, the i-th soldier can wear any vest with a size between a[i] -...

Practice › Codeforces Solutions › Codeforces Round 168 (Div. 1) ›

CF 274B - Zero Tree

CF 274B - Zero Tree Rating: 1800 Tags: dfs and similar, dp, greedy, trees Solve time: 3m 28s Verified: yes Solution Problem Understanding This problem asks whether a matrix returns to its original form after repeatedly applying cyclic row shifts. The matrix has m rows and n columns. Every operation affects all rows simultaneously, but the direction depends on the row index. Rows with even indices, such as 0 ,...

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LeetCode 2734 - Lexicographically Smallest String After Substring Operation

LeetCode Problem 2734 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding The problem gives us a lowercase English string s . We must perform exactly one operation: Choose any non-empty substring. Replace every character in that substring with the previous character in the alphabet. 'b' becomes 'a' 'c' becomes 'b' 'a' wraps around and becomes 'z' After performing exactly one such operation, we must return the lexicographically smallest possible...

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Codeforces Round 117 (Div. 2)

Codeforces Round 117 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2200 | Time: 11m 48s Problem Name Rating Tags Solve Time Verified A Battlefield 2200 geometry, graphs, implementation 3m 47s ✓ B Vasya's Calendar 1000 implementation 3m 18s ✗ C Optimal Sum 2000 data-structures, greedy 1m 50s ✓ D Common Divisors 1400 brute-force, hashing, implementation 1m 36s ✓ E Wooden Fence 1800 dp...

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LeetCode 2136 - Earliest Possible Day of Full Bloom

LeetCode Problem 2136 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem presents a scenario where we have n flower seeds, each of which requires two phases to bloom: a planting phase and a growth phase. Each seed i takes plantTime[i] full days to plant, which can be spread across non-consecutive days. After planting, the seed requires growTime[i] full days to grow, and only after this period...

Practice › Codeforces Solutions › Codeforces Round 190 (Div. 1) ›

CF 321C - Ciel the Commander

CF 321C - Ciel the Commander Rating: 2100 Tags: constructive algorithms, dfs and similar, divide and conquer, greedy, trees Solve time: 3m 39s Verified: yes Solution Problem Understanding We are given a tree with n cities connected by n-1 roads. Each city must be assigned an officer with a rank from 'A' (highest) to 'Z' (lowest). The constraint is that if two cities share the same officer rank, the path...

Practice › Codeforces Solutions › Codeforces Round 168 (Div. 1) ›

CF 274A - k-Multiple Free Set

CF 274A - k-Multiple Free Set Rating: 1500 Tags: binary search, greedy, sortings Solve time: 1m 14s Verified: yes Solution Problem Understanding We are asked to find the largest subset of a given set of positive integers such that no element in the subset is exactly k times another element in the subset. Formally, for a given integer k , we must ensure that for any two numbers x and...

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LeetCode 3075 - Maximize Happiness of Selected Children

LeetCode Problem 3075 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us an array happiness representing the happiness values of n children standing in a queue and asks us to select exactly k children to maximize the sum of their happiness. The twist is that each time we select a child, all unselected children have their happiness decreased by 1, but their happiness cannot go...

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LeetCode 2131 - Longest Palindrome by Concatenating Two Letter Words

LeetCode Problem 2131 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Greedy, Counting Solution Problem Understanding This problem asks us to construct the longest possible palindrome using a list of two-letter words. Each word can be used at most once, and the order of concatenation can be chosen freely. A palindrome reads the same forwards and backwards, which means that for a word pair to appear symmetrically around the center,...

Practice › Codeforces Solutions › VK Cup 2012 Finals, Practice Session ›

CF 209C - Trails and Glades

CF 209C - Trails and Glades Rating: 2400 Tags: constructive algorithms, dsu, graphs, greedy Solve time: 5m 3s Verified: yes Solution Problem Understanding The park is an undirected multigraph. Glades are vertices, trails are edges. Self-loops are allowed, and multiple edges between the same pair of vertices are also allowed. Vasya wants to start at vertex 1, traverse every edge exactly once, and return to vertex 1. This is exactly...

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LeetCode 2663 - Lexicographically Smallest Beautiful String

LeetCode Problem 2663 Difficulty: 🔴 Hard Topics: String, Greedy Solution Problem Understanding The problem requires generating the lexicographically smallest beautiful string that is strictly larger than a given beautiful string s . A string is beautiful if it uses only the first k letters of the English alphabet and contains no palindromic substring of length 2 or more. Essentially, no two consecutive letters can be the same, and no three...

Practice › Codeforces Solutions ›

VK Cup 2012 Round 3 (Unofficial Div. 2 Edition)

VK Cup 2012 Round 3 (Unofficial Div. 2 Edition) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 1100-1800 | Time: 6m 56s Problem Name Rating Tags Solve Time Verified A Problem About Equation 1100 math 1m 33s ✓ B File List 1400 dp, greedy, implementation 3m 40s ✓ C Range Increments 1800 data-structures, greedy 1m 43s ✓

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CF 436E - Cardboard Box

CF 436E - Cardboard Box Rating: 2600 Tags: data structures, greedy Solve time: 1m 21s Verified: no Solution Problem Understanding We are given a set of levels in a game, each with two possible completion times. Completing a level for one star takes a[i] time, and completing it for two stars takes b[i] time, with a[i] < b[i] . We start with zero stars, and the goal is to accumulate...

Practice › Codeforces Solutions › Croc Champ 2013 - Round 2 ›

CF 293A - Weird Game

CF 293A - Weird Game Rating: 1500 Tags: games, greedy Solve time: 53s Verified: yes Solution Problem Understanding We are asked to analyze a turn-based game played by two players, Yaroslav and Andrey, each starting with a binary string of length 2·n. On their turn, a player chooses an index in the string that hasn’t been picked yet and writes down the corresponding character on their paper. Yaroslav always moves...

Practice › Codeforces Solutions › Codeforces Round 122 (Div. 1) ›

CF 193C - Hamming Distance

CF 193C - Hamming Distance Rating: 2400 Tags: constructive algorithms, greedy, math, matrices Solve time: 2m 31s Verified: no Solution Problem Understanding We are given the six pairwise Hamming distances between four unknown binary strings. Every string contains only 'a' and 'b' , and all four strings must have the same length. The task is not to recover the original strings. We only need to construct any four strings whose...

Practice › Codeforces Solutions › Codeforces Round 173 (Div. 2) ›

CF 282B - Painting Eggs

CF 282B - Painting Eggs Rating: 1500 Tags: greedy, math Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given a list of eggs, each of which can be painted by either of two children, A or G. Each child quotes a price for painting each egg, and these prices for a single egg always sum to exactly 1000. Uncle J. wants to assign each egg to exactly...

Practice › Codeforces Solutions › Codeforces Round 162 (Div. 2) ›

CF 265B - Roadside Trees (Simplified Edition)

CF 265B - Roadside Trees (Simplified Edition) Rating: 1000 Tags: greedy, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We have a sequence of trees along a straight street. Each tree has a certain height, and on top of each tree is a nut that Squirrel Liss wants to eat. Liss starts at the base of the first tree. She can move up or down by one unit...

Practice › Codeforces Solutions › Codeforces Round 131 (Div. 2) ›

CF 214B - Hometask

CF 214B - Hometask Rating: 1600 Tags: brute force, constructive algorithms, greedy, math Solve time: 2m 49s Verified: yes Solution Problem Understanding We are given a multiset of digits and asked to construct the largest integer from some or all of them such that the resulting number is divisible by 2, 3, and 5 simultaneously. Because a number divisible by 2, 3, and 5 is divisible by 30, the task...

Practice › Codeforces Solutions › Codeforces Round #FF (Div. 2) ›

CF 447B - DZY Loves Strings

CF 447B - DZY Loves Strings Rating: 1000 Tags: greedy, implementation Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a string made of lowercase letters and a way to assign a numerical weight to each letter. The value of a full string is computed by summing, over all positions, the product of the position index (starting from 1) and the weight of the character at that...

Practice › Codeforces Solutions › Codeforces Round 203 (Div. 2) ›

CF 350A - TL

CF 350A - TL Rating: 1200 Tags: brute force, greedy, implementation Solve time: 6m 57s Verified: no Solution

Practice › Codeforces Solutions › Codeforces Round 236 (Div. 2) ›

CF 402D - Upgrading Array

CF 402D - Upgrading Array Rating: 1800 Tags: dp, greedy, math, number theory Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given an array of positive integers and a set of "bad" prime numbers. Every other prime not in the bad set is implicitly "good." Each number in the array contributes to a total "beauty" score determined by its prime factorization. The contribution of a number is...

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LeetCode 2829 - Determine the Minimum Sum of a k-avoiding Array

LeetCode Problem 2829 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to construct an array of n distinct positive integers such that no two elements in the array sum to a given integer k . This type of array is called k-avoiding . Among all possible k-avoiding arrays of length n , we are asked to find the minimum possible sum of its elements. The...

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LeetCode 2967 - Minimum Cost to Make Array Equalindromic

LeetCode Problem 2967 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Sorting Solution LeetCode 2967 - Minimum Cost to Make Array Equalindromic Problem Understanding We are given an integer array nums . We may repeatedly choose any element and replace it with any positive integer x . Replacing a value nums[i] with x costs |nums[i] - x| . The goal is to transform the array so that every element...

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LeetCode 2971 - Find Polygon With the Largest Perimeter

LeetCode Problem 2971 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Prefix Sum Solution LeetCode 2971 - Find Polygon With the Largest Perimeter Problem Understanding The problem gives us an array nums containing positive integers. Each integer represents a potential side length that we may use when constructing a polygon. A polygon must have at least three sides. The key geometric property we are given is that if the side lengths...

Practice › Codeforces Solutions › Codeforces Round 151 (Div. 2) ›

CF 246A - Buggy Sorting

CF 246A - Buggy Sorting Rating: 900 Tags: constructive algorithms, greedy, sortings Solve time: 1m 8s Verified: yes Solution Problem Understanding We are given only a single integer $n$, and we must construct an array of length $n$ that either breaks a very specific sorting procedure or prove that no such array exists. The procedure itself is a double loop that repeatedly scans adjacent pairs in a prefix-like manner and...

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LeetCode 2244 - Minimum Rounds to Complete All Tasks

LeetCode Problem 2244 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Here is a complete, detailed technical solution guide for LeetCode 2244 - Minimum Rounds to Complete All Tasks following your formatting and content requirements. Problem Understanding The problem provides a 0-indexed array tasks , where each element represents a task's difficulty level. Each round, you are allowed to complete exactly 2 or 3 tasks of the same...

Practice › Codeforces Solutions › Codeforces Round 117 (Div. 2) ›

CF 182C - Optimal Sum

CF 182C - Optimal Sum Rating: 2000 Tags: data structures, greedy Solve time: 1m 50s Verified: yes Solution Problem Understanding We have an array and a fixed window length len . For every subarray of length len , we compute its sum and then take the absolute value. The "optimal sum" of the whole array is the maximum absolute subarray sum among all windows of that fixed length. Before evaluating...

Practice › Codeforces Solutions › Codeforces Round 199 (Div. 2) ›

CF 342A - Xenia and Divisors

CF 342A - Xenia and Divisors Rating: 1200 Tags: greedy, implementation Solve time: 6m 2s Verified: no Solution Problem Understanding We are given a sequence of positive integers, all between 1 and 7, whose length is divisible by three. The task is to split this sequence into triplets so that within each triplet the numbers are strictly increasing and each number divides the next. Each integer must appear in exactly...

Practice › Codeforces Solutions › Codeforces Round 159 (Div. 2) ›

CF 257B - Playing Cubes

CF 257B - Playing Cubes Rating: 1300 Tags: games, greedy, implementation Solve time: 1m 23s Verified: yes Solution Problem Understanding We are asked to simulate a game between two players arranging colored cubes in a line. Petya wants to maximize the number of consecutive cubes of the same color, while Vasya wants to maximize the number of consecutive cubes of different colors. Petya moves first, and the total number of...

Practice › Codeforces Solutions ›

Codeforces Round 133 (Div. 2)

Codeforces Round 133 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1200-2000 | Time: 7m 31s Problem Name Rating Tags Solve Time Verified A Tiling with Hexagons 1200 implementation, math 56s ✓ B Forming Teams 1700 dfs-and-similar, implementation 1m 27s ✓ C Hiring Staff 1800 greedy 2m 5s ✗ D Spider's Web 1700 binary-search, sortings, two-pointers 1m 26s ✗ E Martian Luck 2000 math,...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1969 - Minimum Non-Zero Product of the Array Elements

LeetCode Problem 1969 Difficulty: 🟡 Medium Topics: Math, Greedy, Recursion Solution LeetCode 1969, Minimum Non-Zero Product of the Array Elements Problem Understanding The problem gives us an integer p and defines an array containing every number from 1 to 2^p - 1 . Each number is represented in binary using exactly p bits. We are allowed to repeatedly perform a special operation. In one operation, we choose two numbers and...

Practice › Codeforces Solutions ›

Codeforces Round 179 (Div. 2)

Codeforces Round 179 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1100-1100 | Time: 57s Problem Name Rating Tags Solve Time Verified A Yaroslav and Permutations 1100 greedy, math 57s ✓

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LeetCode 2405 - Optimal Partition of String

LeetCode Problem 2405 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy Solution Problem Understanding The problem asks us to divide a given string s into the minimum number of substrings such that every substring contains only unique characters . In other words, within a single substring, no character may appear more than once. We are given a string of lowercase English letters and must split it into contiguous pieces. Every...

Practice › Codeforces Solutions ›

Codeforces Round 144 (Div. 1)

Codeforces Round 144 (Div. 1) Type: Div. 1 | Problems: 4 | Verified: 2/4 | Rating range: 1600-2900 | Time: 17m 15s Problem Name Rating Tags Solve Time Verified A Cycles 1600 binary-search, constructive-algorithms, graphs 3m 45s ✓ B Table 1900 bitmasks, combinatorics, dp 8m 46s ✗ C Doe Graphs 2600 constructive-algorithms, divide-and-conquer, dp 2m 23s ✓ D Fence 2900 binary-search, data-structures, string-suffix-structures 2m 21s ✗

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2900 - Longest Unequal Adjacent Groups Subsequence I

LeetCode Problem 2900 Difficulty: 🟢 Easy Topics: Array, String, Dynamic Programming, Greedy Solution LeetCode 2900 - Longest Unequal Adjacent Groups Subsequence I Problem Understanding We are given two arrays of the same length: words[i] is a string. groups[i] is either 0 or 1 . We want to select a subsequence of words . A subsequence preserves the original order of elements, but we may skip any number of elements. The...

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Codeforces Round 152 (Div. 2)

Codeforces Round 152 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2600 | Time: 11m 52s Problem Name Rating Tags Solve Time Verified A Cupboards 800 implementation 1m 34s ✓ B Chilly Willy 1400 math, number-theory 2m 53s ✓ C Robo-Footballer 2000 binary-search, geometry 2m ✗ D Sweets for Everyone! 2300 binary-search, greedy, implementation 3m 8s ✓ E Piglet's Birthday 2600 dp, math, probabilities...

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LeetCode 3397 - Maximum Number of Distinct Elements After Operations

LeetCode Problem 3397 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to maximize the number of distinct elements in an integer array nums by performing a limited set of operations. Each element can be modified at most once by adding an integer in the range [-k, k] . The goal is to determine the largest possible count of unique numbers after applying these operations...

Practice › Codeforces Solutions › Codeforces Beta Round 99 (Div. 1) ›

CF 138B - Digits Permutations

CF 138B - Digits Permutations Rating: 1900 Tags: greedy Solve time: 2m 29s Verified: no Solution Problem Understanding We are given a decimal number as a string. We may independently permute its digits twice, producing two new numbers that contain exactly the same multiset of digits as the original number. Leading zeroes are allowed after permutation. Our goal is to arrange the digits so that the sum of the two...

Practice › Codeforces Solutions › Codeforces Round 102 (Div. 1) ›

CF 142B - Help General

CF 142B - Help General Rating: 1800 Tags: constructive algorithms, greedy, implementation Solve time: 1m 38s Verified: yes Solution Problem Understanding We have an n × m chessboard-like grid, and we want to place as many soldiers as possible. Two soldiers conflict if the squared Euclidean distance between their cells is exactly 5 . The only integer pairs whose squared distance equals 5 are (1, 2) and (2, 1) up...

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Codeforces Round 140 (Div. 1)

Codeforces Round 140 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1400-2900 | Time: 14m 33s Problem Name Rating Tags Solve Time Verified A Flying Saucer Segments 1400 math 5m 43s ✓ B Naughty Stone Piles 1900 greedy 2m 22s ✓ C Anniversary 2400 data-structures, implementation, math 2m 19s ✓ D The table 2100 constructive-algorithms, greedy 2m 58s ✗ E Noble Knight's Path 2900...

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LeetCode 2132 - Stamping the Grid

LeetCode Problem 2132 Difficulty: 🔴 Hard Topics: Array, Greedy, Matrix, Prefix Sum Solution Problem Understanding In this problem, we are given a binary matrix called grid . Every cell contains either: 0 , meaning the cell is empty 1 , meaning the cell is blocked or occupied We are also given a rectangular stamp with dimensions: stampHeight stampWidth The goal is to determine whether it is possible to place any...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2551 - Put Marbles in Bags

LeetCode Problem 2551 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem asks us to distribute weights.length marbles into k contiguous bags, where the cost of a bag is defined as the sum of the first and last marble in that bag. We are to calculate the difference between the maximum and minimum possible total scores across all valid distributions. The input weights is...

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LeetCode 2384 - Largest Palindromic Number

LeetCode Problem 2384 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Counting Solution Problem Understanding The problem asks us to form the largest palindromic integer using the digits from a given string num . A palindrome is a number that reads the same forwards and backwards, like 121 or 7449447 . The input string num consists only of digits ( 0 to 9 ) and may include repeated digits. We...

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LeetCode 3189 - Minimum Moves to Get a Peaceful Board

LeetCode Problem 3189 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Counting Sort Solution Problem Understanding In this problem, we are given the positions of n rooks placed on an n x n chessboard. Each rook is represented as a pair [xi, yi] , where xi is the row index and yi is the column index. A peaceful board is defined as a board where: Every row contains exactly one rook...

Practice › Codeforces Solutions › CROC-MBTU 2012, Final Round (Online version, Div. 2) ›

CF 250C - Movie Critics

CF 250C - Movie Critics Rating: 1600 Tags: greedy Solve time: 3m 12s Verified: no Solution Problem Understanding We are given a sequence of movie genres scheduled over n days, with exactly one movie per day. There are k genres, and each genre appears at least once. Valentine, a critic, experiences stress whenever the genre of consecutive movies he watches changes. He plans to skip all movies of a single...

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LeetCode 2457 - Minimum Addition to Make Integer Beautiful

LeetCode Problem 2457 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to transform a given integer n into a beautiful integer by adding the smallest non-negative integer x . An integer is defined as beautiful if the sum of its digits is less than or equal to a given target . The input consists of two numbers: n (the original number) and target (the maximum...

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LeetCode 2171 - Removing Minimum Number of Magic Beans

LeetCode Problem 2171 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Enumeration, Prefix Sum Solution Problem Understanding The problem asks us to remove beans from bags in such a way that all non-empty bags have the same number of beans while minimizing the total number of beans removed. Each element in the input array beans represents a bag with a positive number of beans. We are allowed to remove any number...

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LeetCode 3170 - Lexicographically Minimum String After Removing Stars

LeetCode Problem 3170 Difficulty: 🟡 Medium Topics: Hash Table, String, Stack, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to transform a string s that may contain the '*' character into a lexicographically smallest string by repeatedly applying a deletion operation. Specifically, for each '*' in the string, we must remove it along with the smallest non- '*' character to its left . If there are multiple...

Practice › Codeforces Solutions › Codeforces Round 140 (Div. 1) ›

CF 226D - The table

CF 226D - The table Rating: 2100 Tags: constructive algorithms, greedy Solve time: 2m 58s Verified: no Solution Problem Understanding We are given a rectangular table of integers with $n$ rows and $m$ columns. Each cell contains a number that could be positive, negative, or zero. Harry can perform two types of operations: flip the sign of all numbers in a row or flip the sign of all numbers in...

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LeetCode 2091 - Removing Minimum and Maximum From Array

LeetCode Problem 2091 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us a 0-indexed array of distinct integers. Among these integers, exactly one value is the smallest element in the array, and exactly one value is the largest element in the array. The task is to remove both of these elements using the fewest deletions possible. A deletion operation is very restricted. We are only allowed...

Practice › Codeforces Solutions › Codeforces Round 114 (Div. 1) ›

CF 167D - Wizards and Roads

CF 167D - Wizards and Roads Rating: 3000 Tags: data structures, divide and conquer, graph matchings, graphs, greedy Solve time: 2m 8s Verified: yes Solution Problem Understanding We are given a set of cities on the plane. Every city has a unique x coordinate and a unique y coordinate. The first k cities are given explicitly, and the remaining cities are generated by two linear recurrences. For every query interval...

Practice › Codeforces Solutions › Codeforces Round 165 (Div. 1) ›

CF 269C - Flawed Flow

CF 269C - Flawed Flow Rating: 2100 Tags: constructive algorithms, flows, graphs, greedy Solve time: 2m Verified: yes Solution Problem Understanding We are given an undirected graph where every edge already has a flow amount attached to it. The graph is supposed to represent a valid maximum flow from vertex 1 to vertex n , but the directions of the edges were lost. Our task is to recover directions for...

Practice › Codeforces Solutions › Codeforces Round 148 (Div. 1) ›

CF 238C - World Eater Brothers

CF 238C - World Eater Brothers Rating: 2100 Tags: dfs and similar, dp, greedy, trees Solve time: 2m 5s Verified: yes Solution Problem Understanding We are given a world of n countries connected by n-1 directed roads. Ignoring the direction of these roads, the countries form a tree. Each brother wants to establish rule in some country and can control every country reachable via directed roads. The problem asks for...

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LeetCode 3218 - Minimum Cost for Cutting Cake I

LeetCode Problem 3218 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem gives us an m x n rectangular cake and asks us to cut it into individual 1 x 1 pieces. We are allowed to cut along predefined horizontal and vertical lines. Each line has a fixed cost associated with it. The important detail is that the same cut may need to...

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LeetCode 3221 - Maximum Array Hopping Score II

LeetCode Problem 3221 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Monotonic Stack Solution LeetCode 3221 - Maximum Array Hopping Score II Problem Understanding The problem gives us an integer array nums , where each position represents a possible location we can stand on. We always begin at index 0 , and we must eventually reach the last index of the array. From any index i , we are allowed to...

Practice › Codeforces Solutions › Codeforces Round 163 (Div. 2) ›

CF 266C - Below the Diagonal

CF 266C - Below the Diagonal Rating: 2100 Tags: constructive algorithms, greedy, math Solve time: 2m 17s Verified: no Solution Problem Understanding We are given an $n \times n$ binary matrix with exactly $n-1$ ones. We may swap any two rows or any two columns. The goal is to rearrange the matrix so that every one ends up strictly below the main diagonal. In other words, if a one is...

Practice › Codeforces Solutions › CROC-MBTU 2012, Final Round (Online version, Div. 2) ›

CF 250A - Paper Work

CF 250A - Paper Work Rating: 1000 Tags: greedy Solve time: 3m 9s Verified: no Solution Problem Understanding Polycarpus needs to organize daily profit reports into folders, where each folder contains consecutive days. The key restriction is that a folder cannot contain three or more days with negative profit, because the boss cannot tolerate more than two loss days per folder. The goal is to minimize the total number of...

Practice › Codeforces Solutions › Codeforces Round 206 (Div. 1) ›

CF 354A - Vasya and Robot

CF 354A - Vasya and Robot Rating: 1500 Tags: brute force, greedy, math Solve time: 2m 39s Verified: yes Solution Problem Understanding Vasya has a line of items, each with a specific weight, and he wants a robot to pick all of them using its two arms. The left arm can take the leftmost item and the right arm can take the rightmost item. Each pick costs energy proportional to...

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LeetCode 3291 - Minimum Number of Valid Strings to Form Target I

LeetCode Problem 3291 Difficulty: 🟡 Medium Topics: Array, String, Binary Search, Dynamic Programming, Greedy, Trie, Segment Tree, Rolling Hash, String Matching, Hash Function Solution Problem Understanding We are given a list of strings called words and another string called target . The task is to construct target by concatenating several smaller strings, where each smaller string must be a prefix of at least one word in words . A prefix...

Practice › Codeforces Solutions › Codeforces Round 200 (Div. 1) ›

CF 343C - Read Time

CF 343C - Read Time Rating: 1900 Tags: binary search, greedy, two pointers Solve time: 16m 21s Verified: no Solution Problem Understanding We have a set of reading heads positioned on an infinitely long tape of tracks. Each head starts at a distinct track, and it can move left, right, or stay put once per second. We are given another set of target tracks that must be read, and the...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1864 - Minimum Number of Swaps to Make the Binary String Alternating

LeetCode Problem 1864 Difficulty: 🟡 Medium Topics: String, Greedy Solution LeetCode 1864 - Minimum Number of Swaps to Make the Binary String Alternating Problem Understanding The problem gives us a binary string s that contains only '0' and '1' . We are allowed to swap any two characters in the string, not necessarily adjacent ones. Our goal is to transform the string into an alternating binary string using the minimum...

Practice › Codeforces Solutions › Croc Champ 2013 - Finals (online version, Div. 1) ›

CF 309C - Memory for Arrays

CF 309C - Memory for Arrays Rating: 1900 Tags: binary search, bitmasks, greedy Solve time: 3m 39s Verified: yes Solution Problem Understanding The problem models a simplified memory allocation scenario. We have a computer’s RAM represented as a sequence of cells. Some of these cells are already occupied, and the remaining empty consecutive sequences form memory clusters. Each cluster is described by its size in cells. Separately, a program wants...

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Codeforces Round 236 (Div. 2)

Codeforces Round 236 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 1/4 | Rating range: 1100-2200 | Time: 11m 10s Problem Name Rating Tags Solve Time Verified A Nuts 1100 greedy, math 4m 11s ✗ B Trees in a Row 1400 brute-force, implementation 2m 19s ✗ D Upgrading Array 1800 dp, greedy, math 1m 3s ✓ E Strictly Positive Matrix 2200 graphs, math 3m 37s ✗

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CF 213A - Game

CF 213A - Game Rating: 1700 Tags: dfs and similar, greedy Solve time: 52s Verified: yes Solution Problem Understanding We are given a game split into n parts. Each part must be completed on a specific computer, and some parts depend on others, forming a dependency graph without cycles. Rubik can start at any computer and spends exactly one hour to complete a part. Moving between computers has asymmetric costs:...

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LeetCode 2406 - Divide Intervals Into Minimum Number of Groups

LeetCode Problem 2406 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum Solution Problem Understanding The problem gives us a list of inclusive intervals, where each interval is represented as [left, right] . We must divide all intervals into groups such that no two intervals inside the same group intersect. The important detail is that the intervals are inclusive. This means two intervals overlap even...

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LeetCode 1903 - Largest Odd Number in String

LeetCode Problem 1903 Difficulty: 🟢 Easy Topics: Math, String, Greedy Solution Problem Understanding The problem asks us to find the largest-valued odd integer substring from a given string num that represents a large integer. Here, a substring is any contiguous sequence of characters in num . We must return the substring itself as a string, or an empty string if no odd number exists in num . For example, if...

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CF 245E - Mishap in Club

CF 245E - Mishap in Club Rating: 1400 Tags: greedy, implementation Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given a chronological log of a single night in a club. Every character in the input string represents one event: a “+” means someone entered the club, and a “-” means someone left. We do not know how many people were initially inside before the log started, and...

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LeetCode 1946 - Largest Number After Mutating Substring

LeetCode Problem 1946 Difficulty: 🟡 Medium Topics: Array, String, Greedy Solution Problem Understanding This problem asks us to construct the lexicographically largest possible numeric string after optionally applying a single transformation operation on one contiguous substring of the input string num . Each digit in num can be transformed independently using a fixed mapping array change , where change[d] defines the replacement digit for digit d . We are allowed...

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CF 440B - Balancer

CF 440B - Balancer Rating: 1600 Tags: greedy, implementation Solve time: 1m 3s Verified: yes Solution Problem Understanding We are given a row of matchboxes, each containing some number of matches. The total number of matches is divisible by the number of boxes, so there exists a target configuration where every box ends up holding exactly the same number. The only allowed operation is moving a single match from one...

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CF 417D - Cunning Gena

CF 417D - Cunning Gena Rating: 1900 Tags: bitmasks, dp, greedy, sortings Solve time: 34s Verified: no Solution Problem Understanding Gena has a set of problems, and a group of friends who can each solve some subset of them. If Gena hires a friend, that friend will solve all problems they are capable of solving, covering multiple problems at once. Each friend has two independent costs: a fixed monetary payment...

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CF 306B - Optimizer

CF 306B - Optimizer Rating: 2100 Tags: data structures, greedy, sortings Solve time: 1m 26s Verified: yes Solution Problem Understanding We are given a linear memory array of size n and a set of m instructions, each of which sets a contiguous block of memory to the value 13. The instructions are indexed in the input order. Some instructions may overlap, fully or partially, with others. Our task is to...

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LeetCode 2071 - Maximum Number of Tasks You Can Assign

LeetCode Problem 2071 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Greedy, Queue, Sorting, Monotonic Queue Solution Problem Understanding This problem asks us to maximize the number of tasks that can be completed using a group of workers, where each worker can perform at most one task. Each task has a required strength value, and each worker has a current strength value. A worker can complete a task if...

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ABBYY Cup 3.0

ABBYY Cup 3.0 Type: Special | Problems: 12 | Verified: 6/12 | Rating range: 1100-2400 | Time: 30m 35s Problem Name Rating Tags Solve Time Verified A1 Special Task 1100 greedy 1m 30s ✗ B1 EKG 1500 brute-force, dfs-and-similar 3m 27s ✗ B2 EKG 1600 dfs-and-similar, dp 3m 21s ✗ C1 Tidying Up 2200 flows 1m 56s ✓ C2 Tidying Up 2300 flows, graph-matchings 3m 19s ✓ D2 PE Lesson...

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Codeforces Round 143 (Div. 2)

Codeforces Round 143 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 800-1600 | Time: 5m 32s Problem Name Rating Tags Solve Time Verified A Team 800 brute-force, greedy 56s ✓ B Magic, Wizardry and Wonders 1500 constructive-algorithms, greedy 1m 38s ✓ C To Add or Not to Add 1600 binary-search, sortings, two-pointers 2m 58s ✓

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Codeforces Round 203 (Div. 2)

Codeforces Round 203 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 1/4 | Rating range: 1200-2200 | Time: 17m 31s Problem Name Rating Tags Solve Time Verified A TL 1200 brute-force, greedy, implementation 6m 57s ✗ B Resort 1500 graphs 4m 28s ✗ C Bombs 1600 greedy, implementation, sortings 3m 48s ✓ E Wrong Floyd 2200 brute-force, constructive-algorithms, dfs-and-similar 2m 18s ✗

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LeetCode 2412 - Minimum Money Required Before Transactions

LeetCode Problem 2412 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the minimum initial money required to complete all transactions in any order . Each transaction is defined by [costi, cashbacki] , meaning that performing the transaction requires at least costi money, and after completing it, we receive cashbacki back. In other words, we must choose a starting amount of money such...

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LeetCode 2160 - Minimum Sum of Four Digit Number After Splitting Digits

LeetCode Problem 2160 Difficulty: 🟢 Easy Topics: Math, Greedy, Sorting Solution Problem Understanding The problem asks us to take a four-digit integer num and split its digits into two new integers such that the sum of these two integers is minimized. We are allowed to use all digits exactly once, and the new integers can have leading zeros . For instance, if the number is 2932 , the digits are...

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Codeforces Round 131 (Div. 2)

Codeforces Round 131 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1600 | Time: 3m 45s Problem Name Rating Tags Solve Time Verified A System of Equations 800 brute-force 56s ✓ B Hometask 1600 brute-force, constructive-algorithms, greedy 2m 49s ✓

Practice › Codeforces Solutions › Codeforces Round 197 (Div. 2) ›

CF 339A - Helpful Maths

CF 339A - Helpful Maths Rating: 800 Tags: greedy, implementation, sortings, strings Solve time: 4m 3s Verified: yes Solution Problem Understanding We are given a single string that represents a sum of small integers. The expression is written using digits and plus signs, where every number is guaranteed to be either 1, 2, or 3. The task is to rearrange the numbers so that the resulting expression is sorted in...

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LeetCode 1975 - Maximum Matrix Sum

LeetCode Problem 1975 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives an n x n integer matrix and allows an operation where we pick any two adjacent cells (sharing a side) and multiply both values by -1 . This operation can be applied any number of times, and the goal is to maximize the total sum of all matrix elements after any sequence of such...

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LeetCode 3107 - Minimum Operations to Make Median of Array Equal to K

LeetCode Problem 3107 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to transform an integer array so that its median becomes exactly k , using the minimum number of operations. In one operation, we may either increase or decrease any single element by 1 . The median is defined after sorting the array in non-decreasing order. For arrays with odd length, the median is...

Practice › Codeforces Solutions › Codeforces Round 246 (Div. 2) ›

CF 432E - Square Tiling

CF 432E - Square Tiling Rating: 2300 Tags: constructive algorithms, greedy Solve time: 2m 40s Verified: yes Solution Problem Understanding We are asked to color an $n \times m$ grid such that every contiguous region of the same color forms a square. Each square can be of any size, as long as it is a perfect square in shape and does not overlap another square of the same color. The...

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Codeforces Round 246 (Div. 2)

Codeforces Round 246 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-2300 | Time: 4m 1s Problem Name Rating Tags Solve Time Verified A Choosing Teams 800 greedy, implementation, sortings 1m 21s ✓ E Square Tiling 2300 constructive-algorithms, greedy 2m 40s ✓

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LeetCode 3273 - Minimum Amount of Damage Dealt to Bob

LeetCode Problem 3273 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution LeetCode 3273 - Minimum Amount of Damage Dealt to Bob Problem Understanding This problem asks us to determine the minimum total damage Bob will receive while fighting a group of enemies. Each enemy has two attributes: damage[i] , the amount of damage they inflict on Bob every second while alive. health[i] , the amount of health they start with....

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Codeforces Round 169 (Div. 2)

Codeforces Round 169 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 2/3 | Rating range: 900-1700 | Time: 4m 36s Problem Name Rating Tags Solve Time Verified A Lunch Rush 900 implementation 1m 30s ✗ C Little Girl and Maximum Sum 1500 data-structures, greedy, implementation 1m 42s ✓ D Little Girl and Maximum XOR 1700 bitmasks, dp, greedy 1m 24s ✓

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CF 140C - New Year Snowmen

CF 140C - New Year Snowmen Rating: 1800 Tags: binary search, data structures, greedy Solve time: 2m Verified: no Solution Problem Understanding We are given a collection of snowballs, each with a specific radius, and our goal is to assemble as many snowmen as possible using these snowballs. Each snowman must be made of exactly three snowballs, and each of those three must have a distinct radius. The input consists...

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Codeforces Round 148 (Div. 2)

Codeforces Round 148 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 1200-1500 | Time: 4m 55s Problem Name Rating Tags Solve Time Verified A Two Bags of Potatoes 1200 greedy, implementation, math 1m 23s ✓ B Easy Tape Programming 1500 brute-force, implementation 3m 32s ✗

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LeetCode 3301 - Maximize the Total Height of Unique Towers

LeetCode Problem 3301 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding We are given an array maximumHeight where maximumHeight[i] represents the largest height that tower i is allowed to have. Our goal is to assign an actual height to every tower such that: Every assigned height is a positive integer. The assigned height of tower i is at most maximumHeight[i] . All assigned heights are distinct. Among all...

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LeetCode 2294 - Partition Array Such That Maximum Difference Is K

LeetCode Problem 2294 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us an integer array nums and an integer k . We must divide the array into one or more subsequences such that every number belongs to exactly one subsequence, and for every subsequence, the difference between its maximum value and minimum value is at most k . The goal is to minimize the number...

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CF 276D - Little Girl and Maximum XOR

CF 276D - Little Girl and Maximum XOR Rating: 1700 Tags: bitmasks, dp, greedy, implementation, math Solve time: 1m 24s Verified: yes Solution Problem Understanding We are given two integers, l and r . We may choose any two numbers a and b such that both lie inside the interval [l, r] and a ≤ b . Among all such pairs, we must compute the maximum possible value of a...

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LeetCode 2573 - Find the String with LCP

LeetCode Problem 2573 Difficulty: 🔴 Hard Topics: Array, String, Dynamic Programming, Greedy, Union-Find, Matrix Solution Problem Understanding The problem gives us an n x n matrix called lcp , where: lcp[i][j] represents the length of the longest common prefix between: the suffix starting at index i the suffix starting at index j If the unknown string is word , then: suffix i is word[i:] suffix j is word[j:] The task...

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Codeforces Round 145 (Div. 1, ACM-ICPC Rules)

Codeforces Round 145 (Div. 1, ACM-ICPC Rules) Type: Div. 1 | Problems: 2 | Verified: 2/2 | Rating range: 2600-2800 | Time: 3m 3s Problem Name Rating Tags Solve Time Verified E Road Repairs 2800 dfs-and-similar, graphs, greedy 1m 58s ✓ F TorCoder 2600 data-structures 1m 5s ✓

Practice › Codeforces Solutions › Codeforces Round 158 (Div. 2) ›

CF 260D - Black and White Tree

CF 260D - Black and White Tree Rating: 2100 Tags: constructive algorithms, dsu, graphs, greedy, trees Solve time: 3m 7s Verified: no Solution Problem Understanding We are given a tree whose structure has been erased, but two pieces of information remain attached to each vertex: its color and a number that equals the total weight of all edges incident to it in the original tree. Every edge connects vertices of...

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Codeforces Round 151 (Div. 2)

Codeforces Round 151 (Div. 2) Type: Div. 2 | Problems: 3 | Verified: 3/3 | Rating range: 900-1600 | Time: 4m 21s Problem Name Rating Tags Solve Time Verified A Buggy Sorting 900 constructive-algorithms, greedy, sortings 1m 8s ✓ C Beauty Pageant 1600 brute-force, constructive-algorithms, greedy 1m 43s ✓ D Colorful Graph 1600 brute-force, dfs-and-similar, graphs 1m 30s ✓

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LeetCode 2659 - Make Array Empty

LeetCode Problem 2659 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Binary Indexed Tree, Segment Tree, Sorting, Ordered Set Solution LeetCode 2659 - Make Array Empty Problem Understanding The problem gives us an array of distinct integers and defines two possible operations: If the first element is currently the smallest value in the array, we remove it. Otherwise, we move the first element to the end of the array. We...

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LeetCode 2517 - Maximum Tastiness of Candy Basket

LeetCode Problem 2517 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution LeetCode 2517 - Maximum Tastiness of Candy Basket Problem Understanding The problem gives us an array price where each element represents the price of a candy. We must choose exactly k distinct candies and maximize the basket's "tastiness". The tastiness of a basket is defined as the minimum absolute difference between the prices of any two candies...

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LeetCode 3219 - Minimum Cost for Cutting Cake II

LeetCode Problem 3219 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding We are given an m x n rectangular cake and need to divide it completely into 1 x 1 pieces. The cake can be cut along predefined horizontal and vertical lines. There are m - 1 possible horizontal cuts and n - 1 possible vertical cuts: horizontalCut[i] is the cost of cutting across horizontal line i verticalCut[j]...

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CF 159B - Matchmaker

CF 159B - Matchmaker Rating: 1100 Tags: *special, greedy, sortings Solve time: 2m 1s Verified: yes Solution Problem Understanding We have two collections of objects. Markers are described by (color, diameter) and caps are also described by (color, diameter) . A cap can be attached to a marker only if the diameters are equal. Among all valid pairings, some are considered “beautiful” when the colors also match. The optimization goal...

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LeetCode 3002 - Maximum Size of a Set After Removals

LeetCode Problem 3002 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution Problem Understanding The problem is asking us to maximize the number of unique elements we can have in a set after removing exactly half of the elements from two arrays nums1 and nums2 . Each array is of even length n , and after removing n/2 elements from each, we insert all remaining elements into a set. Since...

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LeetCode 2598 - Smallest Missing Non-negative Integer After Operations

LeetCode Problem 2598 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy Solution That is a long, structured technical guide with multiple required sections and two full implementations. To keep the quality high and follow your formatting rules exactly, I will provide it in a single comprehensive response. LeetCode 2598 - Smallest Missing Non-negative Integer After Operations Problem Understanding The problem gives us an integer array nums and an integer...

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CF 349B - Color the Fence

CF 349B - Color the Fence Rating: 1700 Tags: data structures, dp, greedy, implementation Solve time: 2m 3s Verified: yes Solution Problem Understanding The problem presents a scenario where Igor wants to paint a number on a fence using a limited amount of paint. Each digit from 1 to 9 consumes a specific amount of paint, given in the array a . Igor cannot use zero. The goal is to...

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Codeforces Round 159 (Div. 2)

Codeforces Round 159 (Div. 2) Type: Div. 2 | Problems: 4 | Verified: 4/4 | Rating range: 1100-1900 | Time: 6m 19s Problem Name Rating Tags Solve Time Verified A Sockets 1100 greedy, implementation, sortings 1m 10s ✓ B Playing Cubes 1300 games, greedy, implementation 1m 23s ✓ C View Angle 1800 brute-force, geometry, math 2m 43s ✓ D Sum 1900 greedy, math 1m 3s ✓

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LeetCode 2834 - Find the Minimum Possible Sum of a Beautiful Array

LeetCode Problem 2834 Difficulty: 🟡 Medium Topics: Math, Greedy Solution LeetCode 2834 - Find the Minimum Possible Sum of a Beautiful Array Problem Understanding We are given two positive integers, n and target . We need to construct an array of exactly n distinct positive integers such that no two different elements add up to target . Among all arrays satisfying these conditions, we want the one with the smallest...

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CF 205B - Little Elephant and Sorting

CF 205B - Little Elephant and Sorting Rating: 1400 Tags: brute force, greedy Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given an array of integers, and one operation consists of choosing a contiguous segment and increasing every element inside that segment by exactly one. We may repeat this operation any number of times. After all operations, we do not need to match a fixed target array;...

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LeetCode 2429 - Minimize XOR

LeetCode Problem 2429 Difficulty: 🟡 Medium Topics: Greedy, Bit Manipulation Solution Problem Understanding The problem is asking us to construct an integer x that satisfies two conditions. First, x must have the same number of set bits (1's in the binary representation) as a given integer num2 . Second, the XOR of x with another integer num1 must be minimized. In other words, we want x XOR num1 to be...

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LeetCode 2116 - Check if a Parentheses String Can Be Valid

LeetCode Problem 2116 Difficulty: 🟡 Medium Topics: String, Stack, Greedy Solution Problem Understanding This problem asks whether a given parentheses string can be transformed into a valid parentheses sequence under certain constraints. We are given two strings: s , containing only '(' and ')' locked , containing only '0' and '1' Both strings have the same length n . At every index: If locked[i] == '1' , then s[i] is...

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CF 416D - Population Size

CF 416D - Population Size Rating: 2400 Tags: greedy, implementation, math Solve time: 1m 23s Verified: yes Solution Problem Understanding We are given a sequence of length $n$, where each position is either a fixed positive integer or unknown (marked as $-1$). The task is to interpret this sequence as being formed by concatenating several arithmetic progressions, one after another. Within each segment, consecutive elements must differ by a constant...

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Codeforces Round 109 (Div. 2)

Codeforces Round 109 (Div. 2) Type: Div. 2 | Problems: 2 | Verified: 1/2 | Rating range: 800-1100 | Time: 5m 59s Problem Name Rating Tags Solve Time Verified A I_love_\%username\% 800 brute-force 4m 24s ✗ B Combination 1100 greedy, sortings 1m 35s ✓

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Codeforces Round 145 (Div. 2, ACM-ICPC Rules)

Codeforces Round 145 (Div. 2, ACM-ICPC Rules) Type: Div. 2 | Problems: 5 | Verified: 2/5 | Rating range: 1000-2000 | Time: 9m 42s Problem Name Rating Tags Solve Time Verified B Reading 1000 sortings 1m 19s ✓ C Weather 1300 dp, implementation 1m 27s ✓ F Fence 1800 dp 1m 5s ✗ G Practice 1600 constructive-algorithms, divide-and-conquer, implementation 2m 54s ✗ H Merging Two Decks 2000 constructive-algorithms, greedy 2m...

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LeetCode 2811 - Check if it is Possible to Split Array

LeetCode Problem 2811 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem asks whether it is possible to split an input array nums into exactly n arrays of size one using a series of valid splits. Each split must take an existing array of length at least two and divide it into two good arrays . An array is considered good if it is either of...

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LeetCode 2592 - Maximize Greatness of an Array

LeetCode Problem 2592 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Here is the complete, detailed technical solution guide for LeetCode 2592 - Maximize Greatness of an Array following your formatting requirements. Problem Understanding The problem gives us an integer array nums and asks us to permute it into a new array perm such that the number of indices i for which perm[i] > nums[i] is maximized. This...

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Codeforces Round 104 (Div. 1)

Codeforces Round 104 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2900 | Time: 10m 29s Problem Name Rating Tags Solve Time Verified A Lucky Conversion 1200 greedy, implementation 2m 2s ✓ B Lucky Number 2 1800 constructive-algorithms 2m 22s ✓ C Lucky Subsequence 2100 combinatorics, dp, math 2m 5s ✓ D Lucky Pair 2900 combinatorics, data-structures, implementation 1m 48s ✗ E Lucky Queries...

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LeetCode 2578 - Split With Minimum Sum

LeetCode Problem 2578 Difficulty: 🟢 Easy Topics: Math, Greedy, Sorting Solution Problem Understanding The problem asks us to take a positive integer num and split its digits into two non-negative integers num1 and num2 such that the sum num1 + num2 is minimized. Importantly, the digits of num must be entirely used between num1 and num2 , but their order can be rearranged, and leading zeros are allowed in both...

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Abbyy Cup 2.0 - Final (unofficial)

Abbyy Cup 2.0 - Final (unofficial) Type: Special | Problems: 17 | Verified: 14/17 | Rating range: 1600-2700 | Time: 25m 3s Problem Name Rating Tags Solve Time Verified A1 Beaver's Calculator 1.0 1600 greedy 1m 9s ✓ A2 Beaver's Calculator 1.0 1800 greedy 1m 11s ✓ A3 Beaver's Calculator 1.0 2000 greedy 1m 43s ✓ B1 Military Trainings 1600 - 1m 47s ✓ B2 Military Trainings 1900 - 1m...

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CF 203C - Photographer

CF 203C - Photographer Rating: 1400 Tags: greedy, sortings Solve time: 1m 5s Verified: yes Solution Problem Understanding Each client describes a fixed amount of work Valera must perform: a certain number of low quality photos and a certain number of high quality photos. Every low quality photo consumes a fixed amount of camera memory, and every high quality photo consumes a (possibly larger) fixed amount. Once a photo is...

Practice › Codeforces Solutions › Codeforces Round 151 (Div. 2) ›

CF 246C - Beauty Pageant

CF 246C - Beauty Pageant Rating: 1600 Tags: brute force, constructive algorithms, greedy Solve time: 1m 43s Verified: yes Solution Problem Understanding We are asked to select soldiers from a battalion to participate in a beauty pageant over several days. Each soldier has a unique beauty value. On each day, we must send a group of soldiers whose combined beauty is unique compared to the other days. The detachment for...

Practice › Codeforces Solutions › Codeforces Round 194 (Div. 1) ›

CF 333A - Secrets

CF 333A - Secrets Rating: 1600 Tags: greedy Solve time: 1m 42s Verified: yes Solution Problem Understanding We are asked to determine how a buyer, constrained to coins whose values are powers of three (1, 3, 9, 27, …), could pay an amount n marks in such a way that he cannot pay n exactly and must overpay using the minimum number of coins possible. The input is a single...

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CF 141C - Queue

CF 141C - Queue Rating: 1800 Tags: constructive algorithms, greedy, sortings Solve time: 2m 24s Verified: no Solution Problem Understanding Each person remembers a single number, how many taller people stood before them in the queue. We no longer know either the original order or the actual heights. The task is to reconstruct any valid queue order together with heights that satisfy every person's remembered value. Suppose a person has...

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Codeforces Round 200 (Div. 1)

Codeforces Round 200 (Div. 1) Type: Div. 1 | Problems: 1 | Verified: 0/1 | Rating range: 1900-1900 | Time: 16m 21s Problem Name Rating Tags Solve Time Verified C Read Time 1900 binary-search, greedy, two-pointers 16m 21s ✗

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LeetCode 2208 - Minimum Operations to Halve Array Sum

LeetCode Problem 2208 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding This problem asks us to repeatedly reduce numbers in an array until the total sum of the array has been reduced by at least half , while using the minimum number of operations . In one operation, we may choose any number currently in the array and replace it with exactly half of its value....

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CF 166C - Median

CF 166C - Median Rating: 1500 Tags: greedy, math, sortings Solve time: 1m 37s Verified: yes Solution Problem Understanding We start with an array of integers and a target value x . We may append any number of extra integers to the array, and we want the median of the final array to become exactly x . The task is to compute the smallest number of added elements needed to...

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Codeforces Round #FF (Div. 2)

Codeforces Round #FF (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 1000-1000 | Time: 1m 11s Problem Name Rating Tags Solve Time Verified B DZY Loves Strings 1000 greedy, implementation 1m 11s ✓

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Codeforces Round 160 (Div. 1)

Codeforces Round 160 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 3/3 | Rating range: 1400-2800 | Time: 6m 1s Problem Name Rating Tags Solve Time Verified A Maxim and Discounts 1400 greedy, sortings 3m 10s ✓ C Maxim and Matrix 2000 constructive-algorithms, dp, math 1m 11s ✓ E Maxim and Calculator 2800 brute-force, dp, two-pointers 1m 40s ✓

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3022 - Minimize OR of Remaining Elements Using Operations

LeetCode Problem 3022 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents an array nums of non-negative integers and an integer k . You are allowed to perform at most k operations, where each operation merges two adjacent elements using the bitwise AND operator. The goal is to minimize the bitwise OR of all remaining elements after performing these operations. Formally, if nums = [a_0,...

Practice › Codeforces Solutions › Codeforces Round 113 (Div. 2) ›

CF 166D - Shoe Store

CF 166D - Shoe Store Rating: 2500 Tags: dp, graph matchings, greedy, sortings, two pointers Solve time: 2m 34s Verified: yes Solution Problem Understanding We have a collection of shoes, where every shoe has a unique size and a price. We also have customers, where each customer has a budget and a foot size. A customer can buy a shoe only if two conditions hold. The first condition is financial:...

Practice › Codeforces Solutions › Codeforces Round 145 (Div. 2, ACM-ICPC Rules) ›

CF 234H - Merging Two Decks

CF 234H - Merging Two Decks Rating: 2000 Tags: constructive algorithms, greedy Solve time: 2m 57s Verified: no Solution Problem Understanding We are given two stacks of cards, each card either face up or face down. The goal is to merge the decks into a single stack in a way that preserves the relative order of cards within each original deck, and then perform a series of operations to turn...

Practice › Codeforces Solutions ›

Codeforces Round 254 (Div. 1)

Codeforces Round 254 (Div. 1) Type: Div. 1 | Problems: 3 | Verified: 2/3 | Rating range: 1600-2700 | Time: 4m 8s Problem Name Rating Tags Solve Time Verified A DZY Loves Physics 1600 greedy, math 1m 32s ✓ D DZY Loves Strings 2500 binary-search, hashing, strings 1m 6s ✓ E DZY Loves Planting 2700 binary-search, dsu, trees 1m 30s ✗

Practice › Codeforces Solutions › Croc Champ 2013 - Finals (online version, Div. 1) ›

CF 309E - Sheep

CF 309E - Sheep Rating: 2900 Tags: binary search, greedy Solve time: 2m 34s Verified: yes Solution Problem Understanding We have a collection of sheep, each identified by a unique number from 1 to n . Every sheep has a range of meadow regions it likes, represented as an interval $[l_i, r_i]$. In the morning, the first shepherd ties any pair of sheep whose preferred regions overlap. In graph terms,...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1989 - Maximum Number of People That Can Be Caught in Tag

LeetCode Problem 1989 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy Solution Problem Understanding The problem describes a line of people represented by a binary array team , where each index corresponds to a person. A value of 1 indicates a person who is “it”, and a value of 0 indicates a person who is not “it”. Each “it” person can catch at most one non-“it” person, and only if...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2931 - Maximum Spending After Buying Items

LeetCode Problem 2931 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue), Matrix Solution LeetCode 2931 - Maximum Spending After Buying Items Problem Understanding We are given an m × n matrix values where each row represents a shop and each column represents an item in that shop. The important property is that every row is sorted in non-increasing order: values[i][0] >= values[i][1] >= ... >= values[i][n-1] When buying...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2434 - Using a Robot to Print the Lexicographically Smallest String

LeetCode Problem 2434 Difficulty: 🟡 Medium Topics: Hash Table, String, Stack, Greedy Solution Problem Understanding In this problem, we are given a string s and a robot that manages another temporary string t . Initially, t is empty. The robot repeatedly performs one of two allowed operations: First, it may remove the first character from s and append it to the end of t . Second, it may remove the...

Practice › Codeforces Solutions ›

Testing Round 6

Testing Round 6 Type: Special | Problems: 4 | Verified: 1/4 | Rating range: 800-2300 | Time: 10m 15s Problem Name Rating Tags Solve Time Verified A Candies 800 implementation 3m 20s ✗ B Optimizer 2100 data-structures, greedy, sortings 1m 26s ✓ C White, Black and White Again 2100 combinatorics, number-theory 3m 20s ✗ D Polygon 2300 constructive-algorithms, geometry 2m 9s ✗

Practice › Codeforces Solutions ›

Codeforces Round 197 (Div. 2)

Codeforces Round 197 (Div. 2) Type: Div. 2 | Problems: 1 | Verified: 1/1 | Rating range: 800-800 | Time: 4m 3s Problem Name Rating Tags Solve Time Verified A Helpful Maths 800 greedy, implementation, sortings 4m 3s ✓

Practice › Codeforces Solutions › Codeforces Round 154 (Div. 2) ›

CF 253C - Text Editor

CF 253C - Text Editor Rating: 1600 Tags: data structures, dfs and similar, graphs, greedy, shortest paths Solve time: 53s Verified: yes Solution Problem Understanding We are given a text editor that stores several lines of text. Each line has a known length, and the cursor is allowed to sit not only on characters but also in the gap positions before the first character and after the last character. So...

Practice › Codeforces Solutions ›

Codeforces Round 105 (Div. 2)

Codeforces Round 105 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-1900 | Time: 9m 21s Problem Name Rating Tags Solve Time Verified A Insomnia cure 800 constructive-algorithms, implementation, math 1m 34s ✗ B Escape 1500 implementation, math 1m 12s ✓ C Terse princess 1700 constructive-algorithms, greedy 2m 14s ✗ D Bag of mice 1800 dp, games, math 1m 55s ✓ E Porcelain 1900...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2548 - Maximum Price to Fill a Bag

LeetCode Problem 2548 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem is asking us to maximize the total price of items placed in a bag with a fixed capacity. Each item is defined by a price and a weight, but unlike traditional knapsack problems, items can be divided proportionally , meaning we can take fractions of an item. Specifically, if we take a fraction f of...

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LeetCode 2202 - Maximize the Topmost Element After K Moves

LeetCode Problem 2202 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding In this problem, we are given a pile of integers represented as an array nums , where nums[0] is the current top element of the pile. We must perform exactly k moves, and in each move we are allowed to do one of two operations: Remove the current top element from the pile. Add back any previously removed...

Practice › Codeforces Solutions › Codeforces Round 148 (Div. 2) ›

CF 239A - Two Bags of Potatoes

CF 239A - Two Bags of Potatoes Rating: 1200 Tags: greedy, implementation, math Solve time: 1m 23s Verified: yes Solution Problem Understanding We know the second bag contains y potatoes. The first bag originally contained some positive number x , but that value was lost. The only remaining information is that the total number of potatoes, x + y , was divisible by k and did not exceed n ....

Practice › Codeforces Solutions ›

Codeforces Round 100

Codeforces Round 100 Type: Special | Problems: 6 | Verified: 3/6 | Rating range: 1700-2600 | Time: 12m 15s Problem Name Rating Tags Solve Time Verified A New Year Table 1700 geometry, math 1m 45s ✓ B New Year Cards 1800 brute-force, greedy, implementation 2m 41s ✗ C New Year Snowmen 1800 binary-search, data-structures, greedy 2m ✗ D New Year Contest 1800 greedy, sortings 1m 55s ✓ E New Year...

Practice › LeetCode › LeetCode 15xx ›

LeetCode 1520 - Maximum Number of Non-Overlapping Substrings

LeetCode Problem 1520 Difficulty: 🔴 Hard Topics: Hash Table, String, Greedy, Sorting Solution LeetCode 1520 - Maximum Number of Non-Overlapping Substrings Problem Understanding This problem asks us to select as many non-overlapping substrings as possible from a given lowercase string s , while satisfying a strict containment rule. A substring is considered valid only if, whenever it contains a character c , it also contains every occurrence of c that...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 420 - Strong Password Checker

LeetCode Problem 420 Difficulty: 🔴 Hard Topics: String, Greedy, Heap (Priority Queue) Solution Strong Password Checker Problem Understanding The problem asks us to determine the minimum number of operations required to transform a given password into a "strong" password according to three rules. A strong password must satisfy all of the following conditions: The password length must be between 6 and 20 characters inclusive. The password must contain at least...

Practice › Codeforces Solutions ›

Codeforces Beta Round 72 (Div. 1 Only)

Codeforces Beta Round 72 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1300-2800 | Time: 9m 17s Problem Name Rating Tags Solve Time Verified A Magical Array 1300 math 1m 28s ✓ B Doctor 1800 binary-search, math, sortings 1m 37s ✓ C Track 2400 graphs, greedy, shortest-paths 2m 22s ✓ D Numbers 2400 dp, math, number-theory 2m 7s ✓ E Two Subsequences 2800...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1753 - Maximum Score From Removing Stones

LeetCode Problem 1753 Difficulty: 🟡 Medium Topics: Math, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem is a combinatorial game involving three piles of stones with counts a , b , and c . In each move, you are allowed to pick two different non-empty piles and remove one stone from each , earning 1 point per move. The game ends when fewer than two piles have stones left....

Practice › LeetCode › LeetCode 03xx ›

LeetCode 330 - Patching Array

LeetCode Problem 330 Difficulty: 🔴 Hard Topics: Array, Greedy Solution LeetCode 330 - Patching Array Problem Understanding The problem gives us a sorted array of positive integers, nums , and a target integer n . We are allowed to insert additional numbers into the array, called patches. The goal is to ensure that every number in the range [1, n] can be formed as the sum of some subset of...

Practice › Codeforces Solutions ›

Codeforces Beta Round 27 (Codeforces format, Div. 2)

Codeforces Beta Round 27 (Codeforces format, Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2200 | Time: 6m 38s Problem Name Rating Tags Solve Time Verified A Next Test 1200 implementation, sortings 1m 13s ✓ B Tournament 1300 bitmasks, brute-force, dfs-and-similar 1m 3s ✓ C Unordered Subsequence 1900 constructive-algorithms, greedy 1m 18s ✗ D Ring Road 2 2200 2-sat, dfs-and-similar, dsu 1m 30s ✓...

Practice › Codeforces Solutions ›

Codeforces Beta Round 97 (Div. 1)

Codeforces Beta Round 97 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 9m 14s Problem Name Rating Tags Solve Time Verified A Replacement 1300 greedy, implementation, sortings 1m 34s ✓ B Rectangle and Square 1600 brute-force, geometry, math 2m 3s ✓ C Zero-One 1900 constructive-algorithms, games, greedy 1m 50s ✓ D Cycle 2500 brute-force, dfs-and-similar, implementation 1m 50s ✓ E Weak...

Practice › Codeforces Solutions ›

Codeforces Beta Round 48

Codeforces Beta Round 48 Type: Beta | Problems: 6 | Verified: 4/6 | Rating range: 1300-2800 | Time: 13m 36s Problem Name Rating Tags Solve Time Verified A Cheaterius's Problem 1300 implementation 1m 37s ✓ B bHTML Tables Analisys 1700 expression-parsing 3m 37s ✓ C Three Base Stations 1800 binary-search, greedy 2m 13s ✗ D Geometrical problem 2200 implementation 1m 55s ✓ E Pentagon 2400 combinatorics, graphs, matrices 2m 2s...

Practice › Codeforces Solutions ›

Codeforces Beta Round 71

Codeforces Beta Round 71 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1200-2900 | Time: 7m 45s Problem Name Rating Tags Solve Time Verified A Bus Game 1200 greedy 1m 20s ✓ B Colorful Field 1400 implementation, sortings 1m 19s ✓ C Beaver 1800 data-structures, dp, greedy 1m 27s ✓ D Password 2800 bitmasks, dp, shortest-paths 2m 11s ✓ E Security System 2900 math 1m 28s ✓

Practice › Codeforces Solutions › Codeforces Beta Round 18 (Div. 2 Only) ›

CF 18D - Seller Bob

CF 18D - Seller Bob Rating: 2000 Tags: brute force, dp, greedy Solve time: 1m 54s Verified: yes Solution Problem Understanding Bob experiences one event per day. A day is either a prize day or a customer day. On a prize day, Bob receives a memory stick of size $2^x$. He may either keep it or immediately give it away. He is never allowed to store more than one stick...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1686 - Stone Game VI

LeetCode Problem 1686 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting, Heap (Priority Queue), Game Theory Solution This is a long, structured technical guide with multiple substantial sections, worked examples, code, tables, and test coverage. To make sure it is complete and properly formatted according to your rules, I should generate it as a document/canvas rather than risk truncation in chat. I can produce the full guide for LeetCode 1686...

Practice › LeetCode › LeetCode 10xx ›

LeetCode 1058 - Minimize Rounding Error to Meet Target

LeetCode Problem 1058 Difficulty: 🟡 Medium Topics: Array, Math, String, Greedy, Sorting Solution Problem Understanding The problem asks us to round an array of decimal prices to integers such that the sum of the rounded numbers equals a given target, while minimizing the total rounding error. Each price can be rounded either down ( Floor ) or up ( Ceil ). The rounding error for each price is defined as...

Practice › Codeforces Solutions ›

Codeforces Beta Round 87 (Div. 1 Only)

Codeforces Beta Round 87 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 900-2600 | Time: 11m 15s Problem Name Rating Tags Solve Time Verified A Party 900 dfs-and-similar, graphs, trees 1m 51s ✓ B Lawnmower 1500 greedy, sortings 1m 30s ✓ C Plumber 2200 math 2m 56s ✗ D Unambiguous Arithmetic Expression 2600 dp, expression-parsing 2m 6s ✓ E Linear Kingdom Races 2400...

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81C - Average Score

CF 81C - Average Score Rating: 1700 Tags: greedy, math, sortings Solve time: 3m 31s Verified: yes Solution Problem Understanding We are given a sequence of marks, but the subject for each mark was lost. There are only two subjects, and we know exactly how many marks belong to each one. If subject 1 must receive a marks, then subject 2 automatically receives b = n - a marks. Our...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2027 - Minimum Moves to Convert String

LeetCode Problem 2027 Difficulty: 🟢 Easy Topics: String, Greedy Solution Problem Understanding The problem asks us to transform a string s containing only characters 'X' and 'O' so that all characters become 'O' . A move consists of selecting three consecutive characters and converting them to 'O' . If a character is already 'O' , it remains unchanged. The goal is to determine the minimum number of moves required to...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 921 - Minimum Add to Make Parentheses Valid

LeetCode Problem 921 Difficulty: 🟡 Medium Topics: String, Stack, Greedy Solution Problem Understanding The problem asks us to determine the minimum number of parentheses insertions required to make a given string of parentheses valid. A string of parentheses is considered valid if every opening parenthesis '(' has a matching closing parenthesis ')' and the pairs are properly nested. The input s is a string consisting only of '(' and ')'...

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LeetCode 605 - Can Place Flowers

LeetCode Problem 605 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem gives us a binary array called flowerbed , where: 0 represents an empty plot 1 represents a plot that already contains a flower We are also given an integer n , which represents how many new flowers we want to plant. The key restriction is that flowers cannot be planted in adjacent plots . This means...

Practice › Codeforces Solutions › Codeforces Beta Round 5 ›

CF 5C - Longest Regular Bracket Sequence

CF 5C - Longest Regular Bracket Sequence Rating: 1900 Tags: constructive algorithms, data structures, dp, greedy, sortings, strings Solve time: 1m 21s Verified: yes Solution Problem Understanding We are given a string made only of ( and ) . Among all contiguous substrings, we need to find the maximum length of a substring that forms a valid bracket sequence. We also need to count how many substrings achieve that maximum...

Practice › LeetCode › LeetCode 13xx ›

LeetCode 1382 - Balance a Binary Search Tree

LeetCode Problem 1382 Difficulty: 🟡 Medium Topics: Divide and Conquer, Greedy, Tree, Depth-First Search, Binary Search Tree, Binary Tree Solution Here is a complete, detailed technical solution guide for LeetCode 1382 - Balance a Binary Search Tree , following all your formatting rules. Problem Understanding The problem asks us to take a binary search tree (BST) that may be unbalanced and produce a new BST that is balanced while preserving...

Practice › Codeforces Solutions › Codeforces Beta Round 41 ›

CF 42A - Guilty --- to the kitchen!

CF 42A - Guilty --- to the kitchen! Rating: 1400 Tags: greedy, implementation Solve time: 1m 32s Verified: yes Solution Problem Understanding We want to cook soup using several ingredients that must appear in a fixed ratio. If the recipe says the proportions are a1, a2, ..., an , then the final soup must contain: a1 * x, a2 * x, ..., an * x litres of each ingredient for...

Practice › LeetCode › LeetCode 11xx ›

LeetCode 1130 - Minimum Cost Tree From Leaf Values

LeetCode Problem 1130 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to construct a binary tree from an input array arr of positive integers, where each integer represents a leaf node in an in-order traversal. Every non-leaf node has exactly two children, and its value is calculated as the product of the largest leaf values in its left and right...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1846 - Maximum Element After Decreasing and Rearranging

LeetCode Problem 1846 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem provides an array of positive integers and asks us to perform operations to transform it so that two conditions are satisfied: the first element must be 1 , and the absolute difference between adjacent elements cannot exceed 1 . We are allowed to decrease elements and rearrange the array. The ultimate goal is to maximize...

Practice › Codeforces Solutions › Codeforces Beta Round 40 (Div. 2) ›

CF 41E - 3-cycles

CF 41E - 3-cycles Rating: 1900 Tags: constructive algorithms, graphs, greedy Solve time: 1m 48s Verified: no Solution Problem Understanding We need to build an undirected graph on n cities such that no triangle exists. A triangle means three distinct cities where every pair is directly connected. Among all graphs with no 3-cycles, we want the one with the maximum possible number of roads, and we must also print one...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 253 - Meeting Rooms II

LeetCode Problem 253 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum Solution Problem Understanding The problem gives us a list of meeting intervals where each interval is represented as [start, end] . Each interval describes the time range during which a meeting occupies a conference room. The goal is to determine the minimum number of conference rooms needed so that all meetings can take...

Practice › Codeforces Solutions › Codeforces Beta Round 76 (Div. 1 Only) ›

CF 93B - End of Exams

CF 93B - End of Exams Rating: 1900 Tags: greedy Solve time: 1m 43s Verified: no Solution Problem Understanding We are asked to distribute milk from a set of bottles into cups such that each bottle contributes to at most two cups, and all cups end up with the same total volume. Specifically, we have n bottles, each containing w units of milk, and m friends who each receive one...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1405 - Longest Happy String

LeetCode Problem 1405 Difficulty: 🟡 Medium Topics: String, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to construct the longest possible string using only the characters 'a' , 'b' , and 'c' , while satisfying a very important restriction: the string cannot contain three consecutive identical characters. In other words, substrings like "aaa" , "bbb" , and "ccc" are forbidden. We are given three integers: a ,...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 769 - Max Chunks To Make Sorted

LeetCode Problem 769 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding This problem is asking us to determine the maximum number of contiguous chunks into which we can split an array such that sorting each chunk individually and concatenating them results in a fully sorted array. The input array arr is a permutation of integers from 0 to n-1 , meaning it contains each integer...

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Codeforces Beta Round 47

Codeforces Beta Round 47 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 800-2300 | Time: 6m 55s Problem Name Rating Tags Solve Time Verified A Domino piling 800 greedy, math 1m 5s ✓ B Choosing Symbol Pairs 1500 strings 1m 15s ✓ C Happy Farm 5 2000 geometry 55s ✓ D Bombing 2100 binary-search, dp, probabilities 1m 42s ✗ E Square Equation Roots 2300 math 1m 58s...

Practice › LeetCode › LeetCode 12xx ›

LeetCode 1253 - Reconstruct a 2-Row Binary Matrix

LeetCode Problem 1253 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding The problem asks us to reconstruct a binary matrix with exactly two rows and n columns given three constraints: the sum of elements in the upper row ( upper ), the sum of elements in the lower row ( lower ), and the sum of elements in each column ( colsum ). Each element in the matrix...

Practice › LeetCode › LeetCode 10xx ›

LeetCode 1054 - Distant Barcodes

LeetCode Problem 1054 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting Solution Problem Understanding The problem is asking us to rearrange a list of barcodes so that no two adjacent barcodes are the same. The input is an array barcodes of integers where each integer represents a type of barcode. The output should be a rearranged array that satisfies the adjacency constraint. The constraints specify...

Practice › Codeforces Solutions › Unknown Language Round 2 ›

CF 72A - Goshtasp, Vishtasp and Eidi

CF 72A - Goshtasp, Vishtasp and Eidi Rating: 1800 Tags: *special, greedy, math Solve time: 1m 18s Verified: yes Solution Problem Understanding The problem asks us to decide whether a positive integer $n$ can be represented as a sum of distinct integers, where each integer is either 1 or a prime number. If such a representation exists, we need to produce one that is lexicographically largest. Lexicographically largest means that,...

Practice › LeetCode › LeetCode 08xx ›

LeetCode 861 - Score After Flipping Matrix

LeetCode Problem 861 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Matrix Solution Problem Understanding The problem provides an m x n binary matrix, grid , where each element is either 0 or 1 . You are allowed to perform a move , which consists of selecting any row or column and flipping all its values - turning every 0 into a 1 and every 1 into a 0 ....

Practice › LeetCode › LeetCode 04xx ›

LeetCode 409 - Longest Palindrome

LeetCode Problem 409 Difficulty: 🟢 Easy Topics: Hash Table, String, Greedy Solution Problem Understanding The problem asks us to find the length of the longest palindrome that can be constructed using the characters of a given string s . A palindrome is a string that reads the same forwards and backwards. The input string s contains only lowercase and uppercase English letters, and letter case matters, so 'A' and 'a'...

Practice › Codeforces Solutions › Codeforces Beta Round 42 (Div. 2) ›

CF 43C - Lucky Tickets

CF 43C - Lucky Tickets Rating: 1300 Tags: greedy Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given a collection of ticket pieces. Each piece is a number, representing the fragment of a ticket that was originally divisible by three. The problem asks us to reconstruct the maximum number of lucky tickets we can from these pieces. A lucky ticket is defined as a number divisible by...

Practice › LeetCode › LeetCode 01xx ›

LeetCode 135 - Candy

LeetCode Problem 135 Difficulty: 🔴 Hard Topics: Array, Greedy Solution LeetCode 135, Candy Problem Understanding This problem asks us to distribute candies to children standing in a line, based on their rating values. Each child must receive at least one candy, and any child with a higher rating than an adjacent neighbor must receive strictly more candies than that neighbor. The input is an integer array ratings , where ratings[i]...

Practice › Codeforces Solutions › Codeforces Round 933 (Div. 3) ›

CF 1941F - Rudolf and Imbalance

CF 1941F - Rudolf and Imbalance Rating: 1800 Tags: binary search, greedy, sortings, two pointers Solve time: 1m 36s Verified: yes Solution Problem Understanding We start with a strictly increasing array of problem complexities. The imbalance of the set is defined as the largest difference between two neighboring elements after sorting. We are allowed to insert at most one additional problem. The new problem must have complexity d_i + f_j...

Practice › Codeforces Solutions ›

Codeforces Beta Round 66

Codeforces Beta Round 66 Type: Beta | Problems: 6 | Verified: 6/6 | Rating range: 1600-2900 | Time: 12m 59s Problem Name Rating Tags Solve Time Verified A The Elder Trolls IV: Oblivon 1600 greedy, math 1m 48s ✓ B Need For Brake 2000 binary-search, greedy, sortings 2m 9s ✓ C LionAge II 1800 dp 1m 27s ✓ D FreeDiv 2200 dfs-and-similar, graphs, greedy 2m 38s ✓ E Morrowindows 2400...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1465 - Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts

LeetCode Problem 1465 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution LeetCode 1465 - Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts Problem Understanding This problem gives us a rectangular cake with height h and width w . We are also given two arrays: horizontalCuts , which contains the positions of horizontal cuts measured from the top edge verticalCuts , which contains the positions of vertical...

Practice › Codeforces Solutions › Codeforces Beta Round 31 (Div. 2, Codeforces format) ›

CF 31B - Sysadmin Bob

CF 31B - Sysadmin Bob Rating: 1500 Tags: greedy, implementation, strings Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a single string that represents multiple email addresses concatenated together with no separators. Each email address has the form A@B , where A and B are non-empty strings consisting of lowercase Latin letters. Our task is to split the string into a sequence of valid email addresses....

Practice › LeetCode › LeetCode 03xx ›

LeetCode 397 - Integer Replacement

LeetCode Problem 397 Difficulty: 🟡 Medium Topics: Dynamic Programming, Greedy, Bit Manipulation, Memoization Solution LeetCode 397 - Integer Replacement Problem Understanding The problem gives us a positive integer n and asks for the minimum number of operations required to transform it into 1 . At every step, we are allowed to apply one of two rules: If the number is even, we must divide it by 2 If the number...

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LeetCode 1400 - Construct K Palindrome Strings

LeetCode Problem 1400 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Counting Solution Problem Understanding The problem is asking whether a given string s can be rearranged to form exactly k non-empty palindrome strings using all characters in s . In other words, we need to partition s into k palindromes such that each character of s is used exactly once. A palindrome is a string that reads the same...

Practice › LeetCode › LeetCode 08xx ›

LeetCode 857 - Minimum Cost to Hire K Workers

LeetCode Problem 857 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding In this problem, we are given two arrays, quality and wage , where each index represents a worker. The value quality[i] describes how much work or contribution the i-th worker provides, while wage[i] describes the minimum amount that worker is willing to accept. We must hire exactly k workers, and the group must satisfy...

Practice › Codeforces Solutions ›

Codeforces Beta Round 41

Codeforces Beta Round 41 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1400-2700 | Time: 10m 20s Problem Name Rating Tags Solve Time Verified A Guilty --- to the kitchen! 1400 greedy, implementation 1m 32s ✓ B Game of chess unfinished 1700 implementation 2m 3s ✓ C Safe cracking 2200 brute-force, constructive-algorithms 1m 2s ✓ D Strange town 2300 constructive-algorithms, math 1m 50s ✗ E Baldman and...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 714 - Best Time to Buy and Sell Stock with Transaction Fee

LeetCode Problem 714 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution LeetCode 714, Best Time to Buy and Sell Stock with Transaction Fee Problem Understanding This problem asks us to maximize profit from stock trading over a sequence of days, where each transaction incurs a fixed fee. The input array prices represents the stock price on each day, and fee represents the transaction fee charged for every completed buy-sell...

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Yandex.Algorithm 2011: Round 1

Yandex.Algorithm 2011: Round 1 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1300-2600 | Time: 11m 13s Problem Name Rating Tags Solve Time Verified A Domino 1300 constructive-algorithms, implementation 2m 9s ✓ B Embassy Queue 1800 data-structures, greedy 2m 1s ✓ C Petya and Tree 2200 binary-search, dfs-and-similar, probabilities 2m 4s ✓ D Sum of Medians 2300 binary-search, brute-force, data-structures 1m 18s ✓ E Guard Towers 2600...

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CF 74B - Train

CF 74B - Train Rating: 1500 Tags: dp, games, greedy Solve time: 2m 11s Verified: yes Solution Problem Understanding The train has n wagons arranged in a line. The controller moves deterministically: every minute he walks one wagon in his current direction, and when he reaches either end he reverses direction. His path is completely fixed once we know the initial wagon and direction. The stowaway behaves differently depending on...

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LeetCode 646 - Maximum Length of Pair Chain

LeetCode Problem 646 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem gives us an array of integer pairs, where each pair represents an interval-like relationship of the form [left, right] . Every pair satisfies the condition left < right . We want to build the longest possible chain of pairs. A pair [c, d] can follow another pair [a, b] only if: b <...

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LeetCode 757 - Set Intersection Size At Least Two

LeetCode Problem 757 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to find the minimum size of a set of integers, nums , such that each given interval [starti, endi] contains at least two integers from nums . Each interval is represented as a closed interval, meaning all integers between starti and endi inclusive belong to that interval. The goal is to construct nums...

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CF 77C - Beavermuncher-0xFF

CF 77C - Beavermuncher-0xFF Rating: 2100 Tags: dfs and similar, dp, dsu, greedy, trees Solve time: 2m 30s Verified: no Solution Problem Understanding We have a tree where each vertex initially contains some number of beavers. The robot starts at a fixed vertex s . Every time it traverses an edge from u to v , it immediately eats exactly one beaver at v . If v already has zero...

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LeetCode 767 - Reorganize String

LeetCode Problem 767 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting, Heap (Priority Queue), Counting Solution Problem Understanding The problem asks us to rearrange the characters of a given string s such that no two adjacent characters are the same. The input is a string of lowercase English letters with a length between 1 and 500. The output should be either a valid rearrangement that satisfies the adjacency constraint...

Practice › Codeforces Solutions › Codeforces Beta Round 87 (Div. 1 Only) ›

CF 115B - Lawnmower

CF 115B - Lawnmower Rating: 1500 Tags: greedy, sortings Solve time: 1m 30s Verified: yes Solution Problem Understanding We are given a rectangular garden represented as an n × m grid. Each cell contains either grass, which does not require mowing, or weeds, which do. We start at the top-left corner of the garden, always on grass, and initially facing right. The lawnmower can move one step in the direction...

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LeetCode 948 - Bag of Tokens

LeetCode Problem 948 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem gives us a collection of tokens, where each token has a numeric value. We also start with an initial amount of power and an initial score of 0 . Every token can be used at most once, and each token can be played in exactly one of two ways. If we play a...

Practice › Codeforces Solutions › Codeforces Beta Round 37 ›

CF 37E - Trial for Chief

CF 37E - Trial for Chief Rating: 2600 Tags: graphs, greedy, shortest paths Solve time: 1m 43s Verified: yes Solution Problem Understanding We are given a rectangular slab divided into an $N \times M$ grid of squares. Each square is either black or white in the final design, which is provided as input. The slab initially starts entirely white. Every day, a pretender can repaint a connected region of squares...

Practice › Codeforces Solutions › Codeforces Beta Round 12 (Div 2 Only) ›

CF 12C - Fruits

CF 12C - Fruits Rating: 1100 Tags: greedy, implementation, sortings Solve time: 1m 2s Verified: yes Solution Problem Understanding Valera has a shopping list containing a number of fruits, possibly with duplicates if he wants more than one of the same type. At the market, the stall has n types of fruits and n price tags, but the tags are not yet attached to the fruits. Each tag represents the...

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Codeforces Beta Round 76 (Div. 1 Only)

Codeforces Beta Round 76 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1700-2600 | Time: 10m 8s Problem Name Rating Tags Solve Time Verified A Frames 1700 implementation 1m 51s ✓ B End of Exams 1900 greedy 1m 43s ✗ C Azembler 2500 brute-force, implementation 2m 1s ✓ D Flags 2500 dp, math, matrices 3m 28s ✗ E Lostborn 2600 dp, math, number-theory...

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Codeforces Beta Round 33 (Codeforces format)

Codeforces Beta Round 33 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1200-2600 | Time: 18m 29s Problem Name Rating Tags Solve Time Verified A What is for dinner? 1200 greedy, implementation 3m 53s ✓ B String Problem 1800 shortest-paths 7m 1s ✓ C Wonderful Randomized Sum 1800 greedy 3m 6s ✓ D Knights 2000 geometry, graphs, shortest-paths 1m 32s ✓ E Helper 2600 -...

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All-Ukrainian School Olympiad in Informatics

All-Ukrainian School Olympiad in Informatics Type: Special | Problems: 6 | Verified: 5/6 | Rating range: 1700-2700 | Time: 12m 33s Problem Name Rating Tags Solve Time Verified A Gift 2200 dsu, graphs, sortings 2m 12s ✓ B Mice 2100 greedy, two-pointers 1m 53s ✗ C Mutation 2700 bitmasks, dp, math 2m 6s ✓ D Plus and xor 1700 dp, greedy, math 1m 46s ✓ E Points 1700 implementation, math...

Practice › Codeforces Solutions › Codeforces Beta Round 74 (Div. 2 Only) ›

CF 90A - Cableway

CF 90A - Cableway Rating: 1000 Tags: greedy, math Solve time: 1m 33s Verified: yes Solution Problem Understanding The cableway sends one cablecar every minute, and the colors repeat in a fixed cycle: red -> green -> blue -> red -> ... Each cablecar can carry at most two students, and every ride takes exactly 30 minutes to reach the top. We are given three groups of students. One group...

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LeetCode 1665 - Minimum Initial Energy to Finish Tasks

LeetCode Problem 1665 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us a list of tasks, where each task is represented as [actual, minimum] . For every task: minimum is the amount of energy we must currently have before we are allowed to start the task. actual is the amount of energy that gets consumed after finishing the task. Suppose a task is [4, 10]...

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LeetCode 1647 - Minimum Deletions to Make Character Frequencies Unique

LeetCode Problem 1647 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy, Sorting Solution Problem Understanding The problem asks us to make a string good , which means no two distinct characters in the string have the same frequency. The input is a string s consisting of lowercase English letters, and the output is the minimum number of character deletions required to achieve a good string. The frequency of a character...

Practice › Codeforces Solutions › Codeforces Beta Round 96 (Div. 1) ›

CF 132D - Constants in the language of Shakespeare

CF 132D - Constants in the language of Shakespeare Rating: 2100 Tags: constructive algorithms, dp, greedy Solve time: 2m 2s Verified: no Solution Problem Understanding We are asked to represent a positive integer given in binary as a sum of powers of two, with the option of using negative powers, such that the total number of terms is minimized. Formally, we want to write the number as a sum of...

Practice › Codeforces Solutions › Codeforces Beta Round 53 ›

CF 57A - Square Earth?

CF 57A - Square Earth? Rating: 1300 Tags: dfs and similar, greedy, implementation Solve time: 1m 22s Verified: yes Solution Problem Understanding We are asked to find the shortest distance between two points lying on the perimeter of a square of side length n . The square is aligned with the axes, so its corners are at (0,0), (n,0), (0,n), and (n,n). The two points are guaranteed to lie on...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1802 - Maximum Value at a Given Index in a Bounded Array

LeetCode Problem 1802 Difficulty: 🟡 Medium Topics: Math, Binary Search, Greedy Solution LeetCode 1802, Maximum Value at a Given Index in a Bounded Array Problem Understanding This problem asks us to construct an array of length n where every element is a positive integer, the difference between adjacent elements is at most 1 , and the total sum of the array does not exceed maxSum . Among all valid arrays,...

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CF 64C - Table

CF 64C - Table Rating: 1600 Tags: *special, greedy, implementation, math Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given an $n \times m$ table filled with consecutive integers starting from 1. The filling is done row by row, left to right. For example, if $n=3$ and $m=4$, the table looks like this: 1 2 3 4 5 6 7 8 9 10 11 12 Then, the...

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LeetCode 1546 - Maximum Number of Non-Overlapping Subarrays With Sum Equals Target

LeetCode Problem 1546 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Prefix Sum Solution Problem Understanding This problem asks us to find the maximum number of non-overlapping subarrays in a given integer array nums such that the sum of each subarray equals a given target . In simpler terms, we are scanning the array to find consecutive sequences of numbers whose sum matches target and ensuring that no two chosen...

Practice › LeetCode › LeetCode 13xx ›

LeetCode 1383 - Maximum Performance of a Team

LeetCode Problem 1383 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem asks us to build a team of at most k engineers such that the team's performance is maximized. Each engineer has two attributes: speed[i] , representing how fast the engineer is efficiency[i] , representing how efficient the engineer is The performance of a team is defined as: $$\text{performance} = (\text{sum of team...

Practice › LeetCode › LeetCode 12xx ›

LeetCode 1221 - Split a String in Balanced Strings

LeetCode Problem 1221 Difficulty: 🟢 Easy Topics: String, Greedy, Counting Solution LeetCode 1221 - Split a String in Balanced Strings Problem Understanding This problem gives us a string s that contains only the characters 'L' and 'R' . The string is guaranteed to already be balanced overall, meaning the total number of 'L' characters equals the total number of 'R' characters. Our task is to split this string into the...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1733 - Minimum Number of People to Teach

LeetCode Problem 1733 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution Problem Understanding This problem models communication in a social network where each user knows one or more languages. Two users can communicate directly if they share at least one common language. The goal is to ensure that every friendship pair can communicate after teaching exactly one chosen language to some users. The input consists of three parts: n...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1824 - Minimum Sideway Jumps

LeetCode Problem 1824 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding This problem describes a frog navigating a 3-lane road of length n . The frog starts at point 0 in lane 2 and wants to reach point n . Each point along the road may have at most one obstacle in one of the three lanes, represented by the obstacles array. The frog can move forward...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 316 - Remove Duplicate Letters

LeetCode Problem 316 Difficulty: 🟡 Medium Topics: String, Stack, Greedy, Monotonic Stack Solution LeetCode 316, Remove Duplicate Letters Problem Understanding This problem asks us to construct a new string from the input string s such that every distinct character appears exactly once, while also ensuring that the final result is the smallest possible in lexicographical order. The input is a string consisting only of lowercase English letters. Characters may appear...

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Codeforces Beta Round 6 (Div. 2 Only)

Codeforces Beta Round 6 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2600 | Time: 7m 21s Problem Name Rating Tags Solve Time Verified A Triangle 900 brute-force, geometry 1m 18s ✓ B President's Office 1100 implementation 1m 18s ✓ C Alice, Bob and Chocolate 1200 greedy, two-pointers 1m 29s ✓ D Lizards and Basements 2 2600 brute-force, dp 2m 18s ✓ E...

Practice › Codeforces Solutions › Codeforces Beta Round 6 (Div. 2 Only) ›

CF 6C - Alice, Bob and Chocolate

CF 6C - Alice, Bob and Chocolate Rating: 1200 Tags: greedy, two pointers Solve time: 1m 29s Verified: yes Solution Problem Understanding We have a row of chocolate bars, and each bar takes a certain amount of time to eat. Alice starts from the left end and keeps moving right. Bob starts from the right end and keeps moving left. Both eat continuously without pausing, and nobody can partially eat...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2224 - Minimum Number of Operations to Convert Time

LeetCode Problem 2224 Difficulty: 🟢 Easy Topics: String, Greedy Solution Problem Understanding The problem asks us to calculate the minimum number of operations to convert one 24-hour time string, current , into another, correct . Both inputs are formatted as "HH:MM" , where HH is hours from 00 to 23 and MM is minutes from 00 to 59 . Each operation allows us to increase the current time by 1,...

Practice › Codeforces Solutions › Codeforces Beta Round 3 ›

CF 3B - Lorry

CF 3B - Lorry Rating: 1900 Tags: greedy, sortings Solve time: 4m 5s Verified: yes Problem Understanding We have a lorry with capacity v . There are two kinds of boats. A kayak occupies 1 unit of space. A catamaran occupies 2 units of space. Every boat also has a value, its carrying capacity. The goal is to load a subset of boats whose total occupied space does not exceed...

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School Regional Team Contest, Saratov, 2011

School Regional Team Contest, Saratov, 2011 Type: Special | Problems: 10 | Verified: 8/10 | Rating range: 1000-2200 | Time: 16m 31s Problem Name Rating Tags Solve Time Verified A Elevator 1000 brute-force, implementation, math 1m 26s ✓ B Quiz League 1100 implementation 1m 21s ✓ C Winnie-the-Pooh and honey 1100 implementation, math 1m 39s ✓ D Three Sons 1400 brute-force 1m 35s ✓ E Put Knight! 1400 games, math...

Practice › Codeforces Solutions › Codeforces Beta Round 60 ›

CF 65B - Harry Potter and the History of Magic

CF 65B - Harry Potter and the History of Magic Rating: 1700 Tags: brute force, greedy, implementation Solve time: 2m 33s Verified: no Solution Problem Understanding We are given a sequence of four-digit years. Each year may contain mistakes, but we are allowed to repair it by changing at most one digit. After all repairs, the sequence must become non-decreasing, and every resulting year must stay between 1000 and 2011...

Practice › LeetCode › LeetCode 11xx ›

LeetCode 1199 - Minimum Time to Build Blocks

LeetCode Problem 1199 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem requires determining the minimum amount of time to build all blocks using workers that can either build blocks or split into more workers. You are given a list blocks where blocks[i] indicates the time it takes for a worker to complete the i -th block. Initially, there is only one worker, and...

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Codeforces Beta Round 98 (Div. 2)

Codeforces Beta Round 98 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 900-2000 | Time: 7m 45s Problem Name Rating Tags Solve Time Verified A Postcards and photos 900 implementation 1m 28s ✓ B Permutation 1000 greedy 1m 13s ✓ C History 1500 sortings 1m 36s ✓ D Palindromes 1900 dp, strings 2m 9s ✓ E Last Chance 2000 data-structures, implementation, strings 1m 19s...

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LeetCode 1529 - Minimum Suffix Flips

LeetCode Problem 1529 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding This problem is asking us to transform an initial binary string s (all zeros) into a target binary string target using a minimum number of suffix flip operations . A suffix flip operation involves picking an index i and flipping every bit from index i to the end of the string. Flipping a bit means turning '0' to...

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LeetCode 1029 - Two City Scheduling

LeetCode Problem 1029 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding In this problem, we are given an array called costs , where each element represents the travel cost for one person to two different cities. Specifically, costs[i] = [aCosti, bCosti] means: aCosti is the cost of flying person i to city A bCosti is the cost of flying person i to city B There are exactly 2n...

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LeetCode 991 - Broken Calculator

LeetCode Problem 991 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding This problem gives us a calculator that starts with an integer startValue and allows only two operations: Multiply the current number by 2 Subtract 1 Our goal is to transform startValue into target using the minimum number of operations. At first glance, this looks like a shortest path problem where we try different sequences of operations until we...

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LeetCode 807 - Max Increase to Keep City Skyline

LeetCode Problem 807 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding This problem gives us an n x n grid where each cell represents the height of a building in a city. The city can be viewed from four directions: north, south, east, and west. From these viewpoints, the skyline is determined by the tallest building visible in each row or column. When viewing the city from the...

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LeetCode 334 - Increasing Triplet Subsequence

LeetCode Problem 334 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 334 - Increasing Triplet Subsequence Problem Understanding The problem asks us to determine whether an array contains three numbers that form a strictly increasing subsequence. More specifically, we need to find indices i , j , and k such that: i < j < k nums[i] < nums[j] < nums[k] The indices must appear in order, which means we...

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LeetCode 1323 - Maximum 69 Number

LeetCode Problem 1323 Difficulty: 🟢 Easy Topics: Math, Greedy Solution Problem Understanding The problem gives us a positive integer num that contains only the digits 6 and 9 . We are allowed to change at most one digit , where a 6 can become a 9 , or a 9 can become a 6 . Our goal is to return the largest possible number after making zero or one modification....

Practice › LeetCode › LeetCode 01xx ›

LeetCode 134 - Gas Station

LeetCode Problem 134 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem describes a circular route containing n gas stations. At each station i , you can collect gas[i] units of fuel. Traveling from station i to station (i + 1) % n consumes cost[i] units of fuel. You must determine whether there exists a starting station such that a car beginning with an empty tank can complete...

Practice › Codeforces Solutions › Codeforces Beta Round 87 (Div. 2 Only) ›

CF 116B - Little Pigs and Wolves

CF 116B - Little Pigs and Wolves Rating: 1100 Tags: greedy, implementation Solve time: 2m 30s Verified: yes Solution Problem Understanding We have a small rectangular grid where each cell is either empty, contains a pig, or contains a wolf. A wolf may eat one pig that is directly adjacent to it in one of the four cardinal directions. Once a pig is eaten, it disappears and cannot be eaten...

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LeetCode 410 - Split Array Largest Sum

LeetCode Problem 410 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Greedy, Prefix Sum Solution Problem Understanding The problem gives an integer array nums and an integer k . We must divide the array into exactly k non-empty contiguous subarrays. Among those subarrays, each one has its own sum, and the goal is to minimize the largest subarray sum. In other words, we are trying to split the array...

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LeetCode 763 - Partition Labels

LeetCode Problem 763 Difficulty: 🟡 Medium Topics: Hash Table, Two Pointers, String, Greedy Solution Problem Understanding The problem is asking us to partition a string s into as many contiguous parts as possible such that no letter appears in more than one part. In other words, each character in the string should be confined to a single segment. After partitioning, concatenating all the segments in order should reproduce the original...

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Codeforces Beta Round 68

Codeforces Beta Round 68 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2800 | Time: 22m 53s Problem Name Rating Tags Solve Time Verified A Room Leader 1000 implementation 1m 35s ✓ B Train 1500 dp, games, greedy 2m 11s ✓ C Chessboard Billiard 2100 dfs-and-similar, dsu, graphs 1m 36s ✓ D Hanger 2400 data-structures 1m 7s ✓ E Shift It! 2800 constructive-algorithms 16m 24s ✗

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LeetCode 1090 - Largest Values From Labels

LeetCode Problem 1090 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Counting Solution Problem Understanding The problem gives us two arrays, values and labels , where each index represents a single item. The item at index i has a value values[i] and a category or group identifier labels[i] . We want to choose a subset of these items such that two constraints are satisfied: We can select at most...

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LeetCode 1833 - Maximum Ice Cream Bars

LeetCode Problem 1833 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Counting Sort Solution Problem Understanding This problem asks us to determine the maximum number of ice cream bars a boy can buy with a limited number of coins. The input consists of an array costs , where costs[i] represents the price of the i-th ice cream bar, and an integer coins representing the total coins available. The boy can purchase...

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LeetCode 1526 - Minimum Number of Increments on Subarrays to Form a Target Array

LeetCode Problem 1526 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem gives us a target array and asks us to build it starting from an array of all zeros. The only operation allowed is selecting any contiguous subarray and incrementing every element in that subarray by exactly one. The goal is to determine the minimum number of such operations required to transform...

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LeetCode 611 - Valid Triangle Number

LeetCode Problem 611 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding The problem asks us to determine how many triplets from a given integer array nums can form a valid triangle. In geometric terms, a triangle is valid if the sum of any two sides is greater than the third side. Because we are only concerned with side lengths from an array, the key...

Practice › Codeforces Solutions › Yandex.Algorithm 2011: Round 2 ›

CF 86B - Tetris revisited

CF 86B - Tetris revisited Rating: 2200 Tags: constructive algorithms, graph matchings, greedy, math Solve time: 2m 5s Verified: yes Solution Problem Understanding We have a rectangular board where some cells are already blocked by # and the remaining cells . must be covered by polyominoes. The allowed pieces are extremely flexible: any connected shape consisting of 2, 3, 4, or 5 cells may be used, with arbitrary rotations and...

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LeetCode 649 - Dota2 Senate

LeetCode Problem 649 Difficulty: 🟡 Medium Topics: String, Greedy, Queue Solution Problem Understanding The problem describes a turn-based voting process between two parties in the Dota2 senate, the Radiant party represented by 'R' and the Dire party represented by 'D' . We are given a string senate where each character represents a senator and their party affiliation. The order of characters in the string is important because senators act sequentially...

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LeetCode 2233 - Maximum Product After K Increments

LeetCode Problem 2233 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to maximize the product of an array of non-negative integers after performing at most k increment operations, where each operation increases any single element by 1 . In other words, given an array nums and an integer k , we want to distribute these k increments across the elements of nums...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 1) ›

CF 135C - Zero-One

CF 135C - Zero-One Rating: 1900 Tags: constructive algorithms, games, greedy Solve time: 1m 50s Verified: yes Solution Problem Understanding We are given a string consisting of 0 , 1 , and ? . Each character represents a card in a row. During the game, players alternately remove one card until only two cards remain. Masha moves first and wants the final two-bit binary number to be as small as...

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LeetCode 871 - Minimum Number of Refueling Stops

LeetCode Problem 871 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem describes a car traveling from position 0 to a destination located target miles away. The car starts with startFuel liters of fuel, and every mile driven consumes exactly one liter of fuel. Along the route, there are gas stations positioned at increasing distances from the start. Each gas station is represented...

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School Team Contest 1 (Winter Computer School 2010/11)

School Team Contest 1 (Winter Computer School 2010/11) Type: Special | Problems: 11 | Verified: 9/11 | Rating range: 1100-2600 | Time: 23m 20s Problem Name Rating Tags Solve Time Verified A C*++ Calculations 2000 expression-parsing, greedy 2m 42s ✓ B Company Income Growth 1300 greedy 3m 27s ✓ C Moon Craters 2100 dp, sortings 4m 25s ✗ D Cubical Planet 1100 math 1m 27s ✓ E What Has Dirichlet...

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LeetCode 1605 - Find Valid Matrix Given Row and Column Sums

LeetCode Problem 1605 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives us two arrays: rowSum , where rowSum[i] represents the total sum required for row i colSum , where colSum[j] represents the total sum required for column j Our task is to construct any matrix of non-negative integers such that: Every row adds up to its corresponding value in rowSum Every column adds up to...

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Codeforces Beta Round 19

Codeforces Beta Round 19 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1400-2900 | Time: 16m 37s Problem Name Rating Tags Solve Time Verified A World Football Cup 1400 implementation 5m 51s ✓ B Checkout Assistant 1900 dp 3m 5s ✓ C Deletion of Repeats 2200 greedy, hashing, string-suffix-structures 2m 2s ✓ D Points 2800 data-structures 3m 49s ✓ E Fairy 2900 dfs-and-similar, divide-and-conquer, dsu 1m 50s...

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LeetCode 659 - Split Array into Consecutive Subsequences

LeetCode Problem 659 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us a sorted integer array nums , and asks whether we can divide every element into one or more subsequences that satisfy two conditions. First, each subsequence must consist of consecutive increasing integers. This means every next value must be exactly 1 larger than the previous value. For example, [3,4,5]...

Practice › Codeforces Solutions › Codeforces Beta Round 33 (Codeforces format) ›

CF 33C - Wonderful Randomized Sum

CF 33C - Wonderful Randomized Sum Rating: 1800 Tags: greedy Solve time: 3m 6s Verified: yes Solution Problem Understanding We are given a sequence of integers, and the task is to maximize its sum by performing two operations: first, we may choose any prefix of the sequence and multiply every element in it by -1; second, we may choose any suffix of the sequence and multiply every element in it...

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School Team Contest 3 (Winter Computer School 2010/11)

School Team Contest 3 (Winter Computer School 2010/11) Type: Special | Problems: 10 | Verified: 7/10 | Rating range: 900-2500 | Time: 19m 28s Problem Name Rating Tags Solve Time Verified A Codecraft III 900 implementation 1m 14s ✓ B School 2200 dp, dsu 2m 6s ✓ C Dancing Lessons 1900 data-structures 1m 24s ✓ D Event Dates 1900 greedy, meet-in-the-middle, sortings 1m 35s ✓ E Director 2000 constructive-algorithms, greedy...

Practice › Codeforces Solutions › Codeforces Beta Round 63 (Div. 2) ›

CF 69B - Bets

CF 69B - Bets Rating: 1200 Tags: greedy, implementation Solve time: 2m 1s Verified: yes Solution Problem Understanding Each athlete runs through a contiguous interval of sections. While an athlete is inside a section, they spend exactly t[i] time on that section, so the winner of a section is simply the active athlete with the smallest t . If several athletes have the same time, the smaller index wins. We...

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LeetCode 1675 - Minimize Deviation in Array

LeetCode Problem 1675 Difficulty: 🔴 Hard Topics: Array, Greedy, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to minimize the deviation in an array of positive integers. The deviation is defined as the difference between the maximum and minimum elements in the array. We can modify the array using two operations: if an element is even, we can divide it by 2, and if an element...

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CF 64D - Presents

CF 64D - Presents Rating: 1800 Tags: *special, greedy Solve time: 1m 40s Verified: yes Solution Problem Understanding We are given three positive integers representing the prices of three presents. There are three sisters, ranked by age: eldest, middle, and youngest. The task is to assign each present to a sister according to the rule that the most expensive present goes to the eldest sister, the second most expensive to...

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LeetCode 1388 - Pizza With 3n Slices

LeetCode Problem 1388 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Heap (Priority Queue) Solution Problem Understanding In this problem, we are given a circular pizza divided into 3n slices. Each slice has a size represented by the array slices , where the values are listed in clockwise order. You repeatedly perform the following process: You choose any remaining slice. Alice immediately takes the slice directly anti-clockwise from your chosen...

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LeetCode 826 - Most Profit Assigning Work

LeetCode Problem 826 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding This problem asks us to maximize the total profit earned by assigning jobs to workers, under a specific rule: each worker can only perform jobs whose difficulty is less than or equal to their ability. We are given three arrays: difficulty[i] represents how difficult the i-th job is. profit[i] represents how much money...

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CF 16B - Burglar and Matches

CF 16B - Burglar and Matches Rating: 900 Tags: greedy, implementation, sortings Solve time: 1m 13s Verified: yes Solution Problem Understanding We have a burglar who can carry exactly n matchboxes. In the warehouse, there are m containers. Each container i has a_i matchboxes, and every matchbox in that container contains b_i matches. The goal is to pick up to n matchboxes such that the total number of matches is...

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LeetCode 1585 - Check If String Is Transformable With Substring Sort Operations

LeetCode Problem 1585 Difficulty: 🔴 Hard Topics: String, Greedy, Sorting Solution Problem Understanding This problem asks whether we can transform one digit string, s , into another digit string, t , using a special operation. In one operation, we choose any non-empty contiguous substring of s and sort that substring in ascending order. The important detail is that sorting a substring only moves smaller digits toward the left and larger...

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Unknown Language Round 2

Unknown Language Round 2 Type: Special | Problems: 9 | Verified: 8/9 | Rating range: 1000-2300 | Time: 21m 37s Problem Name Rating Tags Solve Time Verified A Goshtasp, Vishtasp and Eidi 1800 *special, greedy, math 1m 18s ✓ B INI-file 2200 *special, implementation 1m 45s ✓ C Extraordinarily Nice Numbers 1200 *special, math 1m 26s ✓ D Perse-script 2300 *special, expression-parsing 1m 55s ✗ E Ali goes shopping 1800...

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CF 59D - Team Arrangement

CF 59D - Team Arrangement Rating: 2000 Tags: constructive algorithms, greedy, implementation Solve time: 2m 39s Verified: no Solution Problem Understanding We have 3n students ranked by personal performance. Higher-ranked students become captains earlier. When a captain forms a team, they choose two currently unassigned students according to their personal preference list. The final teams are already known, and the teams are listed in the exact order they were created....

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CF 3A - Shortest path of the king

CF 3A - Shortest path of the king Rating: 1000 Tags: greedy, shortest paths Solve time: 4m 37s Verified: yes Problem Understanding We are asked to move a chess king from one square to another on a standard 8×8 board in the fewest number of moves. The king can move to any adjacent square in eight possible directions: vertically, horizontally, or diagonally. The input specifies the start and target squares...

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LeetCode 1689 - Partitioning Into Minimum Number Of Deci-Binary Numbers

LeetCode Problem 1689 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding The problem asks us to determine the minimum number of positive deci-binary numbers required to sum up to a given decimal number represented as a string. A deci-binary number is a number whose digits consist only of 0 and 1 , and it cannot contain leading zeros. For example: 101 is valid because every digit is either 0...

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LeetCode 1262 - Greatest Sum Divisible by Three

LeetCode Problem 1262 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem asks us to find the maximum sum of elements from an integer array nums such that the sum is divisible by three. In other words, we are allowed to pick any subset of numbers from the array, and our goal is to maximize the sum of that subset under the condition that the...

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CF 72F - Oil

CF 72F - Oil Rating: 1900 Tags: *special, greedy, math Solve time: 1m 43s Verified: yes Solution Problem Understanding We have an n × m grid. Some entire rows are empty, some entire columns are empty, and every empty cell belongs to at least one of those empty rows or empty columns. All remaining cells contain oil. If we drill a well in one oil cell, we can reach every...

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Manthan 2011

Manthan 2011 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1800-2600 | Time: 9m 26s Problem Name Rating Tags Solve Time Verified A Partial Teacher 1800 dp, graphs, greedy 2m 6s ✓ B Restoration of the Permutation 1800 greedy 1m 59s ✓ C Sequence of Balls 2600 dp 1m 24s ✓ D Optical Experiment 1900 binary-search, data-structures, dp 1m 53s ✓ E Save the City! 2500 geometry...

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Codeforces Beta Round 42 (Div. 2)

Codeforces Beta Round 42 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2300 | Time: 9m 18s Problem Name Rating Tags Solve Time Verified A Football 1000 strings 1m 29s ✓ B Letter 1100 implementation, strings 1m 31s ✓ C Lucky Tickets 1300 greedy 1m 12s ✓ D Journey 2000 brute-force, constructive-algorithms, implementation 1m 39s ✓ E Race 2300 brute-force, implementation, two-pointers 3m 27s...

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CF 51C - Three Base Stations

CF 51C - Three Base Stations Rating: 1800 Tags: binary search, greedy Solve time: 2m 13s Verified: no Solution Problem Understanding We are given a village represented as points along a one-dimensional line, each point being a house coordinate. The task is to place exactly three cellular base stations along this line so that every house lies within the coverage of at least one station. Coverage is symmetric: a station...

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LeetCode 376 - Wiggle Subsequence

LeetCode Problem 376 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem asks us to find the length of the longest subsequence in an array such that the differences between consecutive elements alternate between positive and negative. A wiggle sequence follows a strict alternating pattern: Positive difference, then negative difference, then positive again Or negative difference, then positive difference, then negative again The actual values do...

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CF 67A - Partial Teacher

CF 67A - Partial Teacher Rating: 1800 Tags: dp, graphs, greedy, implementation Solve time: 2m 6s Verified: yes Solution Problem Understanding We have a line of students, and for every adjacent pair we know only the relative order of their marks. If the relation character between positions i and i + 1 is: L , then student i must receive strictly more toffees than student i + 1 R ,...

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LeetCode 1328 - Break a Palindrome

LeetCode Problem 1328 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding The problem asks us to modify a given palindromic string in such a way that it is no longer a palindrome while ensuring that the resulting string is the lexicographically smallest possible. A palindrome is a string that reads the same forwards and backwards. In this problem, the input palindrome consists only of lowercase English letters and has...

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Codeforces Beta Round 60

Codeforces Beta Round 60 Type: Beta | Problems: 5 | Verified: 3/5 | Rating range: 1700-2900 | Time: 11m 31s Problem Name Rating Tags Solve Time Verified A Harry Potter and Three Spells 1800 implementation, math 2m 2s ✓ B Harry Potter and the History of Magic 1700 brute-force, greedy, implementation 2m 33s ✗ C Harry Potter and the Golden Snitch 2100 binary-search, geometry 2m 11s ✓ D Harry Potter...

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LeetCode 1007 - Minimum Domino Rotations For Equal Row

LeetCode Problem 1007 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us two arrays, tops and bottoms , representing a sequence of dominoes. Each domino has two values, one on the top half and one on the bottom half. For the i th domino, the top value is tops[i] and the bottom value is bottoms[i] . We are allowed to rotate any domino individually. Rotating a...

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CF 73D - FreeDiv

CF 73D - FreeDiv Rating: 2200 Tags: dfs and similar, graphs, greedy Solve time: 2m 38s Verified: yes Solution Problem Understanding We are given an undirected graph where cities are vertices and roads are edges. Each connected component of the graph is called a province. Vasya may additionally build tunnels between cities, but tunnels have two restrictions. First, every city can participate in at most one tunnel. Second, every province...

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LeetCode 2037 - Minimum Number of Moves to Seat Everyone

LeetCode Problem 2037 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Counting Sort Solution Problem Understanding This problem asks us to assign students to seats such that every student occupies exactly one seat and no two students share the same seat. Each student can move left or right on a number line, and every movement by one position costs exactly one move. The goal is to minimize the total number of...

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LeetCode 1713 - Minimum Operations to Make a Subsequence

LeetCode Problem 1713 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Greedy Solution LeetCode 1713, Minimum Operations to Make a Subsequence Problem Understanding The problem gives us two arrays, target and arr . The target array contains distinct integers, which is extremely important. The arr array may contain duplicates. We are allowed to perform insert operations on arr . In a single operation, we can insert any integer at...

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Codeforces Beta Round 4 (Div. 2 Only)

Codeforces Beta Round 4 (Div. 2 Only) Type: Div. 2 | Problems: 4 | Verified: 4/4 | Rating range: 800-1700 | Time: 4m 57s Problem Name Rating Tags Solve Time Verified A Watermelon 800 brute-force, math 46s ✓ B Before an Exam 1200 constructive-algorithms, greedy 1m 12s ✓ C Registration System 1300 data-structures, hashing, implementation 1m 42s ✓ D Mysterious Present 1700 dp, sortings 1m 17s ✓

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LeetCode 55 - Jump Game

LeetCode Problem 55 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution LeetCode 55 - Jump Game Problem Understanding The problem gives us an integer array nums , where each value represents the maximum distance we are allowed to jump forward from that position. You always start at index 0 . From index i , you may jump any distance between 1 and nums[i] , as long as you stay...

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LeetCode 321 - Create Maximum Number

LeetCode Problem 321 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Stack, Greedy, Monotonic Stack Solution LeetCode 321 - Create Maximum Number Problem Understanding This problem asks us to build the lexicographically largest possible number of length k using digits taken from two arrays, nums1 and nums2 . Each array represents a sequence of digits from a number. We are allowed to choose some digits from nums1 and some digits from...

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LeetCode 1247 - Minimum Swaps to Make Strings Equal

LeetCode Problem 1247 Difficulty: 🟡 Medium Topics: Math, String, Greedy Solution Problem Understanding This problem asks us to determine the minimum number of swaps needed to make two strings, s1 and s2 , equal. Both strings are of the same length and consist only of the characters "x" and "y" . The allowed swap operation is restricted: you may only swap characters between the two strings, not within the same...

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CF 95B - Lucky Numbers

CF 95B - Lucky Numbers Rating: 1800 Tags: dp, greedy Solve time: 1m 52s Verified: yes Solution Problem Understanding We need to construct the smallest number that is at least n and satisfies two conditions simultaneously. Every digit must be either 4 or 7 , and the total count of 4 s must equal the total count of 7 s. The input is a decimal string that can be extremely...

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LeetCode 870 - Advantage Shuffle

LeetCode Problem 870 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem asks us to maximize the advantage of one array over another . Given two arrays nums1 and nums2 of equal length, the advantage is defined as the number of positions i where nums1[i] > nums2[i] . Our task is to rearrange nums1 to maximize this advantage. The input arrays represent two sets of...

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LeetCode 1717 - Maximum Score From Removing Substrings

LeetCode Problem 1717 Difficulty: 🟡 Medium Topics: String, Stack, Greedy Solution Problem Understanding The problem gives us a string s and two scoring rules: Removing the substring "ab" earns x points. Removing the substring "ba" earns y points. We may perform these removals as many times as possible, in any order we choose. Every time we remove a substring, the remaining characters close together, which may create new removable substrings....

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LeetCode 1703 - Minimum Adjacent Swaps for K Consecutive Ones

LeetCode Problem 1703 Difficulty: 🔴 Hard Topics: Array, Greedy, Sliding Window, Prefix Sum Solution Problem Understanding This problem asks us to determine the minimum number of adjacent swaps needed to make exactly k ones appear consecutively in a binary array. The input array nums contains only 0 and 1 . In one operation, we may swap two neighboring elements. Since swaps are adjacent only, moving a 1 from index i...

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LeetCode 324 - Wiggle Sort II

LeetCode Problem 324 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Greedy, Sorting, Quickselect Solution Problem Understanding The problem asks us to rearrange an array so that it follows a strict alternating pattern: nums[0] < nums[1] nums[1] > nums[2] nums[2] < nums[3] and so on. This pattern is called a wiggle sequence because the values repeatedly go up and down. The input is an integer array nums , and we...

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CF 111A - Petya and Inequiations

CF 111A - Petya and Inequiations Rating: 1400 Tags: greedy Solve time: 2m 33s Verified: no Solution Problem Understanding We need to construct an array of n positive integers. The array must satisfy two conditions at the same time. The sum of squares of all elements must be at least x , while the ordinary sum of the elements must not exceed y . The task is not to optimize...

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LeetCode 1005 - Maximize Sum Of Array After K Negations

LeetCode Problem 1005 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem is asking us to maximize the sum of an integer array after performing exactly k negations. A negation operation consists of picking an index i and replacing nums[i] with -nums[i] . This operation can be applied to the same element multiple times. The input consists of an array of integers nums and an integer k...

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CF 85B - Embassy Queue

CF 85B - Embassy Queue Rating: 1800 Tags: data structures, greedy Solve time: 2m 1s Verified: yes Solution Problem Understanding Each person visiting the embassy must pass through three consecutive stages. The first stage has k1 identical windows, each service taking t1 time. The second stage has k2 windows with service time t2 , and the third stage has k3 windows with service time t3 . Person i arrives at...

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LeetCode 1488 - Avoid Flood in The City

LeetCode Problem 1488 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to simulate rainfall over a series of lakes and prevent flooding. Each day is represented by an integer in the rains array. If rains[i] > 0 , it means lake rains[i] receives rain and becomes full. If it is already full, it floods, which we must avoid....

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LeetCode 280 - Wiggle Sort

LeetCode Problem 280 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to rearrange an integer array so that it follows a specific alternating pattern called a wiggle sequence. The required relationship is: nums[0] <= nums[1] nums[1] >= nums[2] nums[2] <= nums[3] nums[3] >= nums[4] and so on. In other words, the values should alternate between valleys and peaks. Elements at odd indices should be...

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LeetCode 621 - Task Scheduler

LeetCode Problem 621 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting Solution Problem Understanding The Task Scheduler problem asks us to determine the minimum number of CPU intervals required to complete a list of tasks with a cooling constraint. Each task is represented by an uppercase letter A-Z. The CPU can execute one task per interval or remain idle. After executing a task, the CPU...

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LeetCode 1282 - Group the People Given the Group Size They Belong To

LeetCode Problem 1282 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution Problem Understanding The problem gives us an array called groupSizes , where each index represents a person and each value represents the size of the group that person must belong to. Every person has a unique ID ranging from 0 to n - 1 , where n is the length of the array. For any person i ,...

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CF 39A - C*++ Calculations

CF 39A - C*++ Calculations Rating: 2000 Tags: expression parsing, greedy Solve time: 2m 42s Verified: yes Solution Problem Understanding We are given an arithmetic expression built from terms involving a single variable a . Every term is one of two forms: k * a++ k * ++a where k is an integer coefficient between 0 and 1000 . If the coefficient is missing, it is treated as 1 ....

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CF 91D - Grocer's Problem

CF 91D - Grocer's Problem Rating: 2600 Tags: constructive algorithms, graphs, greedy Solve time: 2m 25s Verified: yes Solution Problem Understanding We are given a permutation of jars. Jar i should finally stand at position i , but the current arrangement is shuffled. One operation allows us to choose any subset of at most five positions and permute the jars inside those positions arbitrarily. The positions do not need to...

Practice › Codeforces Solutions › School Team Contest 3 (Winter Computer School 2010/11) ›

CF 45F - Goats and Wolves

CF 45F - Goats and Wolves Rating: 2500 Tags: greedy Solve time: 2m 25s Verified: yes Solution Problem Understanding We have the classical river crossing setting, but with a precise safety rule that changes how transitions work. Initially, there are m goats and m wolves on the left bank. The goal is to move all animals to the right bank using a boat that can carry at most n animals...

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CF 62A - A Student's Dream

CF 62A - A Student's Dream Rating: 1300 Tags: greedy, math Solve time: 1m 13s Verified: yes Solution Problem Understanding We have four integers describing the number of fingers on two alien hands. The Venusian girl has al fingers on her left hand and ar on her right hand. The Marsian boy has bl and br fingers. They want to hold exactly one pair of hands. Since either person may...

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LeetCode 1794 - Count Pairs of Equal Substrings With Minimum Difference

LeetCode Problem 1794 Difficulty: 🟡 Medium Topics: Hash Table, String, Greedy Solution Problem Understanding This problem asks us to count quadruples of indices (i, j, a, b) where substrings from two given strings are equal and the difference j - a is minimized. Specifically, i and j define a substring in firstString , while a and b define a substring in secondString . The substrings themselves must be identical, and...

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LeetCode 910 - Smallest Range II

LeetCode Problem 910 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting Solution LeetCode 910, Smallest Range II Problem Understanding The problem gives us an integer array nums and an integer k . For every element in the array, we must choose exactly one of two operations: add k subtract k After modifying every element, we calculate the score of the array, which is defined as: max(nums) - min(nums) Our goal...

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LeetCode 1727 - Largest Submatrix With Rearrangements

LeetCode Problem 1727 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Matrix Solution Problem Understanding The problem gives us a binary matrix, meaning every cell contains either 0 or 1 . We are allowed to rearrange the columns of the matrix in any order we want. The rearrangement is global for the row configuration being considered, meaning we are effectively free to permute the columns to maximize the size of a...

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LeetCode 1642 - Furthest Building You Can Reach

LeetCode Problem 1642 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array heights , where each value represents the height of a building. You start at building 0 and attempt to move sequentially to the right, one building at a time. When moving from building i to building i+1 , there are two possibilities: If the next building is shorter or...

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Codeforces Beta Round 74 (Div. 2 Only)

Codeforces Beta Round 74 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 1000-1100 | Time: 3m 17s Problem Name Rating Tags Solve Time Verified A Cableway 1000 greedy, math 1m 33s ✓ B African Crossword 1100 implementation, strings 1m 44s ✓

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LeetCode 435 - Non-overlapping Intervals

LeetCode Problem 435 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem gives an array of intervals where each interval is represented as [start, end] . Each interval describes a continuous range on a number line. The task is to remove the minimum number of intervals so that the remaining intervals no longer overlap. Two intervals overlap if one starts before the other finishes. However,...

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LeetCode 1353 - Maximum Number of Events That Can Be Attended

LeetCode Problem 1353 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us a list of events, where each event is represented as a pair [startDay, endDay] . An event is available to attend on any single day within that inclusive range. The goal is to attend as many events as possible, with the restriction that only one event can be attended per...

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LeetCode 1541 - Minimum Insertions to Balance a Parentheses String

LeetCode Problem 1541 Difficulty: 🟡 Medium Topics: String, Stack, Greedy Solution Problem Understanding This problem asks us to transform a string of parentheses into a special kind of balanced parentheses string using the minimum number of insertions. Unlike the standard parentheses balancing problem, this problem defines balance differently. Every opening parenthesis '(' must be matched with exactly two consecutive closing parentheses '))' . That means: One '(' requires two ')'...

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CF 3D - Least Cost Bracket Sequence

CF 3D - Least Cost Bracket Sequence Rating: 2600 Tags: greedy Solve time: 1m 23s Verified: yes Problem Understanding We are given a bracket string containing three kinds of characters: '(' , ')' , and '?' . Every '?' must eventually become either an opening or closing bracket. For each unknown position, the input provides two costs, one for replacing it with '(' and one for replacing it with ')'...

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Codeforces Beta Round 75 (Div. 2 Only)

Codeforces Beta Round 75 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1300 | Time: 4m 34s Problem Name Rating Tags Solve Time Verified A Chips 800 implementation, math 3m 15s ✓ B Binary Number 1300 greedy 1m 19s ✓

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LeetCode 1081 - Smallest Subsequence of Distinct Characters

LeetCode Problem 1081 Difficulty: 🟡 Medium Topics: String, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to construct the lexicographically smallest subsequence of a string that contains every distinct character exactly once. A subsequence is formed by deleting zero or more characters without changing the relative order of the remaining characters. This is important because we are not allowed to rearrange characters arbitrarily. The final answer must...

Practice › Codeforces Solutions › School Team Contest 3 (Winter Computer School 2010/11) ›

CF 45D - Event Dates

CF 45D - Event Dates Rating: 1900 Tags: greedy, meet-in-the-middle, sortings Solve time: 1m 35s Verified: yes Solution Problem Understanding Each event has a range of possible days when it could have happened. For the $i$-th event, any integer day between $l_i$ and $r_i$ is acceptable. We must assign exactly one day to every event, and no two events may share the same day. The task is not to count...

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LeetCode 402 - Remove K Digits

LeetCode Problem 402 Difficulty: 🟡 Medium Topics: String, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem gives us a numeric string num and an integer k . We must remove exactly k digits from the number so that the resulting integer is as small as possible. The key detail is that we are not allowed to reorder digits. We may only delete digits while preserving the relative order of...

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LeetCode 1433 - Check If a String Can Break Another String

LeetCode Problem 1433 Difficulty: 🟡 Medium Topics: String, Greedy, Sorting Solution Problem Understanding The problem asks us to determine whether one string can "break" another string through some permutation. Given two strings s1 and s2 of equal length, a string x can break string y if, after arranging both strings in some order, every character in x is greater than or equal to the corresponding character in y when compared...

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CF 101A - Homework

CF 101A - Homework Rating: 1200 Tags: greedy Solve time: 2m 5s Verified: yes Solution Problem Understanding We start with a lowercase string and may delete at most k characters from it. The remaining characters must stay in their original order, since deleting characters creates a subsequence. Our goal is not to maximize the remaining length, but to minimize how many distinct letters still appear. If a letter appears even...

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Codeforces Testing Round 2

Codeforces Testing Round 2 Type: Special | Problems: 3 | Verified: 2/3 | Rating range: 1000-1600 | Time: 5m 4s Problem Name Rating Tags Solve Time Verified A Measuring Lengths in Baden 1400 math 1m 18s ✓ B Simple XML 1000 implementation 1m 41s ✓ C Hobbits' Party 1600 constructive-algorithms, greedy 2m 5s ✗

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Codeforces Beta Round 37

Codeforces Beta Round 37 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2600 | Time: 8m 37s Problem Name Rating Tags Solve Time Verified A Towers 1000 sortings 53s ✓ B Computer Game 1800 greedy, implementation 1m 56s ✓ C Old Berland Language 1900 data-structures, greedy, trees 1m 42s ✓ D Lesson Timetable 2300 combinatorics, dp, math 2m 23s ✗ E Trial for Chief 2600 graphs, greedy,...

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CF 70B - Text Messaging

CF 70B - Text Messaging Rating: 1600 Tags: expression parsing, greedy, strings Solve time: 1m 39s Verified: yes Solution Problem Understanding We are given the maximum length of a single SMS message and one complete text consisting of sentences separated by spaces. A sentence always ends with one of . , ? , or ! . Words contain only letters. The task is to split the text into the minimum...

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LeetCode 122 - Best Time to Buy and Sell Stock II

LeetCode Problem 122 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding This problem asks us to maximize profit from stock trading over a sequence of days. We are given an array prices , where prices[i] represents the stock price on the i th day. We are allowed to perform as many buy and sell transactions as we want, with one important restriction: at any moment, we can...

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CF 73B - Need For Brake

CF 73B - Need For Brake Rating: 2000 Tags: binary search, greedy, sortings Solve time: 2m 9s Verified: yes Solution Problem Understanding We know the current championship standings before the final race. Every racer already has some number of points, and the last race distributes additional points to the top m finishers. The racer in first place of the race receives b[0] points, the racer in second place receives b[1]...

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CF 37C - Old Berland Language

CF 37C - Old Berland Language Rating: 1900 Tags: data structures, greedy, trees Solve time: 1m 42s Verified: yes Solution Problem Understanding We need to construct a binary prefix code. The input gives the lengths of all words in the language. Every word may contain only 0 and 1 , and no word is allowed to be the prefix of another. We must either build such a set of words...

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LeetCode 768 - Max Chunks To Make Sorted II

LeetCode Problem 768 Difficulty: 🔴 Hard Topics: Array, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding The problem asks us to partition an array into the maximum possible number of contiguous chunks such that, after sorting each chunk independently and concatenating the results, the entire array becomes globally sorted. The key detail is that each chunk must remain contiguous. We cannot rearrange elements across chunk boundaries after splitting. Once the...

Practice › Codeforces Solutions › Codeforces Beta Round 35 (Div. 2) ›

CF 35D - Animals

CF 35D - Animals Rating: 1700 Tags: dp, greedy Solve time: 1m 14s Verified: yes Solution Problem Understanding We are asked to simulate a farm in which animals arrive one per day over n days. Each animal has a fixed daily food requirement starting from the day it arrives. The farm starts with X tons of food. Every day we can either accept or reject the arriving animal, but we...

Practice › Codeforces Solutions › Codeforces Beta Round 54 (Div. 2) ›

CF 58A - Chat room

CF 58A - Chat room Rating: 1000 Tags: greedy, strings Solve time: 1m 20s Verified: yes Solution Problem Understanding The problem asks whether Vasya, who typed a string of lowercase letters, effectively managed to say "hello". The goal is not to check if the typed string is exactly "hello", but whether we can remove some letters (possibly zero) to produce the sequence h , e , l , l ,...

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LeetCode 630 - Course Schedule III

LeetCode Problem 630 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives a list of online courses, where each course is represented as [duration, lastDay] . The duration tells us how many consecutive days are required to complete the course. The lastDay tells us the latest possible day by which the course must be finished. You begin on day 1 , and only...

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LeetCode 624 - Maximum Distance in Arrays

LeetCode Problem 624 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem presents a list of m arrays, each individually sorted in ascending order. You are asked to pick one element from two different arrays and compute the absolute difference between these two elements, which is defined as the distance. The goal is to find the maximum possible distance between any such pair. The input represents multiple arrays...

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LeetCode 1580 - Put Boxes Into the Warehouse II

LeetCode Problem 1580 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding In this problem, we are given two arrays: boxes , where each value represents the height of a box warehouse , where each value represents the height of a room in the warehouse Every box has width 1 , and every warehouse room also has width 1 . Boxes cannot be stacked, meaning each room can contain...

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LeetCode 1838 - Frequency of the Most Frequent Element

LeetCode Problem 1838 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sliding Window, Sorting, Prefix Sum Solution Problem Understanding This problem asks us to determine the maximum frequency of an element in an integer array nums after performing at most k increment operations. Each operation allows you to choose an element and increase it by 1 . The frequency of an element is the number of times it occurs in...

Practice › Codeforces Solutions › Codeforces Beta Round 66 ›

CF 73A - The Elder Trolls IV: Oblivon

CF 73A - The Elder Trolls IV: Oblivon Rating: 1600 Tags: greedy, math Solve time: 1m 48s Verified: yes Solution Problem Understanding We have a rectangular block made of unit cubes with dimensions x × y × z . A single cut is always made along the grid lines and must be parallel to one of the faces of the box. Since the cuts are infinitely long and the pieces...

Practice › Codeforces Solutions › Codeforces Beta Round 80 (Div. 1 Only) ›

CF 103C - Russian Roulette

CF 103C - Russian Roulette Rating: 1900 Tags: constructive algorithms, greedy Solve time: 2m Verified: yes Solution Problem Understanding The cylinder has n slots arranged in a circle, and exactly k of them contain bullets. Before the game starts, the cylinder is rotated uniformly at random, so every cyclic shift is equally likely. After the rotation, Sasha shoots first. If the current slot is empty, the cylinder advances by one...

Practice › Codeforces Solutions › Codeforces Beta Round 79 (Div. 1 Only) ›

CF 101D - Castle

CF 101D - Castle Rating: 2300 Tags: dp, greedy, probabilities, sortings, trees Solve time: 2m 6s Verified: yes Solution Problem Understanding We are given a weighted tree rooted at hall 1, where Gerald starts. The treasure is hidden uniformly at random in one of the other halls. Gerald only discovers the treasure when he first enters the correct hall. The restriction that changes the problem completely is that every corridor...

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LeetCode 1536 - Minimum Swaps to Arrange a Binary Grid

LeetCode Problem 1536 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives us an n x n binary matrix called grid . Each cell contains either 0 or 1 . We are allowed to perform operations where we swap two adjacent rows. The goal is to transform the matrix into a valid configuration using the minimum number of adjacent row swaps. A grid is considered valid...

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Codeforces Beta Round 85 (Div. 1 Only)

Codeforces Beta Round 85 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1400-2900 | Time: 12m 59s Problem Name Rating Tags Solve Time Verified A Petya and Inequiations 1400 greedy 2m 33s ✗ B Petya and Divisors 1900 binary-search, data-structures, number-theory 2m 50s ✓ C Petya and Spiders 2100 bitmasks, dp, dsu 2m 34s ✓ D Petya and Coloring 2300 combinatorics, dp 2m...

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LeetCode 502 - IPO

LeetCode Problem 502 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem describes a scenario where we have a limited number of opportunities to invest in projects before an IPO. Each project has two properties: profits[i] , the amount of capital gained after completing the project capital[i] , the minimum amount of capital required to start the project We are also given: k ,...

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LeetCode 1564 - Put Boxes Into the Warehouse I

LeetCode Problem 1564 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us two arrays: boxes , where each value represents the height of a box warehouse , where each value represents the height of a room in the warehouse Every box has width 1 , and every warehouse room also has width 1 . Boxes cannot be stacked, so each room can hold at most...

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LeetCode 1144 - Decrease Elements To Make Array Zigzag

LeetCode Problem 1144 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives an integer array nums and allows only one type of operation, decreasing any element by 1 . We may perform this operation as many times as needed on any elements. Our goal is to transform the array into a zigzag array with the minimum number of moves. A zigzag array can follow one of two...

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LeetCode 1788 - Maximize the Beauty of the Garden

LeetCode Problem 1788 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Prefix Sum Solution Problem Understanding We are given an integer array flowers , where each element represents the beauty value of a flower in a line. We may remove any flowers we want, while preserving the relative order of the remaining flowers. After removals, the remaining sequence must form a valid garden. A valid garden must satisfy two conditions:...

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Codeforces Beta Round 64

Codeforces Beta Round 64 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1300-2700 | Time: 11m 7s Problem Name Rating Tags Solve Time Verified A Cookies 1300 math 1m 46s ✓ B Text Messaging 1600 expression-parsing, greedy, strings 1m 39s ✓ C Lucky Tickets 2200 binary-search, data-structures, sortings 2m 11s ✓ D Professor's task 2700 data-structures, geometry 2m 2s ✓ E Information Reform 2700 dp, implementation, trees...

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Codeforces Beta Round 16 (Div. 2 Only)

Codeforces Beta Round 16 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-1900 | Time: 7m 6s Problem Name Rating Tags Solve Time Verified A Flag 800 implementation 1m 8s ✓ B Burglar and Matches 900 greedy, implementation, sortings 1m 13s ✓ C Monitor 1800 binary-search, number-theory 1m 37s ✓ D Logging 1900 implementation, strings 1m 34s ✓ E Fish 1900 bitmasks, dp,...

Practice › Codeforces Solutions › Unknown Language Round 3 ›

CF 100J - Interval Coloring

CF 100J - Interval Coloring Rating: 2400 Tags: *special, greedy, math Solve time: 1m 52s Verified: yes Solution Problem Understanding We are asked to color a collection of intervals on the number line such that no three intervals with the same color form a "triple overlap pattern." More concretely, a coloring is invalid if there exist three intervals of the same color where each pair overlaps at some point in...

Practice › Codeforces Solutions › All-Ukrainian School Olympiad in Informatics ›

CF 76B - Mice

CF 76B - Mice Rating: 2100 Tags: greedy, two pointers Solve time: 1m 53s Verified: no Solution Problem Understanding We are given a row of mice located along a horizontal line at coordinate y = Y0 and a row of cheese pieces along another horizontal line at y = Y1 . Each mouse can run directly towards any piece of cheese, and all mice run at the same speed. When...

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LeetCode 455 - Assign Cookies

LeetCode Problem 455 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Greedy, Sorting Solution LeetCode 455, Assign Cookies Problem Understanding This problem asks us to maximize the number of children who can be satisfied with the available cookies. Each child has a greed factor, and each cookie has a size. A child becomes content only if they receive a cookie whose size is greater than or equal to their greed factor....

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LeetCode 954 - Array of Doubled Pairs

LeetCode Problem 954 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding The problem asks whether it is possible to reorder an even-length array arr of integers such that every element can be paired with another element that is exactly double its value. In other words, after reordering, for every index i in the first half of the array, arr[2 * i + 1] should equal 2...

Practice › Codeforces Solutions › Codeforces Beta Round 57 (Div. 2) ›

CF 61D - Eternal Victory

CF 61D - Eternal Victory Rating: 1800 Tags: dfs and similar, graphs, greedy, shortest paths, trees Solve time: 1m 29s Verified: yes Solution Problem Understanding We are asked to find the minimum distance Shapur must travel to visit all cities at least once. The cities are connected in a tree structure, meaning there are exactly $n-1$ bidirectional roads and a unique path between any two cities. Shapur starts at city...

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LeetCode 1217 - Minimum Cost to Move Chips to The Same Position

LeetCode Problem 1217 Difficulty: 🟢 Easy Topics: Array, Math, Greedy Solution Problem Understanding The problem asks us to move n chips located at various positions along a one-dimensional line so that they all end up at the same position. Each chip can be moved either by 2 units at zero cost or by 1 unit at a cost of 1. The input is an array of integers, position , where...

Practice › Codeforces Solutions › School Team Contest 3 (Winter Computer School 2010/11) ›

CF 45I - TCMCF+++

CF 45I - TCMCF+++ Rating: 1400 Tags: greedy Solve time: 2m 18s Verified: no Solution Problem Understanding We are given a list of integers representing problem scores in a contest. A contestant may solve any non-empty subset of these problems, and the final score becomes the product of all chosen values. The task is not to compute the maximum product itself, but to output one subset whose product is as...

Practice › Codeforces Solutions › Codeforces Beta Round 54 (Div. 2) ›

CF 58B - Coins

CF 58B - Coins Rating: 1300 Tags: greedy Solve time: 1m 51s Verified: no Solution Problem Understanding We are given the value of the largest coin denomination, n . We must build a sequence of distinct coin values such that every larger coin is divisible by every smaller coin. Among all valid sequences, we want the one containing the maximum possible number of coins. The output must list the denominations...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120F - Spiders

CF 120F - Spiders Rating: 1400 Tags: dp, greedy, trees Solve time: 1m 11s Verified: yes Solution Problem Understanding We are given a collection of toy spiders. Each spider is a tree, represented by beads (nodes) connected with strings (edges). A spider with $k$ beads has $k-1$ strings connecting its beads so that all beads are connected and there are no cycles. Petya can glue spiders together by identifying some...

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LeetCode 1673 - Find the Most Competitive Subsequence

LeetCode Problem 1673 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Monotonic Stack Solution Here is a complete, detailed technical solution guide for LeetCode 1673 - Find the Most Competitive Subsequence following your formatting rules. Problem Understanding The problem asks us to find the most competitive subsequence of a given integer array nums of size k . A subsequence is formed by deleting zero or more elements from the array without...

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LeetCode 632 - Smallest Range Covering Elements from K Lists

LeetCode Problem 632 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Sliding Window, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us k sorted integer lists, and we must find the smallest inclusive range [a, b] such that the range contains at least one element from every list. Each list is already sorted in non-decreasing order, which is a very important property. Instead of considering arbitrary combinations of...

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LeetCode 1736 - Latest Time by Replacing Hidden Digits

LeetCode Problem 1736 Difficulty: 🟢 Easy Topics: String, Greedy Solution Problem Understanding The problem presents a string time formatted as hh:mm , where h and m are digits representing hours and minutes, respectively. Some digits may be hidden and are represented by a question mark ? . The goal is to replace the ? characters with digits such that the resulting time is the latest valid time possible , considering...

Practice › Codeforces Solutions › Codeforces Beta Round 27 (Codeforces format, Div. 2) ›

CF 27C - Unordered Subsequence

CF 27C - Unordered Subsequence Rating: 1900 Tags: constructive algorithms, greedy Solve time: 1m 18s Verified: no Solution Problem Understanding We are given a sequence of integers, and we are asked to extract the shortest subsequence that is not ordered . A sequence is considered ordered if it is either entirely non-decreasing or entirely non-increasing. In other words, if every consecutive pair either never decreases or never increases, the sequence...

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Codeforces Beta Round 17

Codeforces Beta Round 17 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2900 | Time: 16m 51s Problem Name Rating Tags Solve Time Verified A Noldbach problem 1000 brute-force, math, number-theory 1m 46s ✓ B Hierarchy 1500 dfs-and-similar, dsu, greedy 1m 34s ✓ C Balance 2500 dp 6m 37s ✗ D Notepad 2400 number-theory 3m 4s ✓ E Palisection 2900 strings 3m 50s ✓

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Codeforces Beta Round 63 (Div. 2)

Codeforces Beta Round 63 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2000 | Time: 9m 17s Problem Name Rating Tags Solve Time Verified A Young Physicist 1000 implementation, math 1m 43s ✓ B Bets 1200 greedy, implementation 2m 1s ✓ C Game 2000 implementation 2m 15s ✓ D Dot 1900 dp, games 1m 56s ✓ E Subsegments 1800 data-structures, implementation 1m 22s ✓

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Codeforces Beta Round 74 (Div. 1 Only)

Codeforces Beta Round 74 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1800-2900 | Time: 12m 50s Problem Name Rating Tags Solve Time Verified A Robbery 1800 greedy 1m 54s ✓ B Widget Library 2300 dp, expression-parsing, graphs 2m 3s ✓ C Chip Play 2300 brute-force, data-structures, implementation 2m 14s ✓ D Space mines 2500 geometry 4m 9s ✓ E Fire and Ice...

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LeetCode 1702 - Maximum Binary String After Change

LeetCode Problem 1702 Difficulty: 🟡 Medium Topics: String, Greedy Solution LeetCode 1702, Maximum Binary String After Change Problem Understanding This problem gives us a binary string consisting only of '0' and '1' . We are allowed to repeatedly apply two transformation rules: Replace "00" with "10" Replace "10" with "01" We may perform these operations as many times as we want, in any order, and the goal is to produce...

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Codeforces Beta Round 80 (Div. 1 Only)

Codeforces Beta Round 80 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1100-2900 | Time: 10m 20s Problem Name Rating Tags Solve Time Verified A Testing Pants for Sadness 1100 greedy, implementation, math 1m 39s ✓ B Cthulhu 1500 dfs-and-similar, dsu, graphs 1m 43s ✓ C Russian Roulette 1900 constructive-algorithms, greedy 2m ✓ D Time to Raid Cowavans 2100 brute-force, data-structures, sortings 1m...

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Codeforces Beta Round 55 (Div. 2)

Codeforces Beta Round 55 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 800-2000 | Time: 8m 58s Problem Name Rating Tags Solve Time Verified A Word 800 implementation, strings 1m 11s ✓ B Fortune Telling 1200 implementation, number-theory 1m 57s ✗ C Title 1600 expression-parsing 1m 53s ✓ D Team Arrangement 2000 constructive-algorithms, greedy, implementation 2m 39s ✗ E Shortest Path 2000 graphs, shortest-paths...

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LeetCode 1705 - Maximum Number of Eaten Apples

LeetCode Problem 1705 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem describes a scenario with a series of apple trees that grow apples for n consecutive days. Each day, the tree produces a number of apples given by apples[i] , and these apples have a limited lifespan, given by days[i] . An apple that grows on day i will rot after days[i] days, which...

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LeetCode 1827 - Minimum Operations to Make the Array Increasing

LeetCode Problem 1827 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem asks us to transform a given integer array nums into a strictly increasing array using the minimum number of operations. An operation consists of incrementing any element of the array by 1 . A strictly increasing array is one where each element is strictly less than the next element, i.e., nums[i] < nums[i+1] for all valid...

Practice › Codeforces Solutions › School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules) ›

CF 48D - Permutations

CF 48D - Permutations Rating: 1500 Tags: greedy Solve time: 2m 3s Verified: no Solution Problem Understanding We are given a shuffled array that originally came from concatenating several permutations. Each permutation may have a different size. After concatenation, all numbers were mixed together, so the original grouping disappeared. Our task is to assign every array element to some permutation so that each group forms a valid permutation. A valid...

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CF 79C - Beaver

CF 79C - Beaver Rating: 1800 Tags: data structures, dp, greedy, hashing, strings, two pointers Solve time: 1m 27s Verified: yes Solution Problem Understanding We are asked to find the longest contiguous substring of a string s that avoids certain "boring" substrings. In other words, given a string s and a small list of forbidden patterns b1, b2, ..., bn , we must identify the longest segment of s that...

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LeetCode 976 - Largest Perimeter Triangle

LeetCode Problem 976 Difficulty: 🟢 Easy Topics: Array, Math, Greedy, Sorting Solution Problem Understanding The problem gives us an array of integers called nums , where each integer represents a possible side length. Our goal is to select exactly three lengths that can form a valid triangle with a non-zero area, and among all valid triangles, return the maximum possible perimeter. A triangle is only valid if the sum of...

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CF 123C - Brackets

CF 123C - Brackets Rating: 2300 Tags: combinatorics, dp, greedy Solve time: 2m 19s Verified: yes Solution Problem Understanding We are filling an n × m grid with brackets. Every cell contains either "(" or ")" . The grid is called valid if every monotone path from the top-left corner to the bottom-right corner forms a correct bracket sequence. A monotone path only moves right or down. The second part...

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LeetCode 1414 - Find the Minimum Number of Fibonacci Numbers Whose Sum Is K

LeetCode Problem 1414 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to find the minimum number of Fibonacci numbers whose sum equals a given integer k . Fibonacci numbers are a sequence where each number is the sum of the previous two, starting with 1 and 1. The input k is a positive integer up to 1 billion. The output is a single integer representing...

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LeetCode 670 - Maximum Swap

LeetCode Problem 670 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to take an integer num and find the maximum number we can create by swapping at most two digits . In other words, we can pick two positions in the number, swap their digits, and we want the resulting number to be as large as possible. If no swap would increase the number, we...

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Unknown Language Round 1

Unknown Language Round 1 Type: Special | Problems: 9 | Verified: 9/9 | Rating range: 1300-2400 | Time: 14m 26s Problem Name Rating Tags Solve Time Verified A Factorial 1300 *special, implementation 1m 13s ✓ B Expression 1500 *special, expression-parsing 1m 39s ✓ C Table 1600 *special, greedy, implementation 1m 25s ✓ D Presents 1800 *special, greedy 1m 40s ✓ E Prime Segment 1800 *special, brute-force, math 1m 28s ✓...

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Codeforces Beta Round 87 (Div. 2 Only)

Codeforces Beta Round 87 (Div. 2 Only) Type: Div. 2 | Problems: 2 | Verified: 2/2 | Rating range: 800-1100 | Time: 4m 3s Problem Name Rating Tags Solve Time Verified A Tram 800 implementation 1m 33s ✓ B Little Pigs and Wolves 1100 greedy, implementation 2m 30s ✓

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LeetCode 1589 - Maximum Sum Obtained of Any Permutation

LeetCode Problem 1589 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Prefix Sum Solution LeetCode 1589: Maximum Sum Obtained of Any Permutation Problem Understanding The problem gives us an integer array nums and a collection of range requests. Each request [start, end] asks for the sum of the subarray from index start to end , inclusive. The key twist is that we are allowed to rearrange the elements of nums in...

Practice › Codeforces Solutions › School Team Contest 1 (Winter Computer School 2010/11) ›

CF 39B - Company Income Growth

CF 39B - Company Income Growth Rating: 1300 Tags: greedy Solve time: 3m 27s Verified: yes Solution Problem Understanding We are given a sequence of integers representing the yearly income of a company starting from 2001. The first number is the income in 2001, the second in 2002, and so on. These values may be negative if the company incurred a loss that year. Petya wants to present a "perfect"...

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LeetCode 1403 - Minimum Subsequence in Non-Increasing Order

LeetCode Problem 1403 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives an integer array nums and asks us to build a subsequence whose sum is strictly greater than the sum of all elements that are not included in the subsequence. A subsequence means we are allowed to remove elements from the array while preserving the remaining elements. However, the final answer must be returned in...

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Codeforces Beta Round 79 (Div. 1 Only)

Codeforces Beta Round 79 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2500 | Time: 11m 56s Problem Name Rating Tags Solve Time Verified A Homework 1200 greedy 2m 5s ✓ B Buses 1700 binary-search, data-structures, dp 1m 57s ✓ C Vectors 2000 implementation, math 2m 22s ✓ D Castle 2300 dp, greedy, probabilities 2m 6s ✓ E Candies and Stones 2500 divide-and-conquer,...

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LeetCode 1013 - Partition Array Into Three Parts With Equal Sum

LeetCode Problem 1013 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem gives us an integer array arr and asks whether it can be divided into exactly three non-empty contiguous parts such that all three parts have the same sum. The partitions must preserve the original order of the array. We are not allowed to rearrange elements. Instead, we choose two cut positions that split the array into:...

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LeetCode 1147 - Longest Chunked Palindrome Decomposition

LeetCode Problem 1147 Difficulty: 🔴 Hard Topics: Two Pointers, String, Dynamic Programming, Greedy, Rolling Hash, Hash Function Solution Problem Understanding The problem asks us to decompose a given string text into the largest possible number of contiguous substrings such that the sequence of substrings forms a palindromic pattern. Specifically, the first substring must equal the last substring, the second substring must equal the second-to-last substring, and so on. The goal...

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Codeforces Beta Round 22 (Div. 2 Only)

Codeforces Beta Round 22 (Div. 2 Only) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 800-2300 | Time: 7m 39s Problem Name Rating Tags Solve Time Verified A Second Order Statistics 800 brute-force 1m 21s ✓ B Bargaining Table 1500 brute-force, dp 1m 40s ✓ C System Administrator 1700 graphs 1m 25s ✗ D Segments 1900 greedy, sortings 1m 25s ✓ E Scheme 2300 dfs-and-similar, graphs,...

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CF 134C - Swaps

CF 134C - Swaps Rating: 2200 Tags: constructive algorithms, graphs, greedy Solve time: 2m 15s Verified: no Solution Problem Understanding Each player initially owns cards of exactly one color, their own color. Player i starts with a[i] cards, all of color i . During a swap, two players exchange one card each. A player may only give away cards of their own color, and may never receive a color they...

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LeetCode 1055 - Shortest Way to Form String

LeetCode Problem 1055 Difficulty: 🟡 Medium Topics: Two Pointers, String, Binary Search, Greedy Solution Problem Understanding The problem asks us to construct the string target using the fewest possible subsequences of the string source . A subsequence preserves relative order, but characters do not need to be contiguous. For example, "ace" is a subsequence of "abcde" because we can delete "b" and "d" while keeping the order of the remaining...

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Codeforces Beta Round 23

Codeforces Beta Round 23 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1200-2600 | Time: 11m 15s Problem Name Rating Tags Solve Time Verified A You're Given a String... 1200 brute-force, greedy 1m 55s ✓ B Party 1600 constructive-algorithms, graphs, math 3m 27s ✓ C Oranges and Apples 2500 constructive-algorithms, sortings 2m 29s ✓ D Tetragon 2600 geometry, math 2m 11s ✗ E Tree 2500 dp 1m...

Practice › Codeforces Solutions › Codeforces Beta Round 75 (Div. 2 Only) ›

CF 92B - Binary Number

CF 92B - Binary Number Rating: 1300 Tags: greedy Solve time: 1m 19s Verified: yes Solution Problem Understanding The task is to take a positive integer represented in binary and determine how many steps it takes to reduce it to 1 using a simple iterative process. In each step, if the number is odd, we increment it by 1, and if it is even, we divide it by 2. The...

Practice › Codeforces Solutions › Codeforces Beta Round 67 (Div. 2) ›

CF 75D - Big Maximum Sum

CF 75D - Big Maximum Sum Rating: 2000 Tags: data structures, dp, greedy, implementation, math, trees Solve time: 1m 34s Verified: yes Solution Problem Understanding We are given a set of small arrays and a sequence of indexes indicating how to concatenate them into one larger array. Once the large array is built in this way, the goal is to find the maximum sum of a contiguous subarray. This is...

Practice › Codeforces Solutions › School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules) ›

CF 48F - Snow sellers

CF 48F - Snow sellers Rating: 2800 Tags: greedy, sortings Solve time: 1m 27s Verified: yes Solution Problem Understanding We are asked to plan snow purchases over n days from m companies, ensuring we buy exactly W cubic meters each day. Each company produces a fixed daily amount w[i] , but the cost of all snow from that company decreases linearly: c[i] on day 1, c[i] - a[i] on day...

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CF 83C - Track

CF 83C - Track Rating: 2400 Tags: graphs, greedy, shortest paths Solve time: 2m 22s Verified: yes Solution Problem Understanding We have a rectangular grid. Each cell contains either a terrain type represented by a lowercase letter, the start cell S , or the target cell T . We may move in four directions between side-adjacent cells. Every move costs exactly one minute. The path must start at S and...

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LeetCode 936 - Stamping The Sequence

LeetCode Problem 936 Difficulty: 🔴 Hard Topics: String, Stack, Greedy, Queue Solution Problem Understanding This problem asks us to reconstruct a target string by repeatedly applying a smaller string called stamp . We begin with a string s that has the same length as target , but every character is initially '?' . In one operation, we may place the stamp string onto any valid position in s , and...

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LeetCode 1561 - Maximum Number of Coins You Can Get

LeetCode Problem 1561 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting, Game Theory Solution LeetCode 1561 - Maximum Number of Coins You Can Get Problem Understanding The problem gives us an array called piles , where each element represents the number of coins in a pile. The length of the array is always divisible by 3 , meaning there are exactly 3n piles for some integer n . In every...

Practice › Codeforces Solutions › Codeforces Beta Round 80 (Div. 1 Only) ›

CF 103A - Testing Pants for Sadness

CF 103A - Testing Pants for Sadness Rating: 1100 Tags: greedy, implementation, math Solve time: 1m 39s Verified: yes Solution Problem Understanding The test contains several questions that must be answered in order. Each question has multiple answer choices, and exactly one of them is correct. Vaganych does not know any correct answers in advance, but after making a mistake he remembers which options were wrong. Whenever he clicks a...

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LeetCode 561 - Array Partition

LeetCode Problem 561 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Counting Sort Solution Problem Understanding The problem gives an array nums containing 2n integers. Our task is to divide these integers into exactly n pairs. For each pair (ai, bi) , we take the smaller value, min(ai, bi) . After computing the minimum value from every pair, we sum all of those minimums together. The goal is to arrange the...

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Codeforces Beta Round 3

Codeforces Beta Round 3 Type: Beta | Problems: 4 | Verified: 4/4 | Rating range: 1000-2600 | Time: 14m 42s Problem Name Rating Tags Solve Time Verified A Shortest path of the king 1000 greedy, shortest-paths 4m 37s ✓ B Lorry 1900 greedy, sortings 4m 5s ✓ C Tic-tac-toe 1800 brute-force, games, implementation 4m 37s ✓ D Least Cost Bracket Sequence 2600 greedy 1m 23s ✓

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LeetCode 1330 - Reverse Subarray To Maximize Array Value

LeetCode Problem 1330 Difficulty: 🔴 Hard Topics: Array, Math, Greedy Solution LeetCode 1330 - Reverse Subarray To Maximize Array Value Problem Understanding The problem gives us an integer array nums and defines the "value" of the array as the sum of the absolute differences between every pair of adjacent elements. Formally, the value is: $$\sum_{i=0}^{n-2} |nums[i] - nums[i+1]|$$ We are allowed to reverse exactly one subarray, or equivalently choose any...

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CF 33A - What is for dinner?

CF 33A - What is for dinner? Rating: 1200 Tags: greedy, implementation Solve time: 3m 53s Verified: yes Solution Problem Understanding Each tooth belongs to exactly one row. When Valerie eats one crucian using a row, every tooth in that row loses one unit of viability. A row becomes unusable as soon as at least one tooth inside it would drop below zero. For a single row, the limiting factor...

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LeetCode 1432 - Max Difference You Can Get From Changing an Integer

LeetCode Problem 1432 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem gives us an integer num , and we are allowed to perform a digit replacement operation twice, independently. In one operation, we: Choose a digit x Choose another digit y Replace every occurrence of digit x in the decimal representation of num with y The two operations are completely independent. This means the second operation starts...

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LeetCode 1648 - Sell Diminishing-Valued Colored Balls

LeetCode Problem 1648 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Sorting, Heap (Priority Queue) Solution Here is the complete, detailed technical solution guide for LeetCode 1648 - Sell Diminishing-Valued Colored Balls following your requested structure and formatting rules. Problem Understanding The problem asks us to sell orders number of balls from an inventory of different colored balls in a way that maximizes the total value obtained . Each...

Practice › Codeforces Solutions › Codeforces Beta Round 97 (Div. 1) ›

CF 135A - Replacement

CF 135A - Replacement Rating: 1300 Tags: greedy, implementation, sortings Solve time: 1m 34s Verified: yes Solution Problem Understanding We start with an array of positive integers. We must change exactly one element to a different value, still between 1 and 10^9 . After that single replacement, we sort the array in non-decreasing order. The task is to produce the lexicographically smallest possible sorted array after performing exactly one replacement....

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LeetCode 45 - Jump Game II

LeetCode Problem 45 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem gives an array nums where each value represents the maximum distance you can jump forward from that position. You start at index 0 , and your goal is to reach the final index using the minimum number of jumps possible. For example, if nums[i] = 3 , then from index i you may jump:...

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LeetCode 1183 - Maximum Number of Ones

LeetCode Problem 1183 Difficulty: 🔴 Hard Topics: Math, Greedy, Sorting, Heap (Priority Queue) Solution LeetCode 1183, Maximum Number of Ones Problem Understanding The problem gives us a binary matrix M with dimensions height x width . Every cell in the matrix must contain either 0 or 1 . There is one important restriction: Every square submatrix of size sideLength x sideLength may contain at most maxOnes cells equal to 1...

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LeetCode 1708 - Largest Subarray Length K

LeetCode Problem 1708 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem asks us to find the lexicographically largest contiguous subarray of length k from a given array of distinct integers. Two arrays are compared lexicographically. This means we compare elements from left to right until we find the first position where the arrays differ. The array with the larger value at that position is considered larger. For...

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LeetCode 1578 - Minimum Time to Make Rope Colorful

LeetCode Problem 1578 Difficulty: 🟡 Medium Topics: Array, String, Dynamic Programming, Greedy Solution Problem Understanding The problem requires transforming a rope of balloons into a "colorful" rope, which means no two consecutive balloons share the same color. The input provides a string colors representing the colors of the balloons in order and an array neededTime representing the time in seconds it takes to remove each corresponding balloon. The task is...

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LeetCode 44 - Wildcard Matching

LeetCode Problem 44 Difficulty: 🔴 Hard Topics: String, Dynamic Programming, Greedy, Recursion Solution Problem Understanding This problem asks us to determine whether an entire input string s matches a wildcard pattern p . The pattern supports two special wildcard characters: '?' matches exactly one character. '*' matches any sequence of characters, including an empty sequence. The important detail is that the match must cover the entire string. Partial matches are...

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LeetCode 1792 - Maximum Average Pass Ratio

LeetCode Problem 1792 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us several classes, where each class is represented as [passi, totali] . The value passi tells us how many students currently pass the exam, while totali tells us the total number of students in that class. The pass ratio of a class is: $\frac{pass_i}{total_i}$ We are also given extraStudents , and every...

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LeetCode 179 - Largest Number

LeetCode Problem 179 Difficulty: 🟡 Medium Topics: Array, String, Greedy, Sorting Solution LeetCode 179 - Largest Number Problem Understanding This problem asks us to rearrange a list of non-negative integers so that, when concatenated together, they form the largest possible number. At first glance, this may look like a straightforward sorting problem where we simply sort the numbers in descending order. However, the challenge comes from the fact that the...

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LeetCode 517 - Super Washing Machines

LeetCode Problem 517 Difficulty: 🔴 Hard Topics: Array, Greedy Solution Problem Understanding The problem gives us a line of washing machines, where each machine contains some number of dresses. In one move, we are allowed to choose any subset of machines, and every chosen machine may pass exactly one dress to one of its adjacent machines simultaneously. The goal is to make every washing machine contain the same number of...

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LeetCode 781 - Rabbits in Forest

LeetCode Problem 781 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy Solution Problem Understanding In this problem, every rabbit tells us how many other rabbits share its color. The input array answers contains these responses. If a rabbit says x , that means there are exactly x + 1 rabbits of that color group in total, including itself. The challenge is that we do not know which rabbits belong...

Practice › Codeforces Solutions › School Team Contest 2 (Winter Computer School 2010/11) ›

CF 44J - Triminoes

CF 44J - Triminoes Rating: 2000 Tags: constructive algorithms, greedy Solve time: 4m 23s Verified: no Solution Problem Understanding We are given a rectangular board where some cells are missing. Every remaining cell is already colored either black or white in a chessboard pattern. The task is to cover all existing cells using straight triminoes of size 1 × 3 or 3 × 1 . A trimino always covers three...

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LeetCode 846 - Hand of Straights

LeetCode Problem 846 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding The problem asks us to determine whether a given collection of cards can be rearranged into groups of consecutive numbers, each of size groupSize . Each card is represented by an integer in the array hand , and Alice wants to form groups such that within each group, the card numbers are consecutive and the...

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LeetCode 1764 - Form Array by Concatenating Subarrays of Another Array

LeetCode Problem 1764 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, String Matching Solution Problem Understanding The problem asks us to determine whether we can select disjoint subarrays from a given array nums such that each subarray matches exactly one of the subarrays in the groups array, in order. A subarray is contiguous, and "disjoint" means no element in nums is part of more than one selected subarray. The order...

Practice › Codeforces Solutions › Codeforces Beta Round 11 ›

CF 11E - Forward, march!

CF 11E - Forward, march! Rating: 2800 Tags: binary search, dp, greedy Solve time: 1m 45s Verified: yes Solution Problem Understanding Jack repeats a cyclic sequence consisting of three possible actions. L means a left-foot step, R means a right-foot step, and X means standing still for one beat. The sergeant expects the infinite alternating pattern: L R L R L R ... Jack is allowed to modify his original...

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LeetCode 358 - Rearrange String k Distance Apart

LeetCode Problem 358 Difficulty: 🔴 Hard Topics: Hash Table, String, Greedy, Sorting, Heap (Priority Queue), Counting Solution LeetCode 358 - Rearrange String k Distance Apart Problem Understanding The problem gives us a string s and an integer k . We must rearrange the characters in the string so that identical characters are separated by at least k positions. The phrase "at least distance k " means that if the same...

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LeetCode 452 - Minimum Number of Arrows to Burst Balloons

LeetCode Problem 452 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem is asking us to determine the minimum number of vertical arrows required to burst all balloons represented as intervals along the x-axis. Each balloon is defined by its start and end x-coordinates, [xstart, xend] . An arrow shot at position x bursts any balloon whose interval contains x . The arrows travel infinitely upward, so...

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LeetCode 1505 - Minimum Possible Integer After at Most K Adjacent Swaps On Digits

LeetCode Problem 1505 Difficulty: 🔴 Hard Topics: String, Greedy, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem gives us a numeric string num and an integer k . Each operation allows us to swap two adjacent digits. We may perform at most k such swaps, and the goal is to construct the smallest possible integer, returned as a string. The important detail is that swaps are only allowed...

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LeetCode 1775 - Equal Sum Arrays With Minimum Number of Operations

LeetCode Problem 1775 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , where every element is between 1 and 6 . In one operation, we may choose any element from either array and change it to any value from 1 to 6 . Our goal is to make the total sum of both arrays equal while...

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Codeforces Beta Round 77 (Div. 1 Only)

Codeforces Beta Round 77 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1600-2500 | Time: 7m 52s Problem Name Rating Tags Solve Time Verified A Hockey 1600 implementation, strings 1m 15s ✓ B Lucky Numbers 1800 dp, greedy 1m 52s ✓ C Volleyball 1900 shortest-paths 1m 21s ✓ D Horse Races 2500 dp, math 2m ✓ E Lucky Country 2500 dp, dsu, graphs...

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LeetCode 1558 - Minimum Numbers of Function Calls to Make Target Array

LeetCode Problem 1558 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding This problem asks us to transform an initial array arr of zeros into a target array nums using a minimal number of operations. There are two allowed operations: incrementing any single element of the array by 1, or doubling all elements of the array. The goal is to count the minimum total operations required to reach...

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LeetCode 765 - Couples Holding Hands

LeetCode Problem 765 Difficulty: 🔴 Hard Topics: Greedy, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory Solution LeetCode 765 - Couples Holding Hands Problem Understanding This problem gives us a row of seats represented by the array row , where each value is the ID of the person currently sitting in that seat. The row contains 2n people, meaning there are exactly n couples. The couples are predefined in a very...

Practice › Codeforces Solutions › Codeforces Beta Round 74 (Div. 1 Only) ›

CF 89E - Fire and Ice

CF 89E - Fire and Ice Rating: 2900 Tags: greedy Solve time: 2m 30s Verified: no Solution Problem Understanding Solomon stands on the fortress wall at position 0 . To his right there may exist a chain of ice blocks occupying positions 1, 2, ... . Initially there are no blocks at all. The battlefield is a line of length n . At battlefield position i , there may be...

Practice › Codeforces Solutions › Codeforces Beta Round 54 (Div. 2) ›

CF 58D - Calendar

CF 58D - Calendar Rating: 2000 Tags: greedy, strings Solve time: 1m 23s Verified: yes Solution Problem Understanding We are asked to construct a calendar from a list of city names. Each line of the calendar must contain exactly two city names separated by a given symbol, and all lines must have identical length. The calendar must use each city name exactly once. Among all possible arrangements that satisfy these...

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LeetCode 969 - Pancake Sorting

LeetCode Problem 969 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem is asking us to sort an array of unique integers using only pancake flips . A pancake flip is defined as reversing a prefix of the array from index 0 to index k-1 for some integer k between 1 and the length of the array. The input is a permutation of integers from...

Practice › Codeforces Solutions › Codeforces Beta Round 27 (Codeforces format, Div. 2) ›

CF 27B - Tournament

CF 27B - Tournament Rating: 1300 Tags: bitmasks, brute force, dfs and similar, greedy Solve time: 1m 3s Verified: yes Solution Problem Understanding We are asked to reconstruct the missing result of a round-robin tournament. There are n participants, and every participant plays against every other participant exactly once. Each match has a clear winner and a loser, and no two participants have the same intrinsic ability: a lower "sleep...

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LeetCode 1196 - How Many Apples Can You Put into the Basket

LeetCode Problem 1196 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding This problem is asking us to determine how many apples we can fit into a basket with a maximum carrying capacity of 5000 units of weight. We are given an array weight where each element represents the weight of a single apple. The goal is to maximize the number of apples placed into the basket without exceeding...

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LeetCode 1710 - Maximum Units on a Truck

LeetCode Problem 1710 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution LeetCode 1710 - Maximum Units on a Truck Problem Understanding The problem gives us several types of boxes, where each box type contains two values: The number of boxes available for that type The number of units inside each box of that type We also have a truck that can carry at most truckSize boxes total, regardless of type....

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LeetCode 1167 - Minimum Cost to Connect Sticks

LeetCode Problem 1167 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array of positive integers called sticks , where each value represents the length of a stick. We are allowed to repeatedly connect any two sticks together. If we connect sticks with lengths x and y , the operation costs x + y , and the resulting stick has length x...

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CF 22D - Segments

CF 22D - Segments Rating: 1900 Tags: greedy, sortings Solve time: 1m 25s Verified: yes Solution Problem Understanding We are given several closed intervals on the number line. A nail placed at an integer coordinate covers every segment that contains that coordinate, including endpoints. The task is to choose as few nail positions as possible so that every segment contains at least one chosen point. Another way to think about...

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LeetCode 625 - Minimum Factorization

LeetCode Problem 625 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to find the smallest positive integer x such that the product of all of its digits equals the given integer num . In other words, we want to decompose num into a multiplication of decimal digits from 1 to 9 , then arrange those digits to form the numerically smallest possible integer. For example:...

Practice › Codeforces Solutions › Codeforces Beta Round 30 (Codeforces format) ›

CF 30E - Tricky and Clever Password

CF 30E - Tricky and Clever Password Rating: 2800 Tags: binary search, constructive algorithms, data structures, greedy, hashing, strings Solve time: 1m 50s Verified: yes Solution Problem Understanding We are given a single lowercase string. Somewhere inside this string, there exists a hidden palindrome of odd length, but the palindrome was split into three consecutive parts: a prefix, a middle part, a suffix. The prefix and suffix have the same...

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LeetCode 1402 - Reducing Dishes

LeetCode Problem 1402 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Sorting Solution Problem Understanding In this problem, we are given an integer array called satisfaction , where each element represents the satisfaction level of a dish prepared by a chef. The chef can cook dishes in any order, and each dish takes exactly one unit of time to prepare. The important detail is how the score is calculated. If...

Practice › Codeforces Solutions › Codeforces Beta Round 30 (Codeforces format) ›

CF 30D - King's Problem?

CF 30D - King's Problem? Rating: 2600 Tags: geometry, greedy Solve time: 2m 12s Verified: no Solution Problem Understanding We have n + 1 cities. The first n cities lie on the x-axis at positions (x1, 0), (x2, 0), ..., (xn, 0) . One additional city is somewhere off the axis at (x_{n+1}, y_{n+1}) . The king starts from city k . He must visit every city at least once,...

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LeetCode 1024 - Video Stitching

LeetCode Problem 1024 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem asks us to cover a sporting event that lasts time seconds using a set of video clips. Each clip is defined by its start and end times, [starti, endi] , and clips can overlap or extend beyond each other. We can cut clips into smaller segments freely, meaning that if a clip covers [0,7]...

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LeetCode 1338 - Reduce Array Size to The Half

LeetCode Problem 1338 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue) Solution Here is a complete, detailed technical solution guide for LeetCode 1338, following your requested formatting and structure. Problem Understanding The problem asks us to reduce the size of an integer array arr by removing all occurrences of a selected set of integers. Specifically, we want to find the minimum size of such a set...

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Yandex.Algorithm 2011: Round 2

Yandex.Algorithm 2011: Round 2 Type: Special | Problems: 5 | Verified: 5/5 | Rating range: 1600-2700 | Time: 11m 50s Problem Name Rating Tags Solve Time Verified A Reflection 1600 math 2m 9s ✓ B Tetris revisited 2200 constructive-algorithms, graph-matchings, greedy 2m 5s ✓ C Genetic engineering 2500 dp, string-suffix-structures, trees 2m 12s ✓ D Powerful array 2200 data-structures, implementation, math 3m 46s ✓ E Long sequence 2700 brute-force, math,...

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Codeforces Beta Round 5

Codeforces Beta Round 5 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1000-2400 | Time: 5m 59s Problem Name Rating Tags Solve Time Verified A Chat Servers Outgoing Traffic 1000 implementation 1m 9s ✓ B Center Alignment 1200 implementation, strings 1m 24s ✓ C Longest Regular Bracket Sequence 1900 constructive-algorithms, data-structures, dp 1m 21s ✓ D Follow Traffic Rules 2100 implementation, math 54s ✓ E Bindian Signalizing...

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CF 23A - You're Given a String...

CF 23A - You're Given a String... Rating: 1200 Tags: brute force, greedy Solve time: 1m 55s Verified: yes Solution Problem Understanding We are given a string of lowercase letters, and the task is to find the length of the longest substring that occurs at least twice in the string. The repeated occurrences may overlap. The input is a single string of at most 100 characters. The output is a...

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Codeforces Beta Round 54 (Div. 2)

Codeforces Beta Round 54 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 3/5 | Rating range: 1000-2400 | Time: 7m 51s Problem Name Rating Tags Solve Time Verified A Chat room 1000 greedy, strings 1m 20s ✓ B Coins 1300 greedy 1m 51s ✗ C Trees 1800 brute-force 1m 13s ✓ D Calendar 2000 greedy, strings 1m 23s ✓ E Expression 2400 dp 2m 4s ✗

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Codeforces Beta Round 89 (Div. 2)

Codeforces Beta Round 89 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1000-2000 | Time: 10m 4s Problem Name Rating Tags Solve Time Verified A String Task 1000 implementation, strings 1m 38s ✓ B Present from Lena 1000 constructive-algorithms, implementation 1m 42s ✓ C Fancy Number 1900 brute-force, greedy, sortings 2m 51s ✓ D Caesar's Legions 1700 dp 1m 37s ✓ E Bertown roads...

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LeetCode 1386 - Cinema Seat Allocation

LeetCode Problem 1386 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Bit Manipulation Solution Here is a complete, detailed technical solution guide for LeetCode 1386 - Cinema Seat Allocation in a single, comprehensive response following your formatting rules. Problem Understanding The problem describes a cinema with n rows, each containing exactly ten seats, labelled 1 through 10. Some of these seats are already reserved, given in the input array reservedSeats...

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CF 91A - Newspaper Headline

CF 91A - Newspaper Headline Rating: 1500 Tags: greedy, strings Solve time: 1m 57s Verified: yes Solution Problem Understanding We have a source string s1 , which represents the headline of one newspaper. We may take as many copies of this headline as we want and concatenate them together. From the resulting long string, we are allowed to delete arbitrary characters while keeping the remaining characters in order. The target...

Practice › Codeforces Solutions › Codeforces Beta Round 26 (Codeforces format) ›

CF 26C - Parquet

CF 26C - Parquet Rating: 2000 Tags: combinatorics, constructive algorithms, greedy, implementation Solve time: 2m 9s Verified: no Solution Problem Understanding We are asked to tile a rectangular floor of size n × m using three types of parquet planks. The first type is a 1×2 horizontal plank, the second is a 2×1 vertical plank, and the third is a 2×2 square plank. The goal is to cover the entire...

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LeetCode 581 - Shortest Unsorted Continuous Subarray

LeetCode Problem 581 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding The problem gives an integer array nums and asks for the length of the shortest continuous subarray such that, if only that subarray is sorted in non-decreasing order, the entire array becomes sorted. In other words, the array is "almost sorted", except for some misplaced elements. We need to identify the smallest...

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Codeforces Beta Round 96 (Div. 1)

Codeforces Beta Round 96 (Div. 1) Type: Div. 1 | Problems: 5 | Verified: 3/5 | Rating range: 1300-2700 | Time: 9m 16s Problem Name Rating Tags Solve Time Verified A Turing Tape 1300 implementation 1m 39s ✓ B Piet 2100 implementation 1m 56s ✓ C Logo Turtle 1800 dp 1m 52s ✓ D Constants in the language of Shakespeare 2100 constructive-algorithms, dp, greedy 2m 2s ✗ E Bits of...

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LeetCode 860 - Lemonade Change

LeetCode Problem 860 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding This problem simulates a lemonade stand where each lemonade costs $5 . Customers come in a specific order and pay with a $5 , $10 , or $20 bill. The challenge is to provide exact change to every customer as they pay. The input is a list of integers bills , where each element represents the bill a...

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Yandex.Algorithm Open 2011: Qualification 1

Yandex.Algorithm Open 2011: Qualification 1 Type: Special | Problems: 5 | Verified: 3/5 | Rating range: 1400-2700 | Time: 13m 8s Problem Name Rating Tags Solve Time Verified A Plug-in 1400 implementation 1m 36s ✓ B Sequence Formatting 1700 implementation, strings 1m 43s ✓ C Average Score 1700 greedy, math, sortings 3m 31s ✓ D Polycarp's Picture Gallery 2100 constructive-algorithms, greedy 2m 48s ✗ E Pairs 2700 dfs-and-similar, dp, dsu...

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CF 79A - Bus Game

CF 79A - Bus Game Rating: 1200 Tags: greedy Solve time: 1m 20s Verified: yes Solution Problem Understanding We are asked to simulate a turn-based game involving two players, Ciel and Hanako, who alternate taking coins from a common pile. The pile initially contains x 100-yen coins and y 10-yen coins. On each turn, the active player must remove exactly 220 yen. Ciel prefers to maximize the number of 100-yen...

Practice › Codeforces Solutions › Codeforces Beta Round 89 (Div. 2) ›

CF 118C - Fancy Number

CF 118C - Fancy Number Rating: 1900 Tags: brute force, greedy, sortings, strings Solve time: 2m 51s Verified: yes Solution Problem Understanding We are given a string of digits representing a car number. The number is considered beautiful if at least k positions contain the same digit. We may change any digit into another digit, and changing digit a into digit b costs |a - b| . The task has...

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Codeforces Beta Round 34 (Div. 2)

Codeforces Beta Round 34 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2000 | Time: 7m 19s Problem Name Rating Tags Solve Time Verified A Reconnaissance 2 800 implementation 1m 18s ✓ B Sale 900 greedy, sortings 1m 19s ✓ C Page Numbers 1300 expression-parsing, implementation, sortings 1m 7s ✓ D Road Map 1600 dfs-and-similar, graphs 1m 29s ✓ E Collisions 2000 brute-force, implementation,...

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CF 50A - Domino piling

CF 50A - Domino piling Rating: 800 Tags: greedy, math Solve time: 1m 5s Verified: yes Solution Problem Understanding We are asked to place as many standard dominoes as possible on a rectangular board of size M by N . Each domino covers exactly two adjacent squares, and dominoes cannot overlap or extend outside the board. The input gives us two integers, M and N , representing the height and...

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LeetCode 1567 - Maximum Length of Subarray With Positive Product

LeetCode Problem 1567 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem asks us to find the length of the longest contiguous subarray whose product of elements is strictly positive. We are given an integer array nums , which may contain positive numbers, negative numbers, and zeros. A subarray must consist of consecutive elements from the original array. Among all possible subarrays, we need to determine...

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LeetCode 555 - Split Concatenated Strings

LeetCode Problem 555 Difficulty: 🟡 Medium Topics: Array, String, Greedy Solution Problem Understanding The problem gives an array of strings, and we must arrange them into a circular concatenation while preserving the original order of the strings. For every individual string, we are allowed to either keep it as-is or reverse it before joining it into the loop. After constructing this circular string, we may cut the loop at any...

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LeetCode 2029 - Stone Game IX

LeetCode Problem 2029 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Counting, Game Theory Solution Problem Understanding The problem describes a turn-based game between Alice and Bob with a row of stones, each having a numeric value. On each turn, a player removes any stone of their choice. The game has a losing condition based on the sum of removed stones: if the cumulative sum of all removed stones becomes divisible...

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LeetCode 1785 - Minimum Elements to Add to Form a Given Sum

LeetCode Problem 1785 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us an integer array nums , a maximum allowed absolute value limit , and a target sum called goal . Every element in the array already satisfies the condition: abs(nums[i]) <= limit We are allowed to add new integers to the array, but every newly added integer must also satisfy the same restriction: abs(x) <=...

Practice › Codeforces Solutions › Codeforces Beta Round 37 ›

CF 37B - Computer Game

CF 37B - Computer Game Rating: 1800 Tags: greedy, implementation Solve time: 1m 56s Verified: yes Solution Problem Understanding The boss starts with max health and regenerates reg health every second. We own several scrolls. Each scroll can only be activated when the boss health is at most some percentage of the original health. Once activated, that scroll permanently adds its damage per second to our total damage output. The...

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LeetCode 881 - Boats to Save People

LeetCode Problem 881 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution LeetCode 881, Boats to Save People Problem Understanding This problem asks us to determine the minimum number of boats required to rescue all people, given two constraints. Each boat can carry at most two people, and the combined weight of the people in a boat cannot exceed the given weight limit. The input consists of: people ,...

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Codeforces Beta Round 31 (Div. 2, Codeforces format)

Codeforces Beta Round 31 (Div. 2, Codeforces format) Type: Div. 2 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2400 | Time: 6m 52s Problem Name Rating Tags Solve Time Verified A Worms Evolution 1200 implementation 1m 46s ✓ B Sysadmin Bob 1500 greedy, implementation, strings 1m 11s ✓ C Schedule 1700 implementation 58s ✓ D Chocolate 2000 dfs-and-similar, implementation 59s ✓ E TV Game 2400 dp 1m 58s...

Practice › Codeforces Solutions › School Regional Team Contest, Saratov, 2011 ›

CF 120I - Luck is in Numbers

CF 120I - Luck is in Numbers Rating: 2200 Tags: greedy Solve time: 1m 27s Verified: yes Solution Problem Understanding The problem asks us to find the next "lucky" ticket number that is strictly greater than a given ticket. Each ticket is a string of digits with even length, denoted 2_n_. A ticket's "happiness" is defined by representing each digit as a seven-segment display, pairing the left half of the...

Practice › Codeforces Solutions › Yandex.Algorithm Open 2011: Qualification 1 ›

CF 81D - Polycarp's Picture Gallery

CF 81D - Polycarp's Picture Gallery Rating: 2100 Tags: constructive algorithms, greedy Solve time: 2m 48s Verified: no Solution Problem Understanding We have several photo albums. Album i contains a[i] photos. We must build a cyclic gallery containing exactly n photos. Instead of choosing concrete photo IDs, we only need to output the album number for each position. The gallery is circular, so every position has two neighbors. Position 1...

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LeetCode 945 - Minimum Increment to Make Array Unique

LeetCode Problem 945 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Counting Solution Problem Understanding This problem asks us to take an integer array nums and perform a series of increment operations so that every element in the array becomes unique. An increment operation increases an element by exactly 1. The goal is to compute the minimum number of such moves required. In simpler terms, we are asked: given an array...

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LeetCode 1739 - Building Boxes

LeetCode Problem 1739 Difficulty: 🔴 Hard Topics: Math, Binary Search, Greedy Solution Problem Understanding The problem gives us n identical unit cubes that must be placed inside a cubic room. The goal is to minimize how many boxes directly touch the floor. The placement rule is the important part of the problem. A box can only support another box on top of it if all four of its vertical sides...

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LeetCode 1663 - Smallest String With A Given Numeric Value

LeetCode Problem 1663 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding The problem asks us to construct a lowercase string of length n such that the sum of the numeric values of its characters equals k , while also ensuring the resulting string is lexicographically smallest . Each lowercase letter has a numeric value equal to its position in the alphabet: a = 1 b = 2 c =...

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LeetCode 678 - Valid Parenthesis String

LeetCode Problem 678 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Stack, Greedy Solution Problem Understanding This problem is asking whether a string containing the characters '(' , ')' , and '*' can be considered a valid parenthesis string. In essence, '(' must be matched by a ')' in the correct order, and '*' can act as a flexible placeholder that behaves as '(' , ')' , or an empty string....

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CF 125C - Hobbits' Party

CF 125C - Hobbits' Party Rating: 1600 Tags: constructive algorithms, greedy Solve time: 2m 5s Verified: no Solution Problem Understanding We need to construct as many party days as possible using exactly n hobbits. Every day has a guest list. The construction must satisfy two conditions. First, every pair of different days must share at least one hobbit. If day A and day B exist, there must be some hobbit...

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LeetCode 680 - Valid Palindrome II

LeetCode Problem 680 Difficulty: 🟢 Easy Topics: Two Pointers, String, Greedy Solution Problem Understanding The problem asks whether a given string s can become a palindrome after deleting at most one character . A palindrome is a string that reads the same forwards and backwards. For example, "aba" and "racecar" are palindromes because their characters match symmetrically from both ends. The input consists of a single string s made only...

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LeetCode 1798 - Maximum Number of Consecutive Values You Can Make

LeetCode Problem 1798 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution LeetCode 1798 - Maximum Number of Consecutive Values You Can Make Problem Understanding The problem gives us an array of coin values, where each coin can be used at most once. We are asked to determine the maximum number of consecutive integer values that can be formed starting from 0 . More specifically, if the answer is k ,...

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LeetCode 1296 - Divide Array in Sets of K Consecutive Numbers

LeetCode Problem 1296 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding The problem gives us an integer array nums and an integer k . We need to determine whether it is possible to divide all numbers in the array into groups where: Each group contains exactly k numbers The numbers inside each group are consecutive integers Every element in the array must belong to exactly one...

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LeetCode 1754 - Largest Merge Of Two Strings

LeetCode Problem 1754 Difficulty: 🟡 Medium Topics: Two Pointers, String, Greedy Solution Problem Understanding This problem asks us to build the lexicographically largest possible string by repeatedly choosing characters from the front of two given strings. At every step, we may take the first character from either word1 or word2 , append it to the result, and remove it from its original string. The important detail is that we are...

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Codeforces Beta Round 58

Codeforces Beta Round 58 Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1300-2700 | Time: 8m 15s Problem Name Rating Tags Solve Time Verified A A Student's Dream 1300 greedy, math 1m 13s ✓ B Tyndex.Brome 1800 binary-search, implementation 1m 18s ✓ C Inquisition 2300 geometry, implementation, sortings 1m 32s ✓ D Wormhouse 2300 dfs-and-similar, graphs 2m 15s ✗ E World Evil 2700 dp, flows 1m 57s...

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LeetCode 1053 - Previous Permutation With One Swap

LeetCode Problem 1053 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks us to find the lexicographically largest permutation that is still smaller than the given array, using exactly one swap operation. A permutation is considered lexicographically smaller if, at the first position where two arrays differ, the new array has a smaller value. For example: [3,1,2] is smaller than [3,2,1] because at index 1 , 1...

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Codeforces Beta Round 26 (Codeforces format)

Codeforces Beta Round 26 (Codeforces format) Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 900-2400 | Time: 7m 38s Problem Name Rating Tags Solve Time Verified A Almost Prime 900 number-theory 1m 18s ✓ B Regular Bracket Sequence 1400 greedy 1m 20s ✓ C Parquet 2000 combinatorics, constructive-algorithms, greedy 2m 9s ✗ D Tickets 2400 combinatorics, math, probabilities 1m 14s ✓ E Multithreading 2400 constructive-algorithms 1m 37s...

Practice › Codeforces Solutions › Codeforces Beta Round 26 (Codeforces format) ›

CF 26B - Regular Bracket Sequence

CF 26B - Regular Bracket Sequence Rating: 1400 Tags: greedy Solve time: 1m 20s Verified: yes Solution Problem Understanding We are given a string consisting solely of opening and closing parentheses. The task is to determine the maximum length of a subsequence that forms a valid, or regular, bracket sequence. A regular bracket sequence is one in which every opening bracket has a corresponding closing bracket in the correct order....

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LeetCode 942 - DI String Match

LeetCode Problem 942 Difficulty: 🟢 Easy Topics: Array, Two Pointers, String, Greedy Solution Problem Understanding In this problem, we are given a string s consisting only of the characters 'I' and 'D' . The string has length n , and we must construct a permutation of the integers from 0 to n , inclusive. A permutation means every number in the range appears exactly once. Since the range is [0,...

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CF 67B - Restoration of the Permutation

CF 67B - Restoration of the Permutation Rating: 1800 Tags: greedy Solve time: 1m 59s Verified: yes Solution Problem Understanding We are given a permutation A of numbers from 1 to n . For every value i , we know a number b[i] . This number describes how many elements appear before i in the permutation and are at least i + k . The condition is attached to the...

Practice › Codeforces Solutions › Codeforces Beta Round 34 (Div. 2) ›

CF 34B - Sale

CF 34B - Sale Rating: 900 Tags: greedy, sortings Solve time: 1m 19s Verified: yes Solution Problem Understanding Bob is at a sale with a collection of old TVs, each with a price. Some TVs are free, some have positive prices, and some even have negative prices, which means the owner is willing to pay Bob to take them away. Bob can carry at most m TVs, and he wants...

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Codeforces Beta Round 57 (Div. 2)

Codeforces Beta Round 57 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 800-2000 | Time: 14m 51s Problem Name Rating Tags Solve Time Verified A Ultra-Fast Mathematician 800 implementation 2m 4s ✓ B Hard Work 1300 strings 6m 35s ✓ C Capture Valerian 2000 math 2m 49s ✓ D Eternal Victory 1800 dfs-and-similar, graphs, greedy 1m 29s ✓ E Enemy is weak 1900 data-structures,...

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LeetCode 527 - Word Abbreviation

LeetCode Problem 527 Difficulty: 🔴 Hard Topics: Array, String, Greedy, Trie, Sorting Solution Problem Understanding The problem asks us to compute minimal unique abbreviations for an array of distinct strings. An abbreviation replaces the middle characters of a word with a count, keeping the first and last characters. For example, "internal" becomes "i6l" because there are six letters between i and l . The challenge arises when multiple words share...

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School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules)

School Personal Contest #3 (Winter Computer School 2010/11) - Codeforces Beta Round 45 (ACM-ICPC Rules) Type: Beta | Problems: 8 | Verified: 6/8 | Rating range: 900-2800 | Time: 15m 12s Problem Name Rating Tags Solve Time Verified A Rock-paper-scissors 900 implementation, schedules 1m 31s ✓ B Land Lot 1200 brute-force, implementation 1m 47s ✓ C The Race 1800 math 1m 54s ✓ D Permutations 1500 greedy 2m 3s ✗...

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Codeforces Beta Round 75 (Div. 1 Only)

Codeforces Beta Round 75 (Div. 1 Only) Type: Div. 1 | Problems: 5 | Verified: 5/5 | Rating range: 1500-2600 | Time: 12m 45s Problem Name Rating Tags Solve Time Verified A Newspaper Headline 1500 greedy, strings 1m 57s ✓ B Queue 1500 binary-search, data-structures 2m 10s ✓ C Ski Base 2300 combinatorics, dsu, graphs 3m 29s ✓ D Grocer's Problem 2600 constructive-algorithms, graphs, greedy 2m 25s ✓ E Igloo...

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LeetCode 738 - Monotone Increasing Digits

LeetCode Problem 738 Difficulty: 🟡 Medium Topics: Math, Greedy Solution Problem Understanding The problem asks us to find the largest integer less than or equal to a given number n , such that its digits are monotone increasing. A number has monotone increasing digits when every digit is less than or equal to the digit that comes after it. For example: 1234 is monotone increasing because 1 <= 2 <=...

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LeetCode 1509 - Minimum Difference Between Largest and Smallest Value in Three Moves

LeetCode Problem 1509 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us an integer array nums , and we are allowed to perform at most three moves. In each move, we may select any element and change it to any value we want. After making up to three modifications, we must minimize the difference between the largest and smallest values remaining in the array. In...

Practice › Codeforces Solutions › All-Ukrainian School Olympiad in Informatics ›

CF 76D - Plus and xor

CF 76D - Plus and xor Rating: 1700 Tags: dp, greedy, math Solve time: 1m 46s Verified: yes Solution Problem Understanding We are given two non-negative integers, A and B . We need to construct two other non-negative integers, X and Y , such that: their sum equals A their bitwise xor equals B Among all valid pairs, we must output the one with the smallest possible X . The...

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LeetCode 1363 - Largest Multiple of Three

LeetCode Problem 1363 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Greedy, Sorting Solution I can do that, but the guide will be very long and may get truncated in a single message because of the required depth and sections. To preserve quality and include everything comprehensively, I recommend splitting it into 2 parts : Part 1 Problem Understanding Approaches Algorithm Walkthrough Python Solution Go Solution Part 2 Worked Examples...

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Codeforces Beta Round 53

Codeforces Beta Round 53 Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 1300-3000 | Time: 8m 25s Problem Name Rating Tags Solve Time Verified A Square Earth? 1300 dfs-and-similar, greedy, implementation 1m 22s ✓ B Martian Architecture 1600 implementation 1m 37s ✓ C Array 1900 combinatorics, math 1m 21s ✓ D Journey 2500 dp, math 2m 2s ✓ E Chess 3000 math, shortest-paths 2m 3s ✓

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LeetCode 1481 - Least Number of Unique Integers after K Removals

LeetCode Problem 1481 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Counting Solution Problem Understanding This problem asks us to minimize the number of unique integers in an array after removing exactly k elements. In other words, we are given a list arr and a number k , and we need to strategically remove k elements so that the count of distinct integers left in the array is as...

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LeetCode 984 - String Without AAA or BBB

LeetCode Problem 984 Difficulty: 🟡 Medium Topics: String, Greedy Solution Problem Understanding The problem gives us two integers, a and b , representing how many 'a' characters and 'b' characters we must place into a string. Our task is to construct any valid string of length a + b such that: Exactly a characters are 'a' Exactly b characters are 'b' The substring "aaa" never appears The substring "bbb" never...

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Codeforces Beta Round 35 (Div. 2)

Codeforces Beta Round 35 (Div. 2) Type: Div. 2 | Problems: 5 | Verified: 5/5 | Rating range: 1000-2100 | Time: 7m 52s Problem Name Rating Tags Solve Time Verified A Shell Game 1000 implementation 1m 26s ✓ B Warehouse 1700 implementation 1m 21s ✓ C Fire Again 1500 brute-force, dfs-and-similar, shortest-paths 2m 10s ✓ D Animals 1700 dp, greedy 1m 14s ✓ E Parade 2100 data-structures, sortings 1m 41s...

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LeetCode 955 - Delete Columns to Make Sorted II

LeetCode Problem 955 Difficulty: 🟡 Medium Topics: Array, String, Greedy Solution Problem Understanding This problem asks us to remove the minimum number of columns from a list of equal length strings so that the resulting array of strings becomes lexicographically sorted. The important detail is that when we delete a column, we delete that character position from every string simultaneously. We cannot selectively delete characters from individual strings. Lexicographic order...

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LeetCode 1326 - Minimum Number of Taps to Open to Water a Garden

LeetCode Problem 1326 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding The problem describes a one-dimensional garden that stretches from position 0 to position n . At every integer position i , there is a tap that may water some interval around it. Specifically, if tap i is opened, it covers the interval: $$[i - ranges[i],\ i + ranges[i]]$$ The goal is to determine the minimum number...

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LeetCode 484 - Find Permutation

LeetCode Problem 484 Difficulty: 🟡 Medium Topics: Array, String, Stack, Greedy Solution Problem Understanding The problem gives us a string s consisting only of the characters 'I' and 'D' . This string describes the relationship between adjacent numbers in a hidden permutation. If s[i] == 'I' , then the permutation must satisfy: perm[i] < perm[i + 1] If s[i] == 'D' , then the permutation must satisfy: perm[i] > perm[i...

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LeetCode 1537 - Get the Maximum Score

LeetCode Problem 1537 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Dynamic Programming, Greedy Solution Here’s a complete, detailed technical solution guide for LeetCode 1537 - Get the Maximum Score following your requested format. Problem Understanding The problem gives us two strictly increasing arrays of integers, nums1 and nums2 , and asks us to compute the maximum sum obtainable along a valid path . A valid path starts from either array...

Practice › Codeforces Solutions › School Team Contest 3 (Winter Computer School 2010/11) ›

CF 45E - Director

CF 45E - Director Rating: 2000 Tags: constructive algorithms, greedy Solve time: 1m 49s Verified: yes Solution Problem Understanding We have two independent lists, one containing names and one containing surnames. Every name must be paired with exactly one surname, and every surname must be used exactly once. After choosing the matching, we print all pairs in one comma-separated line. The optimization target has two layers. First, we want as...

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CF 17B - Hierarchy

CF 17B - Hierarchy Rating: 1500 Tags: dfs and similar, dsu, greedy, shortest paths Solve time: 1m 34s Verified: yes Solution Problem Understanding We have employees and directed supervisor offers between them. An offer (a, b, c) means employee a is willing to supervise employee b for cost c . Qualifications are strictly decreasing along every offer, so q[a] > q[b] . The final hierarchy must be a rooted tree....

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CF 89A - Robbery

CF 89A - Robbery Rating: 1800 Tags: greedy Solve time: 1m 54s Verified: yes Solution Problem Understanding The bank stores diamonds in a row of cells. After every minute, the security system checks the sums of every adjacent pair: $$a_1 + a_2,\ a_2 + a_3,\ \dots,\ a_{n-1} + a_n$$ If any of these sums changes compared to the previous check, the alarm triggers. Joe may move diamonds between checks. One...

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Codeforces Beta Round 12 (Div 2 Only)

Codeforces Beta Round 12 (Div 2 Only) Type: Beta | Problems: 5 | Verified: 5/5 | Rating range: 800-2400 | Time: 6m 41s Problem Name Rating Tags Solve Time Verified A Super Agent 800 implementation 1m 15s ✓ B Correct Solution? 1100 implementation, sortings 1m 19s ✓ C Fruits 1100 greedy, implementation, sortings 1m 2s ✓ D Ball 2400 data-structures, sortings 1m 52s ✓ E Start of the session 2100...

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LeetCode 1671 - Minimum Number of Removals to Make Mountain Array

LeetCode Problem 1671 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Greedy Solution Problem Understanding This problem asks us to remove the minimum number of elements from an array so that the remaining elements form a valid mountain array. A mountain array has two strict phases: A strictly increasing sequence Followed by a strictly decreasing sequence There must be a valid peak somewhere in the middle, meaning the peak...

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LeetCode 2007 - Find Original Array From Doubled Array

LeetCode Problem 2007 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding The problem gives us an array called changed , which was supposedly created from another array called original . The transformation process works like this: Take every number in original . Append its doubled value, meaning 2 * x . Shuffle all the numbers together. For example, if: original = [1, 3, 4] then the...

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LeetCode 11 - Container With Most Water

LeetCode Problem 11 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy Solution Problem Understanding The problem gives an array called height , where each element represents the height of a vertical line drawn on a coordinate plane. The line at index i starts at (i, 0) and ends at (i, height[i]) . We want to choose two different lines that, together with the x-axis, form a container capable of holding...

Practice › Codeforces Solutions › Codeforces Round 933 (Div. 3) ›

CF 1941B - Rudolf and 121

CF 1941B - Rudolf and 121 Rating: 1000 Tags: brute force, dp, greedy, math Solve time: 2m 47s Verified: yes Solution Problem Understanding We are given an array of non-negative integers. In one operation, we choose an index $i$ such that $2 \le i \le n-1$, and decrease three consecutive elements in the following way: $$a_{i-1} \mathrel{-}= 1,\quad a_i \mathrel{-}= 2,\quad a_{i+1} \mathrel{-}= 1$$ The operation may be used any...

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CF 4B - Before an Exam

CF 4B - Before an Exam Rating: 1200 Tags: constructive algorithms, greedy Solve time: 1m 12s Verified: yes Solution Problem Understanding We are given d days and a target total number of study hours, sumTime . For every day, Peter must study at least minTime[i] hours and at most maxTime[i] hours. The task is to construct any valid schedule whose total sum is exactly sumTime . This is not an...

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CF 1941C - Rudolf and the Ugly String

CF 1941C - Rudolf and the Ugly String Rating: 900 Tags: dp, greedy, strings Solve time: 2m 41s Verified: yes Solution Problem Understanding We are given a string and want to remove the minimum number of characters so that the resulting string no longer contains "pie" or "map" as a substring. The key detail is that deletions can happen at arbitrary positions. We are not rearranging characters, only deleting some...

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Codeforces Round 933 (Div. 3)

Codeforces Round 933 (Div. 3) Type: Div. 3 | Problems: 7 | Verified: 6/7 | Rating range: 800-2000 | Time: 12m 58s Problem Name Rating Tags Solve Time Verified A Rudolf and the Ticket 800 brute-force, math 1m 23s ✓ B Rudolf and 121 1000 brute-force, dp, greedy 2m 47s ✓ C Rudolf and the Ugly String 900 dp, greedy, strings 2m 41s ✓ D Rudolf and the Ball Game...

Practice › LeetCode › LeetCode (archived) › LeetCode 10xx ›

LeetCode 1053: Previous Permutation With One Swap

Problem Restatement We are given an array of positive integers arr . We need to return the lexicographically largest permutation smaller than arr that can be obtained with at most one swap. If not possible, return arr . The official constraints state that 1 <= arr.length <= 10^4 and 1 <= arr[i] <= 10^4 . Input and Output Item Meaning Input Array arr Output Previous permutation with at most one...

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LeetCode 1029: Two City Scheduling

Problem Restatement We have 2n people who must each travel to one of two cities: city A or city B. Exactly n people must go to city A and exactly n must go to city B. The cost to send person i to city A is costs[i][0] and to city B is costs[i][1] . We need to return the minimum total cost. The official constraints state that 2 <= costs.length...

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LeetCode 1024: Video Stitching

Problem Restatement We are given an array clips where clips[i] = [start_i, end_i] represents a video clip covering the time interval [start_i, end_i] . We want to cover the interval [0, time] by choosing some of these clips. We need to return the minimum number of clips needed, or -1 if it is impossible. Clips can be cut, so using only a portion of a clip is allowed. The official...

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LeetCode 1055: Shortest Way to Form String

Problem Restatement A subsequence of a string is formed by deleting some (or no) characters without changing the order. We are given two strings source and target . We need to form target by choosing the minimum number of subsequences of source and concatenating them. Return the minimum number of subsequences needed, or -1 if it is impossible. The official constraints state that 1 <= source.length, target.length <= 1000 ....

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LeetCode 1081: Smallest Subsequence of Distinct Characters

Problem Restatement We are given a string s . We need to return the lexicographically smallest subsequence of s that contains all distinct characters of s exactly once. The official constraints state that 1 <= s.length <= 1000 and s consists of lowercase English letters. Note: This problem is identical to LeetCode 316 (Remove Duplicate Letters). Input and Output Item Meaning Input String s Output Lexicographically smallest subsequence with each...

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LeetCode 1013: Partition Array Into Three Parts With Equal Sum

Problem Restatement We are given an integer array arr . We need to return true if we can partition the array into three non-empty contiguous parts that each have the same sum. Formally, find indices i and j such that: 0 < i < j < len(arr) sum(arr[:i]) == sum(arr[i:j]) == sum(arr[j:]) If such indices exist, return true . Otherwise return false . The official constraints state that 3 <=...

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LeetCode 1057: Campus Bikes

Problem Restatement We have a campus as a 2D grid. We are given the positions of n workers and m bikes. We need to assign one bike to each worker. We assign bikes greedily: Find the pair (worker, bike) with the smallest Manhattan distance. Assign that bike to that worker. Remove both from consideration. Repeat. If there are ties in distance, pick the smallest worker index, then smallest bike index....

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LeetCode 1090: Largest Values From Labels

Problem Restatement We have n items, each with a value and a label . We want to choose a subset of items to maximize total value, subject to: At most numWanted items can be chosen. At most useLimit items with the same label can be chosen. The official constraints state that n == values.length == labels.length and 1 <= numWanted, useLimit <= n <= 2 * 10^4 . Input and...

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LeetCode 1058: Minimize Rounding Error to Meet Target

Problem Restatement We are given an array of price strings (floating-point) and an integer target . We must round each price either up ( ceil ) or down ( floor ). We need the rounded prices to sum exactly to target . Return the minimum total rounding error, or "-1" if it is impossible. The official constraints state that 1 <= prices.length <= 500 . Input and Output Item Meaning...

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LeetCode 1054: Distant Barcodes

Problem Restatement We are given an array of barcodes. We need to rearrange the barcodes so that no two adjacent barcodes are equal. It is guaranteed that a valid rearrangement always exists. The official constraints state that 1 <= barcodes.length <= 10000 and 1 <= barcodes[i] <= 10000 . Input and Output Item Meaning Input Array barcodes Output Rearranged array with no two adjacent equal elements Function shape: def rearrangeBarcodes(barcodes:...

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LeetCode 1007: Minimum Domino Rotations For Equal Row

Problem Restatement We have n dominoes arranged in a row. For domino i , tops[i] is the value on the top face and bottoms[i] is the value on the bottom face. In one rotation, we can swap the top and bottom of any domino. We need to return the minimum number of rotations so that either all tops are equal or all bottoms are equal. If it is impossible, return...

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LeetCode 1005: Maximize Sum Of Array After K Negations

Problem Restatement We are given an integer array nums and an integer k . In one operation, we choose an index and negate the value at that index. We must perform exactly k operations. We need to return the maximum possible sum of the array after exactly k negations. The official constraints state that 1 <= nums.length <= 10^4 , -100 <= nums[i] <= 100 , and 1 <= k...

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LeetCode 849: Maximize Distance to Closest Person

Problem Restatement We are given an array seats . Each value means: Value Meaning 1 Someone is sitting in this seat 0 This seat is empty Alex wants to choose one empty seat so that the distance to the closest person is as large as possible. Return that maximum distance. There is at least one empty seat and at least one occupied seat. Input and Output Item Meaning Input Binary...

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LeetCode 971: Flip Binary Tree To Match Preorder Traversal

Problem Restatement We are given a binary tree and an array voyage . A flip operation at a node swaps its left and right children. We need to flip the smallest number of nodes so that the preorder traversal of the tree becomes exactly equal to voyage . Preorder traversal visits nodes in this order: root left subtree right subtree If it is possible, return the values of the flipped...

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LeetCode 846: Hand of Straights

Problem Restatement We are given an integer array hand , where each value is written on one card. We are also given an integer groupSize . We need to decide whether all cards can be rearranged into groups such that: Rule Meaning Group size Every group has exactly groupSize cards Consecutive values Cards in each group are consecutive Use all cards Every card must be used exactly once Return True...

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LeetCode 969: Pancake Sorting

Problem Restatement We are given an integer array arr . A pancake flip chooses an integer k and reverses the first k elements of the array. We need to return a sequence of k values that sorts the array in increasing order. Any valid answer is accepted as long as it sorts the array using at most 10 * arr.length flips. The problem constraint gives 1 <= arr.length <= 100...

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LeetCode 921: Minimum Add to Make Parentheses Valid

Problem Restatement We are given a string s containing only parentheses: "(" ")" In one move, we may insert one parenthesis at any position. Return the minimum number of insertions needed to make the string valid. A valid parentheses string is one where every opening parenthesis has a matching closing parenthesis in the correct order. The official statement defines the operation as inserting one parenthesis anywhere in the string. Input...

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LeetCode 968: Binary Tree Cameras

Problem Restatement We are given the root of a binary tree. We may install cameras on tree nodes. A camera at a node can monitor: Its parent Itself Its immediate children Return the minimum number of cameras needed to monitor every node in the tree. The official constraints say the tree has between 1 and 1000 nodes, and every node value is 0 . Input and Output Item Meaning Input...

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LeetCode 948: Bag of Tokens

Problem Restatement We are given an array of token values: tokens and an initial amount of power: power We start with score 0 . Each token may be played at most once, in one of two ways: Play type Requirement Effect Face-up power >= token Lose token power, gain 1 score Face-down score >= 1 Gain token power, lose 1 score We may play any number of tokens in any...

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LeetCode 871: Minimum Number of Refueling Stops

Problem Restatement A car starts at position 0 and needs to reach a destination target miles away. The car starts with startFuel liters of fuel. It consumes: 1 liter of fuel per mile There are gas stations along the way. Each station is represented as: [position, fuel] When the car reaches a station, it may stop and take all fuel from that station. The tank has infinite capacity. Return the...

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LeetCode 775: Global and Local Inversions

Problem Restatement We are given an array nums . The array is a permutation of all integers from 0 to n - 1 . A global inversion is a pair of indices (i, j) such that: i < j nums[i] > nums[j] A local inversion is an index i such that: nums[i] > nums[i + 1] Return True if the number of global inversions is equal to the number of...

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LeetCode 995: Minimum Number of K Consecutive Bit Flips

Problem Restatement We are given a binary array nums and an integer k . A k -bit flip means choosing a contiguous subarray of length k and flipping every bit in it: Bit After flip 0 1 1 0 We need to return the minimum number of k -bit flips required so that the array contains no 0 . If it is impossible, return -1 . The official problem defines...

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LeetCode 870: Advantage Shuffle

Problem Restatement We are given two integer arrays: nums1 nums2 Both arrays have the same length. The advantage of nums1 over nums2 is the number of indices i where: nums1[i] > nums2[i] We may rearrange nums1 in any order. Return any permutation of nums1 that maximizes its advantage over nums2 . Input and Output Item Meaning Input nums1 , the array we may reorder Input nums2 , the fixed comparison...

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LeetCode 945: Minimum Increment to Make Array Unique

Problem Restatement We are given an integer array: nums In one move, we may choose any index and increment that value by 1 . We need to return the minimum number of moves required to make every value in nums unique. The problem guarantees that the answer fits in a 32-bit integer. The official examples include [1,2,2] -> 1 and [3,2,1,2,1,7] -> 6 . Input and Output Item Meaning Input...

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LeetCode 944: Delete Columns to Make Sorted

Problem Restatement We are given an array of equal-length strings: strs Think of the strings as rows of a character matrix. We may delete some columns. A column is valid if its characters are in non-decreasing order from top to bottom. For a column c , we need: strs[0][c] <= strs[1][c] <= strs[2][c] <= ... Return the minimum number of columns that must be deleted so that every remaining column...

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LeetCode 991: Broken Calculator

Problem Restatement We are given two integers: startValue target A broken calculator starts by displaying startValue . It supports only two operations: Operation Effect Double Multiply the current number by 2 Decrement Subtract 1 from the current number We need to return the minimum number of operations needed to display target . The official constraints are: Constraint Value startValue 1 <= startValue <= 10^9 target 1 <= target <= 10^9...

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LeetCode 942: DI String Match

Problem Restatement We are given a string s of length n . Each character is either: "I" or: "D" We need to return any permutation perm of the integers from 0 to n such that: Character Required relation s[i] == "I" perm[i] < perm[i + 1] s[i] == "D" perm[i] > perm[i + 1] If multiple answers exist, any valid answer is accepted. The official statement defines the same reconstruction...

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LeetCode 769: Max Chunks To Make Sorted

Problem Restatement We are given an array arr of length n . The array is a permutation of integers from 0 to n - 1 . We want to split arr into the maximum number of chunks. Then we sort each chunk individually and concatenate the chunks back in the same order. The final result must equal the fully sorted array. Return the largest number of chunks we can make....

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LeetCode 768: Max Chunks To Make Sorted II

Problem Restatement We are given an integer array arr . We want to split it into some number of chunks. Then we sort each chunk individually and concatenate the sorted chunks back in the same order. The final result must equal the fully sorted version of arr . Return the maximum number of chunks we can make. The array may contain duplicate values. Input and Output Item Meaning Input An...

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LeetCode 717: 1-bit and 2-bit Characters

Problem Restatement We are given a binary array: bits The array encodes characters using two rules: Character Type Encoding One-bit character 0 Two-bit character 10 or 11 The array always ends with: 0 We need to determine whether the final character must be a one-bit character. Return: True if the last character is one-bit. Otherwise return: False Input and Output Item Meaning Input Binary array bits Output Whether the last...

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LeetCode 45: Jump Game II

Problem Restatement We are given a 0-indexed integer array nums . We start at index 0 . Each value nums[i] tells us the maximum jump length from index i . From index i , we may jump to any index from i + 1 up to i + nums[i] , as long as the index is inside the array. We need to return the minimum number of jumps needed to...

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LeetCode 625: Minimum Factorization

Problem Restatement We are given a positive integer num . We need to find the smallest positive integer x such that the product of the digits of x equals num . If no such integer exists, return 0 . If the answer does not fit in a 32-bit signed integer, return 0 . The official examples are: num = 48 Output: 68 because: 6 * 8 == 48 Another example:...

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LeetCode 44: Wildcard Matching

Problem Restatement We are given an input string s and a pattern p . The pattern may contain two special wildcard characters: Character Meaning ? Matches any single character * Matches any sequence of characters, including the empty sequence The match must cover the entire input string, not just part of it. The official problem states these wildcard rules directly. For example: s = "aa" p = "a" This returns:...

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LeetCode 624: Maximum Distance in Arrays

Problem Restatement We are given m arrays. Each array is sorted in ascending order. We must pick two integers from two different arrays and compute their distance. The distance between two integers a and b is: abs(a - b) Return the maximum possible distance. For example, from: arrays = [[1, 2, 3], [4, 5], [1, 2, 3]] we can pick 1 from the first array and 5 from the second...

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LeetCode 767: Reorganize String

Problem Restatement We are given a string s . We need to rearrange its characters so that no two adjacent characters are the same. Return any valid rearrangement. If no valid rearrangement exists, return an empty string. The problem allows any correct answer, not one specific output. The official statement says to rearrange the characters so adjacent characters are not equal, or return "" if impossible. Input and Output Item...

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LeetCode 621: Task Scheduler

Problem Restatement We are given a list of CPU tasks. Each task is represented by a capital letter from A to Z . Each task takes exactly one CPU interval. The CPU can do one of two things in each interval: Execute one task. Stay idle. There is also a non-negative integer n . This means that between two executions of the same task, there must be at least n...

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LeetCode 714: Best Time to Buy and Sell Stock with Transaction Fee

Problem Restatement We are given an array prices . prices[i] is the price of a stock on day i . We are also given an integer fee . We may complete as many transactions as we want, but we cannot hold more than one share at the same time. That means we must sell the current stock before buying again. Each completed transaction pays the transaction fee once. Return the...

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LeetCode 765: Couples Holding Hands

Problem Restatement We are given a row of seats. There are n couples, so there are 2n people. People are numbered from 0 to 2n - 1 . Couples are paired in order: Couple People 0 0, 1 1 2, 3 2 4, 5 In general, person x has partner: x ^ 1 This works because: 0 ^ 1 = 1 1 ^ 1 = 0 2 ^ 1 =...

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LeetCode 738: Monotone Increasing Digits

Problem Restatement We are given a non-negative integer n . We need to return the largest integer less than or equal to n whose digits are monotone increasing. A number has monotone increasing digits when every adjacent digit pair satisfies: left_digit <= right_digit For example: 1234 is valid 1119 is valid 332 is not valid The official constraint is: 0 <= n <= 10^9 Input and Output Item Meaning Input...

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LeetCode 763: Partition Labels

Problem Restatement We are given a string s . We need to split it into as many parts as possible so that each letter appears in at most one part. After concatenating all parts in order, we must get the original string back. Return the sizes of the parts. Input and Output Item Meaning Input A string s Output A list of partition sizes Goal Make as many partitions as...

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LeetCode 649: Dota2 Senate

Problem Restatement We are given a string senate . Each character represents one senator: Character Party "R" Radiant "D" Dire The voting process happens in rounds from left to right. On a senator's turn, if they still have voting rights, they can ban one senator from the opposite party. A banned senator loses voting rights for the current and all future rounds. If all remaining senators with voting rights belong...

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LeetCode 936: Stamping The Sequence

Problem Restatement We are given two strings: stamp target Initially, we start with a string made entirely of question marks: "?????" with the same length as target . In one move, we may place the stamp string over any position and overwrite the characters. For example: stamp = "abc" before = "?????" after = "??abc" The goal is to build target . We must return a sequence of stamping positions...

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LeetCode 861: Score After Flipping Matrix

Problem Restatement We are given a binary matrix grid . We may perform any number of operations. Each operation can: Flip one row Flip one column Flipping means changing: 0 -> 1 1 -> 0 After all operations, every row is interpreted as a binary number. The total score is the sum of those binary numbers. We need to return the largest possible score. Input and Output Item Meaning Input...

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LeetCode 646: Maximum Length of Pair Chain

Problem Restatement We are given a list of integer pairs. Each pair looks like: [left, right] A pair: [a, b] can be followed by: [c, d] if: b < c We need to build the longest possible chain of pairs. Return the maximum chain length. The constraints guarantee: left < right for every pair. Input and Output Item Meaning Input List of integer pairs Output Maximum valid chain length Chain...

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LeetCode 910: Smallest Range II

Problem Restatement We are given an integer array nums and an integer k . For every index i , we must either: nums[i] + k or: nums[i] - k Return the minimum possible difference between the maximum and minimum values after all choices are made. Unlike the previous problem, every number must choose exactly one of the two operations. Input and Output Item Meaning Input Integer array nums and integer...

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LeetCode 860: Lemonade Change

Problem Restatement Each lemonade costs $5 . Customers stand in a queue. Each customer buys exactly one lemonade and pays with one bill. The bill can be: 5, 10, or 20 We start with no money. For each customer, we must give the correct change immediately, using only bills received from earlier customers. Return True if we can give correct change to every customer. Otherwise, return False . Input and...

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LeetCode 984: String Without AAA or BBB

Problem Restatement We are given two integers a and b . We need to return any string s such that: Requirement Meaning Length s.length == a + b Count of a s contains exactly a letters 'a' Count of b s contains exactly b letters 'b' Forbidden substring s must not contain "aaa" Forbidden substring s must not contain "bbb" The problem guarantees that a valid answer exists. The constraints...

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LeetCode 670: Maximum Swap

Problem Restatement We are given a non-negative integer num . We may swap two digits at most once. Return the maximum possible value we can get after doing zero or one swap. The official statement asks us to swap two digits at most once to get the maximum valued number. Input and Output Item Meaning Input A non-negative integer num Output The maximum integer possible after at most one digit...

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LeetCode 667: Beautiful Arrangement II

Problem Restatement We are given two integers: Variable Meaning n We must use numbers from 1 to n k Required number of distinct adjacent differences We need to construct an array containing every integer from 1 to n exactly once such that the set of absolute differences between neighboring elements contains exactly k distinct values. For an array: arr the adjacent differences are: |arr[i] - arr[i + 1]| for all...

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LeetCode 782: Transform to Chessboard

Problem Restatement We are given an n x n binary board. Each cell is either 0 or 1 . In one move, we may do one of these operations: Move Meaning Swap two rows Exchange any two complete rows Swap two columns Exchange any two complete columns We need to return the minimum number of moves required to transform the board into a chessboard. A chessboard means no two 4-directionally...

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LeetCode 757: Set Intersection Size At Least Two

Problem Restatement We are given a list of intervals. Each interval is: [start, end] We need to build a set S of integers such that every interval contains at least two numbers from S . Our goal is to make S as small as possible. Return the minimum possible size of S . Input and Output Item Meaning Input A list of intervals [start, end] Output The minimum size of...

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LeetCode 857: Minimum Cost to Hire K Workers

Problem Restatement We are given n workers. Each worker has: Data Meaning quality[i] The quality value of worker i wage[i] The minimum wage worker i must receive We need to hire exactly k workers. The payment must satisfy two rules: Every hired worker must be paid at least their minimum wage. In the hired group, pay must be proportional to quality. That means if one worker has twice the quality...

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LeetCode 807: Max Increase to Keep City Skyline

Problem Restatement We are given an n x n grid. Each value grid[r][c] is the height of a building at row r and column c . We may increase the height of any number of buildings by any amount. We cannot decrease heights. After increasing buildings, the skyline from all four directions must stay the same as the original grid. The task is to return the maximum total increase possible....

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LeetCode 665: Non-decreasing Array

Problem Restatement We are given an integer array nums . We need to check whether it can become non-decreasing by modifying at most one element. A non-decreasing array means every element is less than or equal to the next element. The official statement defines this condition as nums[i] <= nums[i + 1] for every valid index i . Return True if this is possible. Otherwise, return False . Input and...

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LeetCode 881: Boats to Save People

Problem Restatement We are given an array people , where people[i] is the weight of the i th person. We also have an unlimited number of boats. Each boat has weight limit limit . Each boat can carry at most two people at the same time, and their total weight must be at most limit . Return the minimum number of boats needed to carry everyone. The official constraints allow...

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LeetCode 781: Rabbits in Forest

Problem Restatement We are given an array answers . Each value answers[i] is the answer from one rabbit. If a rabbit says x , it means: There are x other rabbits with the same color as me. So that rabbit belongs to a color group of size: x + 1 We need to return the minimum possible number of rabbits in the forest. Some rabbits in the forest may not...

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LeetCode 680: Valid Palindrome II

Problem Restatement We are given a string s . We need to return true if s can become a palindrome after deleting at most one character. Otherwise, return false . The string may also already be a palindrome, because deleting zero characters is allowed. The constraints say 1 <= s.length <= 10^5 , and s contains lowercase English letters. A palindrome reads the same from left to right and right...

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LeetCode 955: Delete Columns to Make Sorted II

Problem Restatement We are given an array strs of strings. All strings have the same length. We may delete any set of column indices. When we delete a column, we delete that character position from every string. After deleting some columns, the remaining strings must be in lexicographic order: strs[0] <= strs[1] <= strs[2] <= ... <= strs[n - 1] Return the minimum number of deleted columns. The official constraints...

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LeetCode 954: Array of Doubled Pairs

Problem Restatement We are given an integer array arr . We want to reorder the array so that for every pair: (arr[2 * i], arr[2 * i + 1]) the second number equals double the first number: arr[2 * i + 1] = 2 * arr[2 * i] Return true if such a reordering is possible. Otherwise, return false . The official constraints are: Constraint Value 2 <= arr.length <=...

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LeetCode 754: Reach a Number

Problem Restatement We start at position 0 on an infinite number line. There is a destination at position target . On move 1 , we must move exactly 1 step. On move 2 , we must move exactly 2 steps. On move 3 , we must move exactly 3 steps. In general, on move i , we must move exactly i steps. For every move, we can choose either direction:...

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LeetCode 575: Distribute Candies

Problem Restatement We are given an integer array candyType . Each integer represents one candy type. Alice has n candies total, where n = len(candyType) . She is allowed to eat exactly n / 2 candies. Return the maximum number of different candy types Alice can eat. The array length is even. The constraints include n == candyType.length , 1 <= n <= 10^4 , n is even, and -10^5...

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LeetCode 659: Split Array into Consecutive Subsequences

Problem Restatement We are given an integer array nums . The array is sorted in non-decreasing order. We need to decide whether we can split all numbers into one or more subsequences such that: Rule Meaning Consecutive Each number is exactly 1 larger than the previous number Minimum length Every subsequence has length at least 3 Use all numbers Every element in nums must be used exactly once Return True...

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LeetCode 630: Course Schedule III

Problem Restatement We are given a list of courses. Each course is represented as: [duration, lastDay] duration is how many days the course takes. lastDay is the latest day by which the course must be finished. We start on day 1 . We can take only one course at a time. We need to return the maximum number of courses we can finish before or on their deadlines. Input and...

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LeetCode 573: Squirrel Simulation

Problem Restatement We are given a garden grid with a tree, a squirrel, and several nuts. The squirrel must collect all nuts and put them under the tree one by one. The squirrel can carry at most one nut at a time. It can move one cell at a time in four directions: up, down, left, and right. Return the minimum total distance the squirrel must move. The problem gives...

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LeetCode 517: Super Washing Machines

Problem Restatement We are given n washing machines in a line. machines[i] is the number of dresses in the i th machine. In one move, we may choose any number of machines. Each chosen machine passes exactly one dress to one adjacent machine at the same time. We need to return the minimum number of moves needed to make every machine contain the same number of dresses. If this is...

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LeetCode 605: Can Place Flowers

Problem Restatement We are given a flowerbed represented by a binary array. Value Meaning 0 Empty plot 1 A flower is already planted Flowers cannot be planted in adjacent plots. We are also given an integer n . We need to determine whether it is possible to plant n new flowers in the flowerbed without violating the no-adjacent-flowers rule. The official problem states that no two flowers can be planted...

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LeetCode 678: Valid Parenthesis String

Problem Restatement We are given a string s . The string contains only three characters: Character Meaning '(' Opening parenthesis ')' Closing parenthesis '*' Wildcard character The wildcard '*' can be treated as one of three choices: Choice Meaning '(' Use it as an opening parenthesis ')' Use it as a closing parenthesis empty string Remove it We need to return true if there is some way to replace every...

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LeetCode 927: Three Equal Parts

Problem Restatement We are given an array arr containing only 0 s and 1 s. We need to split it into three non-empty parts so that all three parts represent the same binary value. Return two indices [i, j] such that: arr[0] ... arr[i] first part arr[i + 1] ... arr[j - 1] second part arr[j] ... arr[n - 1] third part The split must satisfy: i + 1 <...

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LeetCode 976: Largest Perimeter Triangle

Problem Restatement We are given an integer array nums . Each number represents a possible side length of a triangle. We need to choose three lengths that can form a triangle with non-zero area. Among all valid choices, return the largest possible perimeter. If no three lengths can form a valid triangle, return 0 . A valid triangle with side lengths a , b , and c must satisfy the...

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LeetCode 926: Flip String to Monotone Increasing

Problem Restatement We are given a binary string s . Each character is either '0' or '1' . A binary string is monotone increasing when all 0 s come before all 1 s. It may contain only 0 s, only 1 s, or both. Valid examples: "000" "111" "000111" "001111" Invalid examples: "10" "101" "010" We may flip any character: 0 -> 1 1 -> 0 Return the minimum number...

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LeetCode 826: Most Profit Assigning Work

Problem Restatement We are given three arrays: Array Meaning difficulty difficulty[i] is the difficulty of job i profit profit[i] is the profit from job i worker worker[j] is the maximum difficulty worker j can handle Each worker can do at most one job. A job can be used more than once. This is important. If three workers all choose the same job, we count that job's profit three times. If...

Practice › LeetCode › LeetCode (archived) › LeetCode 07xx ›

LeetCode 751: IP to CIDR

Problem Restatement We are given a starting IPv4 address ip and an integer n . We need to cover exactly n consecutive IP addresses starting from ip . The answer should be a list of CIDR blocks with the smallest possible length. A CIDR block looks like this: "123.45.67.89/20" The number after / is the prefix length. A larger prefix length means a smaller block. For example, /32 covers exactly...

Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 502: IPO

Problem Restatement We are given n projects. Each project has: Array Meaning profits[i] The pure profit gained after finishing project i capital[i] The minimum capital needed to start project i We start with capital w . We can finish at most k distinct projects. After finishing a project, its profit is added to our capital. We need to return the maximum final capital possible after choosing at most k projects....

Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 561: Array Partition

Problem Restatement We are given an integer array nums containing 2n integers. We need to divide all numbers into n pairs: (a1, b1), (a2, b2), ..., (an, bn) For each pair, we take the smaller number: min(ai, bi) Return the maximum possible sum of these minimum values. The constraints are 1 <= n <= 10^4 , nums.length == 2 * n , and -10^4 <= nums[i] <= 10^4 . The...

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LeetCode 555: Split Concatenated Strings

Problem Restatement We are given an array of strings strs . We can concatenate the strings into a loop. For each string, we may use it normally or reversed. The strings must stay in the same order as given. After forming the loop, we choose one cut point. Cutting the loop turns it into a normal string. Our goal is to return the lexicographically largest possible string. The input strings...

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LeetCode 527: Word Abbreviation

Problem Restatement We are given an array of distinct lowercase words. For each word, we need to return its minimal unique abbreviation, while keeping the output in the same order as the input. The abbreviation starts with a prefix, then the number of abbreviated middle characters, then the last character. If the abbreviation is not shorter than the original word, we keep the original word. For example: "internal" -> "i6l"...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 421: Maximum XOR of Two Numbers in an Array

Problem Restatement We are given an integer array nums . Return the maximum value of: nums[i] ^ nums[j] where ^ means bitwise XOR. The indices may be the same according to the source statement: 0 <= i <= j < n Using the same element gives XOR value 0 , so it never hurts the maximum when there are at least two useful values. The source constraints are: 1 <=...

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LeetCode 397: Integer Replacement

Problem Restatement We are given a positive integer n . We need to turn n into 1 using the fewest operations. The allowed operations are: Case Operation n is even Replace n with n / 2 n is odd Replace n with either n + 1 or n - 1 Return the minimum number of operations needed. For example: n = 8 The best path is: 8 -> 4 ->...

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LeetCode 324: Wiggle Sort II

Problem Restatement We are given an integer array nums . Rearrange it in-place so that: nums[0] < nums[1] > nums[2] < nums[3] ... This alternating pattern is called wiggle order. The official problem guarantees that a valid answer exists. The follow-up asks for O(n) average time and O(1) extra space. Input and Output Item Meaning Input Integer array nums Output Rearrange nums in-place Wiggle rule nums[0] < nums[1] > nums[2]...

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LeetCode 420: Strong Password Checker

Problem Restatement We are given a string password . Return the minimum number of steps needed to make it strong. A strong password must satisfy all three rules: Rule Requirement Length At least 6 characters and at most 20 characters Character types At least one lowercase letter, one uppercase letter, and one digit Repetition No three same characters in a row In one step, we may: Insert one character. Delete...

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LeetCode 321: Create Maximum Number

Problem Restatement We are given two arrays of digits: nums1 nums2 They represent two numbers. We are also given an integer k . We need to create the maximum possible number of length k by taking digits from the two arrays. Rules: We may take digits from both arrays. We must take exactly k digits total. The relative order of digits taken from the same array must be preserved. Return...

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LeetCode 418: Sentence Screen Fitting

Problem Restatement We are given: Value Meaning sentence A list of words rows Number of screen rows cols Number of columns per row We want to place the sentence repeatedly on the screen. Rules: Words must appear in the original order. A word cannot be split across lines. Consecutive words are separated by one space. The sentence repeats cyclically. Return how many complete times the sentence fits on the screen....

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LeetCode 316: Remove Duplicate Letters

Problem Restatement We are given a string s containing lowercase English letters. We need to remove duplicate letters so that every distinct letter appears exactly once. Among all valid results, return the lexicographically smallest one. The official constraints are: Constraint Value s.length 1 <= s.length <= 10^4 Characters Lowercase English letters This problem is also the same as LeetCode 1081, Smallest Subsequence of Distinct Characters. ( github.com ) Input and...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 122: Best Time to Buy and Sell Stock II

Problem Restatement We are given an array prices , where prices[i] is the stock price on day i . We may buy and sell the stock multiple times, but we can hold at most one share at a time. That means we must sell before buying again. We need to return the maximum profit possible. For example: prices = [7, 1, 5, 3, 6, 4] The best strategy is: buy...

Practice › LeetCode › LeetCode (archived) › LeetCode 00xx ›

LeetCode 68: Text Justification

Problem Restatement We are given a list of words and an integer maxWidth . We need to format the words into lines of exactly maxWidth characters. The rules are: Pack as many words as possible into each line. Each line must have exactly maxWidth characters. For normal lines, spaces should be distributed as evenly as possible between words. If spaces cannot divide evenly, the left gaps get more spaces than...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 410: Split Array Largest Sum

Problem Restatement We are given an integer array nums and an integer k . We must split nums into exactly k non-empty subarrays. Each subarray must be contiguous. Among the k subarrays, each has a sum. We want to minimize the largest of those sums. Return that minimized largest sum. The official examples include nums = [7,2,5,10,8], k = 2 , whose answer is 18 , and nums = [1,2,3,4,5],...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 135: Candy

Problem Restatement There are n children standing in a line. Each child has a rating given by the integer array ratings . We need to give candies to the children under two rules: Each child must get at least one candy. A child with a higher rating than an adjacent neighbor must get more candies than that neighbor. Return the minimum total number of candies needed. The constraints include 1...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 409: Longest Palindrome

Problem Restatement We are given a string s . The string contains lowercase and uppercase English letters. We may rearrange the letters in any order. Return the length of the longest palindrome that can be built using those letters. Letters are case-sensitive, so: "A" != "a" The problem asks for the length only, not the palindrome itself. The constraints are 1 <= s.length <= 2000 , and the string contains...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 134: Gas Station

Problem Restatement There are n gas stations arranged in a circle. At station i : Array Meaning gas[i] Amount of gas we can fill at station i cost[i] Gas needed to travel from station i to station i + 1 The last station connects back to station 0 . We start with an empty tank at one station of our choice. The tank has unlimited capacity. Return the starting station...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 435: Non-overlapping Intervals

Problem Restatement We are given an array of intervals. Each interval has a start and an end: [start, end] We need to remove the minimum number of intervals so that the remaining intervals do not overlap. Two intervals that only touch at an endpoint do not overlap. For example: [1, 2] [2, 3] These can both remain, because the first interval ends exactly when the second interval starts. The official...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 484: Find Permutation

Problem Restatement We are given a string s made only of two characters: Character Meaning I The next number must be greater D The next number must be smaller We need to return the lexicographically smallest permutation of numbers from 1 to n , where: n = len(s) + 1 The permutation must match the pattern in s . For each index i : Pattern Required relation s[i] == "I"...

Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 358: Rearrange String k Distance Apart

Problem Restatement We are given a non-empty lowercase string s and an integer k . We need to rearrange the characters of s so that the same characters are at least distance k from each other. If this is possible, return any valid rearranged string. If this is impossible, return an empty string "" . For example, if character a appears at index i , then the next a can...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 280: Wiggle Sort

Problem Restatement We are given an unsorted integer array nums . We need to reorder it in-place so that it follows this pattern: nums[0] <= nums[1] >= nums[2] <= nums[3] >= nums[4] ... So the values should alternate between low and high. The problem asks us to modify nums directly and return nothing. The input is guaranteed to have at least one valid answer. Input and Output Item Meaning Input...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 406: Queue Reconstruction by Height

Problem Restatement We are given a list of people. Each person is represented as: [h, k] where: Value Meaning h Person height k Number of people in front of this person whose height is greater than or equal to h We must reconstruct the original queue. Return the queue in any valid order. Input and Output Item Meaning Input A list of pairs [h, k] Output The reconstructed queue Height...

Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 334: Increasing Triplet Subsequence

Problem Restatement We are given an integer array nums . Return true if there exists an increasing subsequence of length 3 . That means we need indices: i < j < k such that: nums[i] < nums[j] < nums[k] The elements do not need to be consecutive. They only need to appear in increasing index order. The problem asks for: Requirement Value Time complexity O(n) Extra space O(1) Input and...

Practice › LeetCode › LeetCode (archived) › LeetCode 00xx ›

LeetCode 55: Jump Game

Problem Restatement We are given an integer array nums . We start at index 0 . Each value nums[i] tells us the maximum number of steps we can jump forward from index i . We need to return true if we can reach the last index. Otherwise, return false . The official constraints are 1 <= nums.length <= 10^4 and 0 <= nums[i] <= 10^5 . Input and Output Item...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 455: Assign Cookies

Problem Restatement We are given two arrays: g s The array g stores the greed factor of each child. The array s stores the size of each cookie. A child i is content if we give them one cookie j such that: s[j] >= g[i] Each child can get at most one cookie. Each cookie can be used at most once. We need to return the maximum number of content...

Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 330: Patching Array

Problem Restatement We are given a sorted positive integer array nums and an integer n . We may add new numbers to nums . These added numbers are called patches. After patching, every number in the range [1, n] must be formable as the sum of some elements from the array. Return the minimum number of patches required. The array is sorted in ascending order, and n can be as...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 179: Largest Number

Problem Restatement We are given a list of non-negative integers nums . We need to arrange the numbers so that, when they are joined together, they form the largest possible number. The answer may be very large, so we return it as a string instead of an integer. The official problem states this same requirement: arrange non-negative integers to form the largest number and return it as a string. Input...

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LeetCode 452: Minimum Number of Arrows to Burst Balloons

Problem Restatement We are given a list of balloons. Each balloon is represented by an interval: [xstart, xend] This means the balloon covers every horizontal position from xstart to xend , inclusive. An arrow is shot vertically upward from some x-coordinate x . The arrow bursts a balloon if: xstart <= x <= xend One arrow can burst many balloons if their intervals all contain the same x-coordinate. We need...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 402: Remove K Digits

Problem Restatement We are given a string num representing a non-negative integer and an integer k . We must remove exactly k digits from num . After removing those digits, the remaining digits must stay in their original relative order. Return the smallest possible integer as a string. The result should not contain leading zeroes. If all digits are removed, or the remaining number becomes empty after removing leading zeroes,...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 252: Meeting Rooms

Problem Restatement We are given a list of meeting time intervals. Each interval contains: [start, end] A person can attend all meetings only if none of the meetings overlap. We need to return: True if all meetings can be attended False if at least two meetings overlap Two meetings overlap when one meeting starts before another meeting finishes. Input and Output Item Meaning Input A list of meeting intervals Output...

Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 376: Wiggle Subsequence

Problem Restatement We are given an integer array nums . A wiggle sequence is a sequence where the differences between neighboring numbers strictly alternate between positive and negative. For example: [1, 7, 4, 9, 2, 5] The differences are: [6, -3, 5, -7, 3] The signs alternate: positive, negative, positive, negative, positive So this is a wiggle sequence. We need to return the length of the longest wiggle subsequence. A...

Practice › LeetCode › LeetCode (archived) › LeetCode 00xx ›

LeetCode 12: Integer to Roman

Problem Restatement We are given an integer num . We need to convert it into a Roman numeral string. Roman numerals use seven base symbols: Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 The input satisfies: 1 <= num <= 3999 The LeetCode statement also defines the subtractive forms: Value Roman 4 IV 9 IX 40 XL 90 XC 400 CD 900...

Practice › LeetCode › LeetCode (archived) › LeetCode 00xx ›

LeetCode 11: Container With Most Water

Problem Restatement We are given an integer array height . There are n vertical lines. The i th line has endpoints: (i, 0) (i, height[i]) Choose two lines. Together with the x-axis, they form a container. The amount of water the container can hold depends on: the distance between the two lines the shorter of the two heights The goal is to return the maximum amount of water any pair...

Programming › Algorithm Cookbook › Chapter 1. Foundations ›

1.13 Greedy Choices

A greedy algorithm builds a solution by making one locally best choice at a time. It does not reconsider earlier choices. This makes greedy algorithms simple and fast, but also easy to get wrong. The main difficulty is proof: you must show that each local choice can be part of some globally optimal solution. Greedy algorithms work when the problem has structure that makes local progress safe. A choice is...

#greedy

Codeforces Round 1091 (Div. 2) and CodeCraft 26

CF 2217E - Definitely Larger

CF 2217D - Flip the Bit (Hard Version)

CF 2217B - Flip the Bit (Easy Version)

Codeforces Round 1090 (Div. 4)

CF 2218D - The 67th OEIS Problem

14.14 Graph Greedy

14.22 Greedy Algorithm Design Checklist

14.3 Matroids Overview

14.10 Prefix Constraints

14.12 Priority Queue Greedy

14.17 Greedy Data Structure Design

14.26 Chapter Summary

14.13 Two-Pointer Greedy

14.11 Sorting Plus Greedy

14.7 Fractional Knapsack

14.1 Greedy Choice Property

14.8 Job Sequencing with Deadlines

14.5 Activity Selection

14.16 String Greedy

14.9 Minimum Refueling Stops

Chapter 14. Greedy Algorithms

14.2 Exchange Arguments

14.19 Counterexamples

14.18 Local vs Global Optimum

14.15 Greedy Scheduling Patterns

14.4 Interval Scheduling

14.25 Exercises

14.6 Huffman Coding

14.20 Proving Greedy Algorithms

14.21 Complexity Analysis

14.23 Case Studies

14.24 Advanced Greedy Techniques

CF 2227D - Palindromex

CF 2225B - Alternating String

CF 2227E - It All Went Sideways

CF 2226E - Mental Monumental (Hard Version)

CF 2227F - It Just Keeps Going Sideways

Codeforces Round 1095 (Div. 2)

CF 2226A - Disturbing Distribution

CF 2226B - Everything Everywhere

Educational Codeforces Round 189 (Rated for Div. 2)

CF 2227B - Party Monster

CF 2225F - String Cutting

CF 2222B - Artistic Balance Tree

Spectral::Cup 2026 Round 1 (Codeforces Round 1094, Div. 1 + Div. 2)

CF 2226D - Reserved Reversals

CF 2226C - Mental Monumental (Easy Version)

Codeforces Round 1096 (Div. 3)

CF 2225C - Red-Black Pairs

LeetCode 3675 - Minimum Operations to Transform String

LeetCode 3633 - Earliest Finish Time for Land and Water Rides I

LeetCode 3600 - Maximize Spanning Tree Stability with Upgrades

LeetCode 3576 - Transform Array to All Equal Elements

CF 1966A - Card Exchange

CF 1956D - Nene and the Mex Operator

CF 1967A - Permutation Counting

Codeforces Round 934 (Div. 2)

CF 1942C1 - Bessie's Birthday Cake (Easy Version)

CF 1950F - 0, 1, 2, Tree!

CF 1956C - Nene's Magical Matrix

Codeforces Round 940 (Div. 2) and CodeCraft-23

CF 1946C - Tree Cutting

CF 1976E - Splittable Permutations

CF 482A - Diverse Permutation

CF 1974A - Phone Desktop

CF 1974G - Money Buys Less Happiness Now

CF 1973B - Cat, Fox and the Lonely Array

CF 1951F - Inversion Composition

CF 1951I - Growing Trees

CF 1975A - Bazoka and Mocha's Array

CF 1975D - Paint the Tree

CF 1957B - A BIT of a Construction

CF 1951D - Buying Jewels

CF 1976F - Remove Bridges

CF 1955C - Inhabitant of the Deep Sea

CF 1956E2 - Nene vs. Monsters (Hard Version)

CF 490E - Restoring Increasing Sequence

CF 1949B - Charming Meals