#leetcode

LeetCode 3310 - Remove Methods From Project

LeetCode Problem 3310 Difficulty: 🟡 Medium Topics: Depth-First Search, Breadth-First Search, Graph Theory Solution Understood. For any TAOCP Volume 1 exercise you provide, I will write the solution in the style of a rigorous solution manual: Use Knuth's notation and terminology from the relevant section. State precisely what is to be proved or computed. Justify every algebraic manipulation, combinatorial argument, and algorithmic step. Omit unnecessary exposition and motivational commentary. Present...

LeetCode 3158 - Find the XOR of Numbers Which Appear Twice

LeetCode Problem 3158 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding This problem asks us to find all numbers in the array that appear exactly twice and compute the bitwise XOR of those numbers. The input is an integer array nums . The problem guarantees that every value appears either once or twice, never more than twice. Our task is not to count how many duplicate...

LeetCode 3004 - Maximum Subtree of the Same Color

LeetCode Problem 3004 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding We are given a rooted tree with n nodes, where node 0 is the root. The input edges describes the tree structure. Each entry edges[i] = [u, v] indicates that there is an undirected edge between nodes u and v . Since the problem guarantees that the graph is a tree rooted at node...

LeetCode 3670 - Maximum Product of Two Integers With No Common Bits

LeetCode Problem 3670 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding We the objective is to maximize the product rather than count pairs.

LeetCode 3660 - Jump Game IX

LeetCode Problem 3660 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine, for each position in an array nums , the maximum value that can be reached by making a series of jumps under strict rules. From any index i , we can jump forward to an index j > i only if nums[j] < nums[i] , or jump backward to an index...

LeetCode 3761 - Minimum Absolute Distance Between Mirror Pairs

LeetCode Problem 3761 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math Solution Problem Understanding We are given an integer array nums . A pair of indices (i, j) is called a mirror pair if: i < j reverse(nums[i]) == nums[j] The operation reverse(x) reverses the decimal digits of x and removes any leading zeros that appear after reversal. For example: reverse(12) = 21 reverse(120) = 21 reverse(1000) = 1 The...

LeetCode 3774 - Absolute Difference Between Maximum and Minimum K Elements

LeetCode Problem 3774 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding The problem asks us to calculate the absolute difference between the sum of the k largest elements and the sum of the k smallest elements in a given array nums . In other words, we first need to identify the k smallest values, sum them up, then identify the k largest values, sum them, and finally compute the...

LeetCode 3738 - Longest Non-Decreasing Subarray After Replacing at Most One Element

LeetCode Problem 3738 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding == 5 # already non-decreasing edge cases assert Solution().

LeetCode 3438 - Find Valid Pair of Adjacent Digits in String

LeetCode Problem 3438 Difficulty: 🟢 Easy Topics: Hash Table, String, Counting Solution Problem Understanding The problem gives us a string s containing only digits from '1' to '9' . We need to find the first adjacent pair of digits that satisfies two conditions. First, the two digits in the pair must be different. A pair like "22" or "55" is never valid. Second, each digit in the pair must appear...

LeetCode 3430 - Maximum and Minimum Sums of at Most Size K Subarrays

LeetCode Problem 3430 Difficulty: 🔴 Hard Topics: Array, Math, Stack, Monotonic Stack Solution Problem Understanding We are remains efficient even at the maximum constraint limit.

LeetCode 3431 - Minimum Unlocked Indices to Sort Nums

LeetCode Problem 3431 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding We are given two arrays of equal both required ranges are empty and the impossibility condition cannot occur.

LeetCode 3421 - Find Students Who Improved

LeetCode Problem 3421 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding This This ensures that performance in one subject never affects another subject's result.

LeetCode 3394 - Check if Grid can be Cut into Sections

LeetCode Problem 3394 Difficulty: 🟡 Medium Topics: Array, Sorting Solution

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...

LeetCode 3671 - Sum of Beautiful Subsequences

LeetCode Problem 3671 Difficulty: 🔴 Hard Topics: Array, Math, Binary Indexed Tree, Number Theory Solution Problem Understanding Let a subsequence of nums be any sequence multiples. citeturn0search1turn0search2 check whether it is strictly increasing, compute its GCD, and add that GCD to the answer. This is correct because every valid subsequence is examined exactly once. Unfortunately, there are 2^n subsequences. Even for `n = um queries efficiently. citeturn0search1turn0 Force | O(2^n...

LeetCode 3669 - Balanced K-Factor Decomposition

LeetCode Problem 3669 Difficulty: 🟡 Medium Topics: Math, Backtracking, Number Theory Solution Problem Understanding We are given two integers, n and k . Our goal is to split n into exactly k positive integers whose product is equal to n . Among all valid decompositions, we want the one where the difference between the largest number and the smallest number is as small as possible. Since the maximum difference between...

LeetCode 3639 - Minimum Time to Activate String

LeetCode Problem 3639 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding We are given a string s of length n and a permutation array order . At time t = 0 , the character at index order[0] is replaced with '*' . At time t = 1 , the character at index order[1] is also replaced with '*' . This process continues until every position has eventually been...

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...

LeetCode 3634 - Minimum Removals to Balance Array

LeetCode Problem 3634 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sliding Window, Sorting Solution Problem Understanding The problem asks us to transform a given integer array nums into a balanced array with the minimum number of removals . An array is defined as balanced if its maximum element does not exceed k times its minimum element. Formally, for array A , it must satisfy: $$\max(A) \le k \cdot \min(A)$$ We...

LeetCode 3631 - Sort Threats by Severity and Exploitability

LeetCode Problem 3631 Difficulty: 🟡 Medium Topics: Array, Sorting Solution Problem Understanding We are asked to sort a list of threats according to a computed score. Each threat is represented as a 3-element array [IDi, sevi, expi] , where IDi is a unique identifier, sevi is the severity, and expi is the exploitability. The score of a threat is defined as: score = 2 × sevi + expi The required...

LeetCode 3621 - Number of Integers With Popcount-Depth Equal to K I

LeetCode Problem 3621 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming, Bit Manipulation, Combinatorics Solution Problem Understanding This problem asks us to count integers x in the range [1, n] such that the popcount-depth of x is exactly k . The popcount-depth is defined via a sequence p0, p1, ... where p0 = x and pi+1 = popcount(pi) for all i ≥ 0 . The popcount of a number is the...

LeetCode 3616 - Number of Student Replacements

LeetCode Problem 3616 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding The problem models a simple selection process among students arriving one by one. Each student has a rank, where a smaller rank value represents a better student. The first arriving student is automatically selected. As additional students arrive, we compare their rank against the rank of the currently selected student. If the new student has a strictly better...

LeetCode 3615 - Longest Palindromic Path in Graph

LeetCode Problem 3615 Difficulty: 🔴 Hard Topics: String, Dynamic Programming, Bit Manipulation, Graph Theory, Bitmask Solution Problem Understanding We are given an undirected graph with n ≤ 14 vertices. Each vertex has a character label. We may choose any simple path in the graph, meaning a sequence of adjacent vertices in which no vertex is visited more than once. If the labels encountered along that path form a palindrome, the...

LeetCode 3613 - Minimize Maximum Component Cost

LeetCode Problem 3613 Difficulty: 🟡 Medium Topics: Binary Search, Union-Find, Graph Theory, Sorting Solution Let's dive into a full technical guide for LeetCode 3613 following your requested structure. Problem Understanding The problem presents an undirected, connected graph with n nodes and weighted edges. Each edge connects two nodes and has a weight representing its "cost." You are allowed to remove edges to create up to k connected components. The cost...

LeetCode 3610 - Minimum Number of Primes to Sum to Target

LeetCode Problem 3610 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Number Theory Solution Problem Understanding The problem requires us to determine the minimum number of prime numbers from the first m primes whose sum equals n . A multiset is allowed, meaning each prime may be chosen multiple times. The input integers n and m specify the target sum and the number of primes available, respectively. The output is...

LeetCode 3608 - Minimum Time for K Connected Components

LeetCode Problem 3608 Difficulty: 🟡 Medium Topics: Binary Search, Union-Find, Graph Theory, Sorting Solution Minimum Time for K Connected Components Problem Understanding We are given an undirected graph with n vertices and a list of edges. Every edge has an associated removal time timei . The graph evolves over time. At time t , every edge whose removal time satisfies timei <= t has already been removed. All edges with...

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...

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...

LeetCode 3637 - Trionic Array I

LeetCode Problem 3637 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding We are given an integer array nums and need to determine whether it can be divided into three consecutive segments that follow a very specific pattern: A strictly increasing segment. A strictly decreasing segment. A strictly increasing segment. More formally, we must find two indices p and q such that: 0 < p < q < n - 1...

LeetCode 3602 - Hexadecimal and Hexatrigesimal Conversion

LeetCode Problem 3602 Difficulty: 🟢 Easy Topics: Math, String Solution Problem Understanding The numbers that still fit in standard integer types; the algorithm scales logarithmically with digit count.

LeetCode 3649 - Number of Perfect Pairs

LeetCode Problem 3649 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Sorting Solution Problem Understanding We are given an integer array nums and must count how many index pairs (i, j) with i < j are perfect . For each pair, let: a = nums[i] b = nums[j] The pair is considered perfect if both of the following conditions hold: min(|a - b|, |a + b|) <= min(|a|, |b|) max(|a...

LeetCode 3644 - Maximum K to Sort a Permutation

LeetCode Problem 3644 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution

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...

LeetCode 3629 - Minimum Jumps to Reach End via Prime Teleportation

LeetCode Problem 3629 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Breadth-First Search, Number Theory Solution Problem Understanding The problem gives an integer array nums of length n , where each index represents a node in a graph. The task is to start at index 0 and reach index n - 1 in the minimum number of moves. From any index i , there are two types of moves. The...

LeetCode 3890 - Integers With Multiple Sum of Two Cubes

LeetCode Problem 3890 Difficulty: 🟡 Medium Topics: Hash Table, Sorting, Counting, Enumeration Solution Problem Understanding The problem asks us to find all integers x less than or equal to a given integer n such that x can be expressed as the sum of cubes of two positive integers in at least two distinct ways . A “distinct way” means that the pairs (a, b) used to form x are different,...

LeetCode 3792 - Sum of Increasing Product Blocks

LeetCode Problem 3792 Difficulty: 🟡 Medium Topics: Math, Simulation Solution Problem Understanding The problem defines a sequence of blocks, where each block contains the product of a consecutive range of integers. The pattern works as follows: The 1st block contains only 1 The 2nd block contains 2 × 3 The 3rd block contains 4 × 5 × 6 The 4th block contains 7 × 8 × 9 × 10 Notice...

LeetCode 3889 - Mirror Frequency Distance

LeetCode Problem 3889 Difficulty: 🟡 Medium Topics: Hash Table, String, Counting Solution LeetCode 3889 - Mirror Frequency Distance Problem Understanding We are given a string s containing only lowercase English letters ( a-z ) and digits ( 0-9 ). Each character has a corresponding mirror character: Letters are mirrored across the alphabet. a ↔ z b ↔ y c ↔ x and so on. Digits are mirrored across the digit...

LeetCode 3875 - Construct Uniform Parity Array I

LeetCode Problem 3875 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to determine if it is possible to construct a new array nums2 of the same length as nums1 where all elements are either all odd or all even. For each element nums2[i] , we can either copy the corresponding element from nums1[i] directly, or we can set it as the difference between nums1[i] and...

LeetCode 3791 - Number of Balanced Integers in a Range

LeetCode Problem 3791 Difficulty: 🔴 Hard Topics: Dynamic Programming Solution Here is the full, detailed technical solution guide for LeetCode 3791 - Number of Balanced Integers in a Range, following your requested structure. Problem Understanding The problem asks us to count all integers between low and high inclusive that are balanced . An integer is defined as balanced if it meets two conditions. First, it must have at least two...

LeetCode 3885 - Design Event Manager

LeetCode Problem 3885 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to design an EventManager class that manages a set of events, each identified by a unique eventId and associated with a priority . The manager must support two primary operations: updating the priority of an active event and retrieving the highest-priority active event, with ties broken by...

LeetCode 3790 - Smallest All-Ones Multiple

LeetCode Problem 3790 Difficulty: 🟡 Medium Topics: Hash Table, Math Solution Problem Understanding This problem asks us to find the smallest positive integer composed entirely of the digit 1 that is divisible by a given integer k . The input k is guaranteed to be between 2 and 100,000. We are asked not for the number itself, but for the number of digits in this number, which simplifies the task...

LeetCode 3884 - First Matching Character From Both Ends

LeetCode Problem 3884 Difficulty: 🟢 Easy Topics: Two Pointers, String Solution LeetCode 3884 - First Matching Character From Both Ends Problem Understanding This problem gives us a string s of length n consisting of lowercase English letters. For every index i , we compare two characters: The character at position i , which is s[i] The character at the mirrored position from the other end, which is s[n - i...

LeetCode 3882 - Minimum XOR Path in a Grid

LeetCode Problem 3882 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Matrix Solution LeetCode 3882 - Minimum XOR Path in a Grid Problem Understanding We are given an m × n grid of integers. Starting from the top-left cell (0, 0) , we must reach the bottom-right cell (m - 1, n - 1) by moving only right or down. For every path, we compute its cost as the...

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...

LeetCode 3883 - Count Non Decreasing Arrays With Given Digit Sums

LeetCode Problem 3883 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem asks us to compute the number of non-decreasing arrays of integers where each integer satisfies a specific digit sum constraint. Specifically, we are given an array digitSum of length n , where digitSum[i] represents the required sum of digits for the i -th element in the array. We must construct arrays arr of...

LeetCode 3880 - Minimum Absolute Difference Between Two Values

LeetCode Problem 3880 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 3880 - Minimum Absolute Difference Between Two Values Problem Understanding The problem gives us an integer array nums where every element is guaranteed to be one of three values: 0 , 1 , or 2 . A pair of indices (i, j) is considered valid when: nums[i] == 1 nums[j] == 2 For every valid pair, we compute the...

LeetCode 3788 - Maximum Score of a Split

LeetCode Problem 3788 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem asks us to maximize a "score" obtained by splitting an integer array nums at a valid index i . For each split index i , the score is calculated as the sum of all elements from the beginning of the array up to i ( prefixSum ) minus the minimum value in the remaining elements...

LeetCode 3881 - Direction Assignments with Exactly K Visible People

LeetCode Problem 3881 Difficulty: 🟡 Medium Topics: Math, Combinatorics Solution LeetCode 3881 - Direction Assignments with Exactly K Visible People Problem Understanding We are given n people standing in a line, indexed from 0 to n - 1 . Each person independently chooses one of two directions: 'L' means the person is visible only to people on their right. 'R' means the person is visible only to people on their...

LeetCode 3786 - Total Sum of Interaction Cost in Tree Groups

LeetCode Problem 3786 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search Solution I can do this, but I need the actual problem details for LeetCode 3786 - Total Sum of Interaction Cost in Tree Groups to ensure the algorithm, proof, and code are correct. The statement you pasted appears complete, but this problem is recent and correctness matters for a Hard tree problem. I need to verify whether there are...

LeetCode 3878 - Count Good Subarrays

LeetCode Problem 3878 Difficulty: 🔴 Hard Topics: Array, Stack, Bit Manipulation, Monotonic Stack Solution LeetCode 3878 - Count Good Subarrays Problem Understanding We are given an integer array nums , and we must count how many subarrays are good . A subarray is considered good if the bitwise OR of all elements in that subarray is equal to at least one element that appears inside the same subarray. Suppose a...

LeetCode 3879 - Maximum Distinct Path Sum in a Binary Tree

LeetCode Problem 3879 Difficulty: 🟡 Medium Topics: Hash Table, Tree, Depth-First Search, Binary Tree Solution Problem Understanding The problem asks us to find the maximum sum of node values along a path in a binary tree such that all values in the path are distinct . The path can start and end at any node, does not need to pass through the root, and must consist of connected nodes. Each...

LeetCode 3784 - Minimum Deletion Cost to Make All Characters Equal

LeetCode Problem 3784 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Enumeration Solution Problem Understanding The problem asks us to minimize the total cost of deleting characters from a string such that the resulting string contains only one unique character . We are given a string s of length n and an array cost of the same length, where cost[i] is the cost of deleting the character s[i] . The...

LeetCode 3877 - Minimum Removals to Achieve Target XOR

LeetCode Problem 3877 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution LeetCode 3877 - Minimum Removals to Achieve Target XOR Problem Understanding We are given an array nums and a target value target . We may remove any subset of elements from the array, including removing none of them or even removing all of them. After performing the removals, the remaining elements form a new array. The bitwise...

LeetCode 3782 - Last Remaining Integer After Alternating Deletion Operations

LeetCode Problem 3782 Difficulty: 🔴 Hard Topics: Math, Recursion Solution Before I write the full guide, I want to confirm one critical detail because the examples appear inconsistent with the stated operations. The statement says: Operation 1: Starting from the left, delete every second number Example transforms [1,2,3,4,5,6,7,8] → [1,3,5,7] This means it is deleting positions 2,4,6,8 and keeping odd positions . However, for Operation 2 on [1,3,5,7] , the...

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...

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...

LeetCode 3876 - Construct Uniform Parity Array II

LeetCode Problem 3876 Difficulty: 🟡 Medium Topics: Array, Math Solution Problem Understanding The problem asks us to determine whether we can construct a new array nums2 from a given array nums1 of distinct integers such that all elements in nums2 have the same parity (all even or all odd). For each index i , we have two options: we can either take nums1[i] directly, or subtract any other element nums1[j]...

LeetCode 3869 - Count Fancy Numbers in a Range

LeetCode Problem 3869 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming Solution LeetCode 3869 - Count Fancy Numbers in a Range Problem Understanding We are given two integers l and r , and we must count how many integers in the inclusive range [l, r] are fancy . The definition of a fancy number is based on the concept of a good number. A number is good if its digits form...

LeetCode 3779 - Minimum Number of Operations to Have Distinct Elements

LeetCode Problem 3779 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem gives us an integer array nums and defines a very specific operation: in one move, we remove the first three elements of the current array. If fewer than three elements remain, we remove everything that is left. We continue performing this operation until one of two conditions becomes true: The array becomes empty. The remaining...

LeetCode 3873 - Maximum Points Activated with One Addition

LeetCode Problem 3873 Difficulty: 🔴 Hard Topics: Array, Hash Table, Union-Find Solution Problem Understanding The problem is asking us to simulate a chain reaction of activations on a set of 2D points. Each point is defined by its (x, y) coordinates and all points are distinct. When a point is activated, any point sharing the same x coordinate or y coordinate becomes activated as well. This activation propagates recursively: newly...

LeetCode 3872 - Longest Arithmetic Sequence After Changing At Most One Element

LeetCode Problem 3872 Difficulty: 🟡 Medium Topics: Array, Enumeration Solution Problem Understanding The problem requires us to find the longest arithmetic subarray from a given array of integers nums if we are allowed to modify at most one element. An arithmetic subarray is a contiguous sequence in which the difference between consecutive elements is constant. The input, nums , is an integer array of length between 4 and 105, and...

LeetCode 3871 - Count Commas in Range II

LeetCode Problem 3871 Difficulty: 🟡 Medium Topics: Math Solution LeetCode 3871 - Count Commas in Range II Problem Understanding The problem asks us to count the total number of commas that appear when writing every integer from 1 through n using standard comma-separated number formatting. In standard formatting, commas are inserted every three digits from the right: 1 through 999 contain no commas. 1,000 through 999,999 contain one comma each....

LeetCode 3870 - Count Commas in Range

LeetCode Problem 3870 Difficulty: 🟢 Easy Topics: Math Solution LeetCode 3870 - Count Commas in Range Problem Understanding The problem asks us to count how many commas appear when writing every integer from 1 through n using standard number formatting. In standard formatting, commas are inserted every three digits from the right side of the number. For example: 999 contains 0 commas. 1,000 contains 1 comma. 12,345 contains 1 comma....

LeetCode 3778 - Minimum Distance Excluding One Maximum Weighted Edge

LeetCode Problem 3778 Difficulty: 🟡 Medium Topics: — Solution Problem Understanding We are given a connected, weighted, undirected graph with n nodes numbered from 0 to n - 1 . Every edge is represented as [u, v, w] , meaning there is a bidirectional edge between nodes u and v with positive weight w . The objective is to find the minimum cost path from node 0 to node n...

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...

LeetCode 3867 - Sum of GCD of Formed Pairs

LeetCode Problem 3867 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Simulation, Number Theory Solution LeetCode 3867 - Sum of GCD of Formed Pairs Problem Understanding We are given an integer array nums of length n . For every index i , we first compute: mxi , the maximum value among nums[0...i] prefixGcd[i] = gcd(nums[i], mxi) This creates a new array called prefixGcd . After that, we sort prefixGcd in...

LeetCode 3866 - First Unique Even Element

LeetCode Problem 3866 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to find the first even integer in an array that appears exactly once . In other words, we need to traverse the array and identify even numbers, count their occurrences, and return the earliest one that occurs only a single time. If there is no such even number, we return -1 ....

LeetCode 3775 - Reverse Words With Same Vowel Count

LeetCode Problem 3775 Difficulty: 🟡 Medium Topics: Two Pointers, String, Simulation Solution Problem Understanding The problem requires processing a string s consisting of lowercase English words separated by single spaces. The first task is to count the number of vowels in the first word . Then, for each subsequent word in the string, if the word has the same number of vowels as the first word, it should be reversed....

LeetCode 3865 - Reverse K Subarrays

LeetCode Problem 3865 Difficulty: 🟡 Medium Topics: Array, Two Pointers Solution Problem Understanding The problem asks us to take an integer array nums of length n and divide it into k contiguous subarrays of equal length, then reverse each subarray individually. The resulting array should preserve the order of the subarrays but reflect the reversal within each one. For example, if nums = [1,2,4,3,5,6] and k = 3 , each...

LeetCode 3864 - Minimum Cost to Partition a Binary String

LeetCode Problem 3864 Difficulty: 🔴 Hard Topics: String, Divide and Conquer, Prefix Sum Solution LeetCode 3864 - Minimum Cost to Partition a Binary String Problem Understanding We are given a binary string s , where each character represents whether an element is sensitive: '1' means the element is sensitive. '0' means the element is not sensitive. The entire string initially forms one segment. Every segment has a storage cost that...

LeetCode 3773 - Maximum Number of Equal Length Runs

LeetCode Problem 3773 Difficulty: 🟡 Medium Topics: Hash Table, String, Counting Solution Problem Understanding The problem asks us to analyze a string s consisting of lowercase English letters and identify runs , which are contiguous sequences of identical characters that cannot be extended further. For example, in "aaabaaa" , the runs are "aaa" , "b" , and "aaa" . The goal is to select runs that all have the same...

LeetCode 3862 - Find the Smallest Balanced Index

LeetCode Problem 3862 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution LeetCode 3862 - Find the Smallest Balanced Index Problem Understanding We are given an integer array nums , and we need to find the smallest index i that satisfies a special balance condition. For a given index i : The left sum is the sum of all elements strictly before i , that is, nums[0] + nums[1] + ......

LeetCode 3772 - Maximum Subgraph Score in a Tree

LeetCode Problem 3772 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding The problem asks us to compute, for each node in a tree, the maximum score of a connected subgraph that includes that node. The tree is represented as an undirected graph with n nodes and n - 1 edges. Each node has a value indicating whether it is good ( 1 ) or bad...

LeetCode 3863 - Minimum Operations to Sort a String

LeetCode Problem 3863 Difficulty: 🟡 Medium Topics: String Solution Problem Understanding This problem is asking us to determine the minimum number of substring sort operations needed to make a string s sorted in non-descending alphabetical order . We are allowed to sort any substring of s , but we cannot sort the entire string at once. The goal is to find the smallest number of operations to achieve a fully...

LeetCode 3771 - Total Score of Dungeon Runs

LeetCode Problem 3771 Difficulty: 🟡 Medium Topics: Array, Binary Search, Prefix Sum Solution Problem Understanding The problem describes a dungeon with n rooms, where entering room i reduces your health points by damage[i] . After taking this damage, if your remaining health is at least requirement[i] , you earn 1 point for that room. You can start your dungeon run at any room j (1-indexed) and proceed through the rest...

LeetCode 3860 - Unique Email Groups

LeetCode Problem 3860 Difficulty: 🟡 Medium Topics: Array, Hash Table, String Solution LeetCode 3860 - Unique Email Groups Problem Understanding This problem asks us to determine how many distinct email groups exist after applying a specific normalization process to every email address. Each email consists of two parts separated by the '@' character: The local name appears before '@' . The domain name appears after '@' . Before comparing emails,...

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...

LeetCode 3769 - Sort Integers by Binary Reflection

LeetCode Problem 3769 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding This problem asks us to sort an array of positive integers based on a transformation called binary reflection . The binary reflection of a number is obtained by converting the number to its binary representation, reversing the order of the bits (ignoring leading zeros), and then interpreting the resulting binary string as a decimal integer. For example, the...

LeetCode 3857 - Minimum Cost to Split into Ones

LeetCode Problem 3857 Difficulty: 🟡 Medium Topics: Math, Dynamic Programming Solution LeetCode 3857 - Minimum Cost to Split into Ones Problem Understanding We are given a single integer n . Starting with this integer, we repeatedly perform split operations until every resulting piece is equal to 1 . A split operation takes some integer x and divides it into two positive integers a and b such that: $$a + b...

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...

LeetCode 3856 - Trim Trailing Vowels

LeetCode Problem 3856 Difficulty: 🟢 Easy Topics: String Solution LeetCode 3856 - Trim Trailing Vowels Problem Understanding This problem asks us to remove all vowels that appear at the end of a given string. The input is a string s consisting only of lowercase English letters. A vowel is defined as one of the five characters: 'a' , 'e' , 'i' , 'o' , or 'u' . The goal is...

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,...

LeetCode 3766 - Minimum Operations to Make Binary Palindrome

LeetCode Problem 3766 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Bit Manipulation Solution Problem Understanding This problem asks us to find the minimum number of increment or decrement operations needed to convert each number in a list into a binary palindrome . A binary palindrome is a number whose binary representation reads the same forwards and backwards once leading zeros are removed. For example, the number 5 in...

LeetCode 3855 - Sum of K-Digit Numbers in a Range

LeetCode Problem 3855 Difficulty: 🔴 Hard Topics: Math, Divide and Conquer, Combinatorics, Number Theory Solution LeetCode 3855 - Sum of K-Digit Numbers in a Range Problem Understanding We are given three integers l , r , and k . For every digit position, we may independently choose any digit from the inclusive range [l, r] . We then form all possible numbers consisting of exactly k digits. A key detail...

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...

LeetCode 3852 - Smallest Pair With Different Frequencies

LeetCode Problem 3852 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution LeetCode 3852 - Smallest Pair With Different Frequencies Problem Understanding This problem gives us an integer array nums and asks us to find a pair of distinct values [x, y] that satisfies two conditions: x < y The frequency of x in the array is different from the frequency of y . Among all valid pairs, we must...

LeetCode 3853 - Merge Close Characters

LeetCode Problem 3853 Difficulty: 🟡 Medium Topics: Hash Table, String Solution Problem Understanding The problem asks us to repeatedly merge close, equal characters in a string s . A character pair is considered close if the distance between their indices is at most k . When a merge occurs, the right character is removed and the string is updated immediately. Merges are performed one at a time, always choosing the...

LeetCode 3759 - Count Elements With at Least K Greater Values

LeetCode Problem 3759 Difficulty: 🟡 Medium Topics: Array, Binary Search, Divide and Conquer, Sorting, Quickselect Solution Problem Understanding The problem asks us to count how many elements in an array have at least k values that are strictly greater than them. More concretely, for every element nums[i] , we need to determine how many numbers in the array are larger than nums[i] . If that count is at least k...

LeetCode 3850 - Count Sequences to K

LeetCode Problem 3850 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Memoization, Number Theory Solution LeetCode 3850 - Count Sequences to K Problem Understanding We start with a value val = 1 and process the array from left to right. For every element nums[i] , we must choose exactly one of three actions: Multiply the current value by nums[i] Divide the current value by nums[i] Do nothing Division is exact...

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...

LeetCode 3758 - Convert Number Words to Digits

LeetCode Problem 3758 Difficulty: 🟡 Medium Topics: String, Trie Solution Problem Understanding The problem asks us to parse a string s that contains lowercase English letters and may include concatenated English words representing digits from 0 to 9. Our goal is to extract all valid number words in order and convert them to their corresponding digit, producing a string of digits. The string must be processed from left to right...

LeetCode 3847 - Find the Score Difference in a Game

LeetCode Problem 3847 Difficulty: 🟡 Medium Topics: Array, Simulation Solution LeetCode 3847 - Find the Score Difference in a Game Problem Understanding This problem describes a game played over a sequence of rounds. The array nums represents the points awarded in each game, where nums[i] is the number of points available during game i . There are exactly two players. At the beginning: The first player is active. The second...

LeetCode 3757 - Number of Effective Subsequences

LeetCode Problem 3757 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics Solution Here’s a complete, detailed technical guide for LeetCode 3757 - Number of Effective Subsequences , following your formatting instructions exactly. Problem Understanding The problem gives us an array of integers, nums , and asks us to determine the number of effective subsequences . The strength of the array is defined as the bitwise OR of...

LeetCode 3848 - Check Digitorial Permutation

LeetCode Problem 3848 Difficulty: 🟡 Medium Topics: Math, Counting Solution Problem Understanding The problem asks us to determine whether any permutation of the digits of a given integer n forms a digitorial number. A digitorial number is defined as a number equal to the sum of the factorials of its digits. For instance, 145 is digitorial because $1! + 4! + 5! = 145$. The input is a single integer...

LeetCode 3846 - Total Distance to Type a String Using One Finger

LeetCode Problem 3846 Difficulty: 🟡 Medium Topics: Hash Table, String Solution LeetCode 3846 - Total Distance to Type a String Using One Finger Problem Understanding This problem asks us to calculate the total finger movement required to type a given lowercase string on a special keyboard layout using only one finger. The keyboard is arranged as: q w e r t y u i o p a s d f...

LeetCode 3844 - Longest Almost-Palindromic Substring

LeetCode Problem 3844 Difficulty: 🟡 Medium Topics: Two Pointers, String, Dynamic Programming Solution LeetCode 3844 - Longest Almost-Palindromic Substring Problem Understanding We are given a string s consisting of lowercase English letters. We must find the length of the longest substring that is almost-palindromic . A substring is almost-palindromic if we can remove exactly one character from that substring and the remaining characters form a palindrome. The key detail is...

LeetCode 3756 - Concatenate Non-Zero Digits and Multiply by Sum II

LeetCode Problem 3756 Difficulty: 🟡 Medium Topics: Math, String, Prefix Sum Solution Please provide the official LeetCode problem statement or confirm the exact problem details for LeetCode 3756 - Concatenate Non-Zero Digits and Multiply by Sum II . I want to avoid hallucinating the intended optimal approach because this appears to be a very recent/problem-specific question, and correctness matters for the full guide, code, worked examples, and complexity analysis. The...

LeetCode 3754 - Concatenate Non-Zero Digits and Multiply by Sum I

LeetCode Problem 3754 Difficulty: 🟢 Easy Topics: Math Solution Problem Understanding The problem asks us to process an integer n and construct a new number using only its non-zero digits. These digits must remain in the same order in which they originally appear. After constructing this new integer x , we calculate the sum of its digits and then return the product: $$x \times \text{sum of digits of } x$$...

LeetCode 3845 - Maximum Subarray XOR with Bounded Range

LeetCode Problem 3845 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Queue, Sliding Window, Prefix Sum, Monotonic Queue Solution Problem Understanding The problem asks us to find a subarray of a given non-negative integer array nums such that the difference between the maximum and minimum elements of the subarray does not exceed a given integer k . Once such a subarray is chosen, we compute the XOR of all its...

LeetCode 3750 - Minimum Number of Flips to Reverse Binary String

LeetCode Problem 3750 Difficulty: 🟢 Easy Topics: Math, Two Pointers, String, Bit Manipulation Solution Problem Understanding The problem gives us a positive integer n , and asks us to work with its binary representation. First, we convert n into a binary string s without leading zeros. Then, we compute the reverse of that binary string. Our goal is to determine the minimum number of bit flips required so that s...

LeetCode 3842 - Toggle Light Bulbs

LeetCode Problem 3842 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting, Simulation Solution LeetCode 3842 - Toggle Light Bulbs Problem Understanding The problem gives us an array bulbs , where each value represents a light bulb number between 1 and 100 . Initially, there are exactly 100 light bulbs, and every bulb is turned off. We process the array from left to right. For each value bulbs[i] : If that...

LeetCode 3841 - Palindromic Path Queries in a Tree

LeetCode Problem 3841 Difficulty: 🔴 Hard Topics: Array, String, Divide and Conquer, Tree, Segment Tree Solution LeetCode 3841: Palindromic Path Queries in a Tree Problem Understanding We are given a tree with n nodes. Each node stores a lowercase English letter. The tree is undirected and connected, so there is exactly one simple path between any two nodes. The problem supports two kinds of operations: Update Change the character assigned...

LeetCode 3839 - Number of Prefix Connected Groups

LeetCode Problem 3839 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting Solution LeetCode 3839: Number of Prefix Connected Groups Problem Understanding The problem gives us an array of strings words and an integer k . Two words are considered prefix-connected if they share exactly the same first k characters and they come from different indices in the array. A connected group is defined as a set of words where...

LeetCode 3838 - Weighted Word Mapping

LeetCode Problem 3838 Difficulty: 🟢 Easy Topics: Array, String, Simulation Solution Problem Understanding The problem provides two inputs: words , an array of lowercase English strings. weights , an array of 26 integers where weights[i] represents the weight assigned to the letter corresponding to index i ( 0 -> 'a' , 1 -> 'b' , ..., 25 -> 'z' ). For every word, we must compute its total weight by...

LeetCode 3840 - House Robber V

LeetCode Problem 3840 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem is a variation of the classic House Robber problem, but with an additional constraint: each house has a color, and you cannot rob two adjacent houses if they share the same color. We are given two arrays nums and colors of length n . The array nums represents the amount of money at each house,...

LeetCode 3837 - Delayed Count of Equal Elements

LeetCode Problem 3837 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding The problem requires computing a delayed count for each element in an array nums . For an index i , the delayed count is defined as the number of later elements (indices j > i + k ) that are equal to nums[i] . In simpler terms, for each element, we want to count how many...

LeetCode 3836 - Maximum Score Using Exactly K Pairs

LeetCode Problem 3836 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution LeetCode 3836 - Maximum Score Using Exactly K Pairs Problem Understanding We are given two arrays, nums1 of length n and nums2 of length m , along with an integer k . Our goal is to choose exactly k pairs of indices: $$(i_1, j_1), (i_2, j_2), \dots, (i_k, j_k)$$ such that: $$i_1 < i_2 < \dots < i_k$$ and...

LeetCode 3835 - Count Subarrays With Cost Less Than or Equal to K

LeetCode Problem 3835 Difficulty: 🟡 Medium Topics: Array, Queue, Monotonic Queue Solution LeetCode 3835 - Count Subarrays With Cost Less Than or Equal to K Problem Understanding We are given an array nums and an integer k . For every subarray nums[l..r] , its cost is defined as: $$(\max(nums[l..r]) - \min(nums[l..r])) \times (r-l+1)$$ The first part measures the range of values inside the subarray, while the second part measures the...

LeetCode 3834 - Merge Adjacent Equal Elements

LeetCode Problem 3834 Difficulty: 🟡 Medium Topics: Array, Stack, Simulation Solution Problem Understanding The problem asks us to repeatedly merge adjacent equal elements in an integer array nums until no further merges are possible. Specifically, if two consecutive elements are equal, we replace them with their sum. The key points are that we always pick the leftmost pair for merging, and after each merge, the array size decreases by one....

LeetCode 3833 - Count Dominant Indices

LeetCode Problem 3833 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 3833 - Count Dominant Indices Problem Understanding The problem gives us an integer array nums of length n . For every index i , we must determine whether the element nums[i] is dominant . An index is considered dominant if its value is strictly greater than the average of all elements to its right. In other words, for index...

LeetCode 3829 - Design Ride Sharing System

LeetCode Problem 3829 Difficulty: 🟡 Medium Topics: Hash Table, Design, Queue, Data Stream Solution Problem Understanding The problem asks us to design a ride sharing system that manages both riders and drivers as they enter the system, and to match them in a first-come, first-served order. The system must track riders who are waiting for rides, drivers who are available, and support canceling rider requests. Inputs include rider and driver...

LeetCode 3749 - Evaluate Valid Expressions

LeetCode Problem 3749 Difficulty: 🔴 Hard Topics: Hash Table, Math, String, Divide and Conquer, Stack Solution Problem Understanding The problem presents a simplified version of evaluating nested mathematical expressions in string format. The input expression is either a single integer literal, which may be negative, or a nested operation of the form op(a,b) where op is one of the four basic arithmetic operations: add , sub , mul , or...

LeetCode 3832 - Find Users with Persistent Behavior Patterns

LeetCode Problem 3832 Difficulty: 🔴 Hard Topics: — Solution LeetCode 3832 - Find Users with Persistent Behavior Patterns Problem Understanding The activity table records user actions. Each row contains a user_id , the action_date , and the specific action performed on that date. The primary key is (user_id, action_date, action) , which guarantees that the exact same action for the same user on the same day cannot appear twice. However,...

LeetCode 3746 - Minimum String Length After Balanced Removals

LeetCode Problem 3746 Difficulty: 🟡 Medium Topics: String, Stack, Counting Solution Before I write the full guide, I want to verify one detail because this appears to be a very new LeetCode problem and correctness matters here. The examples strongly suggest a key simplification: the answer may reduce to the absolute difference between the total number of 'a' and 'b' characters, because any balanced substring has net contribution 0 ,...

LeetCode 3828 - Final Element After Subarray Deletions

LeetCode Problem 3828 Difficulty: 🟡 Medium Topics: Array, Math, Brainteaser, Game Theory Solution Problem Understanding We are given an integer array nums . Two players, Alice and Bob, repeatedly remove a contiguous subarray from the current array. The only restriction is that the removed subarray cannot be the entire current array, so after every move at least one element remains. After a subarray is removed, the remaining elements are concatenated...

LeetCode 3830 - Longest Alternating Subarray After Removing At Most One Element

LeetCode Problem 3830 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Enumeration Solution Problem Understanding The problem asks us to find the longest alternating subarray in a given integer array nums , where a subarray is defined as consecutive elements. A subarray is considered alternating if the sequence of comparisons between adjacent elements strictly alternates between less-than and greater-than. Formally, for a subarray nums[l..r] , it must satisfy either: nums[l] <...

LeetCode 3741 - Minimum Distance Between Three Equal Elements II

LeetCode Problem 3741 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem asks us to find three distinct indices (i, j, k) such that the values at those positions are identical: nums[i] == nums[j] == nums[k] Among all such valid triples, we must compute the minimum possible distance , where the distance is defined as: abs(i - j) + abs(j - k) + abs(k - i) If...

LeetCode 3803 - Count Residue Prefixes

LeetCode Problem 3803 Difficulty: 🟢 Easy Topics: Hash Table, String Solution Problem Understanding The problem asks us to analyze prefixes of a string s and count how many of them satisfy a specific condition. A prefix is any substring that starts at the first character and extends to some point in the string. For a prefix to be a residue , the number of distinct characters in that prefix must...

LeetCode 3826 - Minimum Partition Score

LeetCode Problem 3826 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Dynamic Programming, Queue, Prefix Sum, Monotonic Queue Solution LeetCode 3826 - Minimum Partition Score Problem Understanding We are given an array nums and must divide it into exactly k contiguous subarrays. For every subarray, we first compute its sum: $$\text{sumArr} = \sum \text{elements in the subarray}$$ Its value is then defined as: $$\text{value} = \frac{\text{sumArr} \cdot (\text{sumArr}+1)}{2}$$ The score...

LeetCode 3739 - Count Subarrays With Majority Element II

LeetCode Problem 3739 Difficulty: 🔴 Hard Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Merge Sort, Prefix Sum Solution Here’s a complete, detailed technical solution guide for LeetCode 3739 - Count Subarrays With Majority Element II following your requested format. Problem Understanding The problem asks us to count the number of contiguous subarrays in which a given target element is the majority element . A majority element is one...

LeetCode 3827 - Count Monobit Integers

LeetCode Problem 3827 Difficulty: 🟢 Easy Topics: Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to count Monobit integers from 0 to n . A Monobit integer is one where all bits in its binary representation are the same. This means there are only two possibilities for a valid Monobit integer: all zeros or all ones. For instance, 0 ( 0b0 ), 1 ( 0b1 ), 3 (...

LeetCode 3737 - Count Subarrays With Majority Element I

LeetCode Problem 3737 Difficulty: 🟡 Medium Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Merge Sort, Counting, Prefix Sum Solution Here is a comprehensive, detailed reference guide for LeetCode 3737 - Count Subarrays With Majority Element I , following your formatting requirements exactly. Problem Understanding The problem provides an integer array nums and a target integer. The goal is to count the number of subarrays in which the target...

LeetCode 3825 - Longest Strictly Increasing Subsequence With Non-Zero Bitwise AND

LeetCode Problem 3825 Difficulty: 🟡 Medium Topics: Array, Binary Search, Bit Manipulation, Enumeration Solution Problem Understanding This problem asks us to find the longest strictly increasing subsequence (LIS) in a given integer array nums , with the additional constraint that the bitwise AND of all elements in the subsequence must be non-zero . In simpler terms, among all sequences you can extract from nums where each number is strictly larger...

LeetCode 3736 - Minimum Moves to Equal Array Elements III

LeetCode Problem 3736 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to determine the minimum number of moves required to make every element in an integer array equal. A move consists of selecting one element and increasing it by exactly 1 . We are not allowed to decrease values, and we can only increment elements. In other words, we need to choose a target value...

LeetCode 3823 - Reverse Letters Then Special Characters in a String

LeetCode Problem 3823 Difficulty: 🟢 Easy Topics: Two Pointers, String, Simulation Solution LeetCode 3823 - Reverse Letters Then Special Characters in a String Problem Understanding This problem gives us a string s that contains two types of characters: Lowercase English letters ( 'a' to 'z' ) Special characters from the set "!@#$%^&*()" We must perform two independent reversals, in a specific order. First, we extract all lowercase letters from the...

LeetCode 3733 - Minimum Time to Complete All Deliveries

LeetCode Problem 3733 Difficulty: 🟡 Medium Topics: Math, Binary Search Solution This is a long, structured reference document. To make sure I target the correct problem and avoid producing an incorrect guide, I want to verify one thing first: Can you confirm the exact LeetCode problem number/title? “LeetCode 3733 - Minimum Time to Complete All Deliveries” does not appear to match a known standard problem in my current knowledge, and...

LeetCode 3731 - Find Missing Elements

LeetCode Problem 3731 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting Solution Problem Understanding This problem asks us to reconstruct a missing sequence of integers from a partially incomplete array. We are given an integer array nums containing unique values , and we know an important fact: the array originally contained every integer in a continuous range , but some numbers were removed. Even though some values are missing, the...

LeetCode 3822 - Design Order Management System

LeetCode Problem 3822 Difficulty: 🟡 Medium Topics: Hash Table, Design Solution LeetCode 3822 - Design Order Management System Problem Understanding This problem asks us to implement a small in-memory order management system that supports four operations on trading orders. Each order has three attributes: orderId , a unique identifier orderType , either "buy" or "sell" price , an integer value When an order is added, it becomes active. Orders remain...

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...

LeetCode 3821 - Find Nth Smallest Integer With K One Bits

LeetCode Problem 3821 Difficulty: 🔴 Hard Topics: Math, Bit Manipulation, Combinatorics Solution Problem Understanding This problem asks us to find the nth smallest positive integer whose binary representation contains exactly k ones . In other words, we are working with numbers that, when written in binary, have a specific number of bits set to 1 . The input consists of two integers: n representing the ordinal position in the sequence...

LeetCode 3728 - Stable Subarrays With Equal Boundary and Interior Sum

LeetCode Problem 3728 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to count stable subarrays in an integer array capacity . A subarray capacity[l..r] is stable if it satisfies two conditions: its length is at least 3, and the first and last elements are each equal to the sum of the elements strictly between them. In other words, for a subarray [a0,...

LeetCode 3819 - Rotate Non Negative Elements

LeetCode Problem 3819 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding The problem asks us to rotate only the non-negative elements of an integer array nums to the left by k positions in a cyclic manner, while leaving all negative elements fixed in their original positions. In other words, the negative numbers act as "anchors" in the array, and the rotation affects only the positive numbers and zeros. After...

LeetCode 3725 - Count Ways to Choose Coprime Integers from Rows

LeetCode Problem 3725 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Matrix, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to determine how many ways we can choose exactly one number from each row of a given m x n matrix such that the greatest common divisor (GCD) of all chosen numbers is 1. In other words, we need to count all valid combinations of one element per...

LeetCode 3817 - Good Indices in a Digit String

LeetCode Problem 3817 Difficulty: 🟡 Medium Topics: Math, String Solution LeetCode 3817 - Good Indices in a Digit String Problem Understanding We are given a string s consisting only of decimal digits. The string length is n , and indices are zero-based. For every index i , we need to determine whether i is a good index . An index is considered good if there exists a substring ending exactly...

LeetCode 3818 - Minimum Prefix Removal to Make Array Strictly Increasing

LeetCode Problem 3818 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem asks us to process an integer array nums and determine the minimum length of a prefix that we can remove so that the remaining array becomes strictly increasing. A prefix is any number of contiguous elements starting from the beginning of the array, including possibly zero elements (meaning we may not need to remove anything). A strictly...

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...

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...

LeetCode 3722 - Lexicographically Smallest String After Reverse

LeetCode Problem 3722 Difficulty: 🟡 Medium Topics: Two Pointers, Binary Search, Enumeration Solution Problem Understanding The problem asks us to find the lexicographically smallest string after performing exactly one reverse operation on a contiguous prefix or suffix of a given string s . The string consists only of lowercase English letters and can have a length up to 1000 characters. In other words, we can either reverse the first k...

LeetCode 3815 - Design Auction System

LeetCode Problem 3815 Difficulty: 🟡 Medium Topics: Hash Table, Design, Heap (Priority Queue), Ordered Set Solution LeetCode 3815 - Design Auction System Problem Understanding This problem asks us to design a real time auction system that supports inserting, updating, removing, and querying bids efficiently. Each bid is uniquely identified by the pair (userId, itemId) . A user may have at most one active bid for a particular item. If addBid...

LeetCode 3721 - Longest Balanced Subarray II

LeetCode Problem 3721 Difficulty: 🔴 Hard Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Prefix Sum Solution Problem Understanding The problem requires us to find the length of the longest subarray in an integer array nums where the count of distinct even numbers equals the count of distinct odd numbers . A subarray is a contiguous section of the array, and “distinct” means that duplicate values are counted only...

LeetCode 3813 - Vowel-Consonant Score

LeetCode Problem 3813 Difficulty: 🟢 Easy Topics: String, Simulation Solution LeetCode 3813 - Vowel-Consonant Score Problem Understanding The problem asks us to compute a score for a given string s . The string may contain lowercase English letters, spaces, and digits. We need to count two quantities: v , the number of vowels in the string. c , the number of consonants in the string. The vowels are exactly the...

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...

LeetCode 3717 - Minimum Operations to Make the Array Beautiful

LeetCode Problem 3717 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Here is the complete, detailed technical solution guide for LeetCode 3717 - Minimum Operations to Make the Array Beautiful following your exact formatting rules. Problem Understanding The problem asks us to transform an integer array nums into a beautiful array . An array is considered beautiful if every element (except the first) is divisible by its previous element. Formally,...

LeetCode 3812 - Minimum Edge Toggles on a Tree

LeetCode Problem 3812 Difficulty: 🔴 Hard Topics: Tree, Depth-First Search, Graph Theory, Topological Sort, Sorting Solution LeetCode 3812 - Minimum Edge Toggles on a Tree Problem Understanding We are given a tree with n nodes and n - 1 edges. Every node has a binary color represented by the strings start and target . An operation consists of selecting an edge and toggling both of its endpoints. If a node...

LeetCode 3714 - Longest Balanced Substring II

LeetCode Problem 3714 Difficulty: 🟡 Medium Topics: Hash Table, String, Prefix Sum Solution Problem Understanding The problem gives us a string s that contains only three possible characters: 'a' , 'b' , and 'c' . We must find the longest substring where every distinct character in that substring appears the same number of times . A key detail is that the condition only applies to distinct characters present in the...

LeetCode 3712 - Sum of Elements With Frequency Divisible by K

LeetCode Problem 3712 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to compute the sum of all elements in the array whose total frequency is divisible by a given integer k . To understand the requirement clearly, we need to focus on two important details: First, we must determine how many times each number appears in the array. This is the element's frequency...

LeetCode 3811 - Number of Alternating XOR Partitions

LeetCode Problem 3811 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation Solution LeetCode 3811 - Number of Alternating XOR Partitions Problem Understanding We are given an array nums and two distinct target XOR values, target1 and target2 . A partition divides the array into contiguous, non-empty blocks. Every element must belong to exactly one block, and the blocks must cover the entire array. The partition is considered...

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...

LeetCode 3710 - Maximum Partition Factor

LeetCode Problem 3710 Difficulty: 🔴 Hard Topics: Array, Binary Search, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory Solution Problem Understanding The problem asks us to split a set of n points in a 2D Cartesian plane into exactly two non-empty groups, such that the minimum Manhattan distance among all pairs of points within each group (the partition factor) is maximized. The Manhattan distance between points [xi, yi] and [xj, yj]...

LeetCode 3808 - Find Emotionally Consistent Users

LeetCode Problem 3808 Difficulty: 🟡 Medium Topics: — Solution LeetCode 3808 - Find Emotionally Consistent Users Problem Understanding This problem asks us to analyze user reactions and determine which users exhibit a strong preference for a particular reaction type. The input is a table named reactions , where each row represents a reaction given by a user to a specific content item. The pair (user_id, content_id) is unique, which means...

LeetCode 3709 - Design Exam Scores Tracker

LeetCode Problem 3709 Difficulty: 🟡 Medium Topics: Array, Binary Search, Design, Prefix Sum Solution Problem Understanding This problem asks us to design a system that tracks Alice's exam scores over time and efficiently computes the total score for any given time interval. The system must support two operations: recording a new exam with a timestamp and score, and querying the total score of exams between two timestamps inclusive. The input...

LeetCode 3807 - Minimum Cost to Repair Edges to Traverse a Graph

LeetCode Problem 3807 Difficulty: 🟡 Medium Topics: Binary Search, Breadth-First Search, Graph Theory Solution Problem Understanding The problem presents an undirected graph with n nodes labeled from 0 to n-1 and m edges. Each edge has a repair cost, and initially, all edges are damaged. We can spend a certain amount of money to repair all edges whose cost is less than or equal to that amount. After repairing some...

LeetCode 3704 - Count No-Zero Pairs That Sum to N

LeetCode Problem 3704 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming Solution Problem Understanding The problem asks us to count all pairs of positive integers (a, b) such that their sum equals a given integer n and neither a nor b contains the digit 0 in their decimal representation. These integers are called no-zero integers . The input n is guaranteed to be at least 2 and can be as large...

LeetCode 3805 - Count Caesar Cipher Pairs

LeetCode Problem 3805 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, String, Counting Solution LeetCode 3805 - Count Caesar Cipher Pairs Problem Understanding We are given an array words containing n lowercase strings. Every string has the same length m . Two strings are considered similar if we can repeatedly apply the following operation to either string: Shift every character forward by one position in the alphabet. The alphabet wraps...

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...

LeetCode 3702 - Longest Subsequence With Non-Zero Bitwise XOR

LeetCode Problem 3702 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding We are given an integer array nums , and we must determine the maximum possible length of a subsequence whose bitwise XOR is not equal to zero . A subsequence is formed by deleting zero or more elements from the array while preserving the relative order of the remaining elements. Unlike subarrays, subsequences do not need to...

LeetCode 3804 - Number of Centered Subarrays

LeetCode Problem 3804 Difficulty: 🟡 Medium Topics: Array, Hash Table, Enumeration Solution Problem Understanding The problem asks us to count the number of centered subarrays in a given integer array nums . A subarray is called centered if the sum of its elements is equal to at least one element within that subarray . In simpler terms, for every contiguous sequence of numbers in nums , we need to check...

LeetCode 3700 - Number of ZigZag Arrays II

LeetCode Problem 3700 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming Solution Problem Understanding The problem asks us to count the number of arrays of length n where each element is in the range [l, r] , no two consecutive elements are equal, and no three consecutive elements are strictly increasing or strictly decreasing. These arrays are termed ZigZag arrays . In other words, for an array A of length n...

LeetCode 3802 - Number of Ways to Paint Sheets

LeetCode Problem 3802 Difficulty: 🔴 Hard Topics: — Solution Problem Understanding The problem asks us to compute the number of ways to paint n sheets using exactly two distinct colors , subject to constraints on the maximum number of sheets each color can paint. The input consists of an integer n and an array limit of size m , where limit[i] represents the maximum sheets color i can paint. The...

LeetCode 3799 - Word Squares II

LeetCode Problem 3799 Difficulty: 🟡 Medium Topics: Array, String, Backtracking, Sorting, Enumeration Solution LeetCode 3799 - Word Squares II Problem Understanding We are given an array of distinct 4-letter words. Our goal is to construct every valid word square consisting of exactly four different words: top forms the top row. bottom forms the bottom row. left forms the left column. right forms the right column. Since each word has length...

LeetCode 3699 - Number of ZigZag Arrays I

LeetCode Problem 3699 Difficulty: 🔴 Hard Topics: Dynamic Programming, Prefix Sum Solution Here is the complete technical solution guide for LeetCode 3699 - Number of ZigZag Arrays I , formatted exactly according to your specifications. Problem Understanding The problem asks us to count arrays of length n where each element is within the range [l, r] and satisfies the ZigZag constraints. A ZigZag array has two main rules: no two...

LeetCode 3801 - Minimum Cost to Merge Sorted Lists

LeetCode Problem 3801 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Bit Manipulation Solution Problem Understanding We are given between 2 and 12 sorted lists. At any moment we may choose any two existing lists and merge them. If the two lists are $a$ and $b$, the merge cost is $$\operatorname{len}(a)+\operatorname{len}(b)+ \left|\operatorname{median}(a)-\operatorname{median}(b)\right|.$$ After the merge, the two lists disappear and are replaced by their sorted union. The...

LeetCode 3698 - Split Array With Minimum Difference

LeetCode Problem 3698 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution I can write the full detailed guide, but I need to flag one issue first: the problem statement for LeetCode 3698 - Split Array With Minimum Difference appears inconsistent with the provided Go stub and the current LeetCode catalog. Before I produce a rigorous reference-quality solution, I need to confirm the exact problem definition, because there is a high...

LeetCode 3696 - Maximum Distance Between Unequal Words in Array I

LeetCode Problem 3696 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding The problem gives us an array of strings, words , and asks us to find the maximum distance between two indices i and j where the words at those positions are different . More formally, we want to find two indices such that: words[i] != words[j] i < j the value j - i + 1 is as...

LeetCode 3692 - Majority Frequency Characters

LeetCode Problem 3692 Difficulty: 🟢 Easy Topics: Hash Table, String, Counting Solution Problem Understanding The problem asks us to analyze the frequency distribution of characters in a string and identify a particular group of characters based on how often they appear. We are given a string s containing only lowercase English letters. For every distinct character, we first count how many times it appears. Characters with the same count belong...

LeetCode 3685 - Subsequence Sum After Capping Elements

LeetCode Problem 3685 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Dynamic Programming, Sorting Solution Here is a complete, rigorous study companion-style solution guide for LeetCode 3685 - Subsequence Sum After Capping Elements , following your requested format and voice. Problem Understanding We are given an integer array nums of size n and a positive integer k . For any integer x from 1 to n , we define the capped...

LeetCode 3795 - Minimum Subarray Length With Distinct Sum At Least K

LeetCode Problem 3795 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 3795: Minimum Subarray Length With Distinct Sum At Least K Problem Understanding This problem asks us to find the shortest contiguous subarray whose distinct-value sum is at least k . The important detail is that we do not sum all elements in the subarray. Instead, each distinct value contributes to the sum exactly once, regardless of...

LeetCode 3794 - Reverse String Prefix

LeetCode Problem 3794 Difficulty: 🟢 Easy Topics: Two Pointers, String Solution LeetCode 3794 - Reverse String Prefix Problem Understanding This problem gives us a string s and an integer k . Our task is to reverse only the first k characters of the string while leaving the remaining characters unchanged. In other words, we take the substring consisting of the first k characters, reverse its order, and then append the...

LeetCode 3601 - Find Drivers with Improved Fuel Efficiency

LeetCode Problem 3601 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding This problem asks final stage, preserving accuracy during computation and preventing premature rounding errors from affecting averages or comparisons.

LeetCode 3765 - Complete Prime Number

LeetCode Problem 3765 Difficulty: 🟡 Medium Topics: Math, Enumeration, Number Theory Solution LeetCode 3765 - Complete Prime Number Problem Understanding The problem gives us a positive integer num and asks whether it is a Complete Prime Number . A number qualifies as a Complete Prime Number if every prefix and every suffix of its decimal representation is prime. For a number with digits d1 d2 d3 ... dn : Prefixes...

LeetCode 3755 - Find Maximum Balanced XOR Subarray Length

LeetCode Problem 3755 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Prefix Sum Solution LeetCode 3755 - Find Maximum Balanced XOR Subarray Length Problem Understanding This problem asks us to find the longest contiguous subarray that simultaneously satisfies two independent conditions: The bitwise XOR of all elements in the subarray is equal to 0 . The subarray contains an equal number of even and odd elements. We are given...

LeetCode 3742 - Maximum Path Score in a Grid

LeetCode Problem 3742 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem presents a grid of size m x n where each cell contains a value of 0, 1, or 2. Each cell contributes both a score and a cost: a cell with value 0 adds 0 to both score and cost, a cell with value 1 adds 1 to score and 1 to cost, and...

LeetCode 3729 - Count Distinct Subarrays Divisible by K in Sorted Array

LeetCode Problem 3729 Difficulty: 🔴 Hard Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to find the number of distinct subarrays in a sorted array nums such that the sum of elements in the subarray is divisible by a given integer k . A subarray is a contiguous segment of the original array, and two subarrays are considered distinct if their sequences of values differ,...

LeetCode 3584 - Maximum Product of First and Last Elements of a Subsequence

LeetCode Problem 3584 Difficulty: 🟡 Medium Topics: Array, Two Pointers Solution Problem Understanding The problem asks for the maximum possible product of the first and last elements of any subsequence of length m chosen from an integer array nums . A subsequence means we can pick elements in order from the array, not necessarily contiguous, as long as their indices are strictly increasing. However, only the first and last elements...

LeetCode 3718 - Smallest Missing Multiple of K

LeetCode Problem 3718 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem asks us to find the smallest positive multiple of k that is not present in a given integer array nums . In other words, if we consider the infinite sequence of numbers k, 2k, 3k, 4k… , we need to identify the first number in this sequence that does not appear in nums . The...

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...

LeetCode 3583 - Count Special Triplets

LeetCode Problem 3583 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding We are given an integer array nums of length n . We must count the number of index triplets (i, j, k) such that 0 <= i < j < k < n and the middle element nums[j] acts as a generator for both ends through the relation nums[i] = 2 * nums[j] and nums[k] =...

LeetCode 3708 - Longest Fibonacci Subarray

LeetCode Problem 3708 Difficulty: 🟡 Medium Topics: Array Solution LeetCode 3708 - Longest Fibonacci Subarray Problem Understanding The problem gives us an array nums consisting of positive integers and asks us to find the length of the longest contiguous subarray that satisfies the Fibonacci property. A subarray is a contiguous segment of the original array. For a sequence to be considered Fibonacci, every element from the third position onward must...

LeetCode 3703 - Remove K-Balanced Substrings

LeetCode Problem 3703 Difficulty: 🟡 Medium Topics: String, Stack, Simulation Solution LeetCode 3703 - Remove K-Balanced Substrings Problem Understanding We are given a string s consisting only of '(' and ')' , along with an integer k . A substring is considered k-balanced if it is exactly: "(" repeated k times + ")" repeated k times For example: k = 1 → "()" k = 2 → "(())" k =...

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...

LeetCode 3690 - Split and Merge Array Transformation

LeetCode Problem 3690 Difficulty: 🟡 Medium Topics: Array, Hash Table, Breadth-First Search Solution LeetCode 3690 - Split and Merge Array Transformation Problem Understanding The problem gives us two arrays, nums1 and nums2 , of equal length n . We are allowed to repeatedly perform a special operation on nums1 . In a single operation, we choose any contiguous subarray, remove it from its current location, and then insert that entire...

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....

LeetCode 3679 - Minimum Discards to Balance Inventory

LeetCode Problem 3679 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window, Simulation, Counting Solution LeetCode 3679 - Minimum Discards to Balance Inventory Problem Understanding This problem models a stream of arriving items. On each day, exactly one item arrives, and each item has a type represented by an integer. We are given two parameters: w , the size of the sliding window. m , the maximum number of times...

LeetCode 3661 - Maximum Walls Destroyed by Robots

LeetCode Problem 3661 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Sorting Solution LeetCode 3661 - Maximum Walls Destroyed by Robots Problem Understanding This problem takes place on a one dimensional number line. We are given positions of robots and positions of walls. Every robot owns exactly one bullet, and that bullet can be fired either to the left or to the right. A robot located at position robots[i]...

LeetCode 3654 - Minimum Sum After Divisible Sum Deletions

LeetCode Problem 3654 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Prefix Sum Solution LeetCode 3654 - Minimum Sum After Divisible Sum Deletions Problem Understanding This problem gives us an array nums containing positive integers and an integer k . We may repeatedly remove any contiguous subarray whose sum is divisible by k . After each removal, the remaining elements close the gap, meaning the array becomes shorter and...

LeetCode 3642 - Find Books with Polarized Opinions

LeetCode Problem 3642 Difficulty: 🟡 Medium Topics: — Solution Problem Understanding The problem asks us to identify books that exhibit polarized opinions based on reading session ratings. We have two tables: books , which contains metadata about each book including its title, author, genre, and number of pages, and reading_sessions , which records individual reading sessions with a session_rating from 1 to 5. A book qualifies as having polarized opinions...

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...

LeetCode 3569 - Maximize Count of Distinct Primes After Split

LeetCode Problem 3569 Difficulty: 🔴 Hard Topics: Array, Math, Segment Tree, Number Theory Solution Problem Understanding The task asks us to maintain an integer array that is repeatedly updated, and after each update we must determine an optimal split point that maximizes a specific score based on distinct prime values . For any split index $k$, the array is divided into a prefix $[0..k-1]$ and a suffix $[k..n-1]$. We compute...

LeetCode 3568 - Minimum Moves to Clean the Classroom

LeetCode Problem 3568 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding The problem asks us to compute the minimum number of moves a student must make to collect all litter 'L' in a classroom represented as an m x n grid. The student starts at 'S' with a finite energy that decreases by 1 with each step. Cells 'R' allow the student to...

LeetCode 3611 - Find Overbooked Employees

LeetCode Problem 3611 Difficulty: 🟡 Medium Topics: Database Solution LeetCode 3611 - Find Overbooked Employees Problem Understanding This problem asks us to identify employees who spend an excessive amount of their working time in meetings. We are given two tables: The employees table contains employee information, including their unique identifier, name, and department. The meetings table contains meeting attendance records. Each record tells us which employee attended a meeting, on...

LeetCode 3609 - Minimum Moves to Reach Target in Grid

LeetCode Problem 3609 Difficulty: 🔴 Hard Topics: Math Solution Problem Understanding The problem asks us to determine the minimum number of moves to reach a target point (tx, ty) from a starting point (sx, sy) on an infinite 2D grid. The movement rules are specific: from any point (x, y) , you can move either right by max(x, y) units or up by max(x, y) units. That means each move...

LeetCode 3564 - Seasonal Sales Analysis

LeetCode Problem 3564 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding The task asks us to determine the most popular product category for each season based on sales data. We are given two tables: a sales table containing individual transaction records and a products table that maps each product to its category. The goal is to aggregate sales at the category level within each season and then select the top...

LeetCode 3562 - Maximum Profit from Trading Stocks with Discounts

LeetCode Problem 3562 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding We are given a rooted tree of employees, where employee 1 is the CEO and the root of the hierarchy. Each node represents an investment opportunity with a cost today ( present[i] ) and a return tomorrow ( future[i] ). The profit from investing in employee i is therefore future[i] - cost[i] , where...

LeetCode 3595 - Once Twice

LeetCode Problem 3595 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem provides an integer array nums where every element appears exactly three times , except for one element that appears once and one element that appears twice . We are asked to identify these two unique elements and return them as a list, with the element appearing once first and the element appearing twice second. The...

LeetCode 3593 - Minimum Increments to Equalize Leaf Paths

LeetCode Problem 3593 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution LeetCode 3593 - Minimum Increments to Equalize Leaf Paths Problem Understanding We are given a rooted tree with root node 0 . Every node has a cost, and the score of a root-to-leaf path is the sum of the costs of all nodes along that path. We are allowed to increase the cost of any nodes...

LeetCode 3590 - Kth Smallest Path XOR Sum

LeetCode Problem 3590 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Ordered Set Solution Problem Understanding The problem asks us to work with an undirected tree rooted at node 0, where each node has a value vals[i] and a parent par[i] . We are asked to calculate the path XOR sum for each node, which is defined as the XOR of all vals[i] along the path from the root to...

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...

LeetCode 3551 - Minimum Swaps to Sort by Digit Sum

LeetCode Problem 3551 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting Solution Problem Understanding We are given an array nums consisting of distinct positive integers. The task is to reorder this array into a new array sorted by a custom key: the sum of digits of each integer. If two integers have the same digit sum, the smaller integer must appear first among them. The output is not the sorted...

LeetCode 3550 - Smallest Index With Digit Sum Equal to Index

LeetCode Problem 3550 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem requires us to find the smallest index in an integer array nums such that the sum of the digits of the element at that index is equal to the index itself. In other words, for each index i , we calculate the sum of the digits of nums[i] and check if it equals i . If...

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...

LeetCode 3548 - Equal Sum Grid Partition II

LeetCode Problem 3548 Difficulty: 🔴 Hard Topics: Array, Hash Table, Matrix, Enumeration, Prefix Sum Solution Problem Understanding The problem asks us to determine if we can partition a given m x n grid of positive integers into two connected sections by making exactly one horizontal or vertical cut , such that the sums of the two sections are equal or can be made equal by removing at most one cell....

LeetCode 3566 - Partition Array into Two Equal Product Subsets

LeetCode Problem 3566 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Recursion, Enumeration Solution Here’s a detailed technical solution guide for LeetCode 3566 following your formatting rules: Problem Understanding The problem asks us to determine whether a given array of distinct positive integers can be split into two non-empty, disjoint subsets , such that the product of the elements in each subset equals a given target value . Each element of...

LeetCode 3558 - Number of Ways to Assign Edge Weights I

LeetCode Problem 3558 Difficulty: 🟡 Medium Topics: Math, Tree, Depth-First Search Solution LeetCode 3558 - Number of Ways to Assign Edge Weights I Problem Understanding We are given an undirected tree rooted at node 1 . Every edge initially has weight 0 , and we must assign each edge a weight of either 1 or 2 . The problem asks us to choose any node x that has the maximum...

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...

LeetCode 3539 - Find Sum of Array Product of Magical Sequences

LeetCode Problem 3539 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics, Bitmask Solution Problem Understanding This problem asks us to compute the sum of array products for all magical sequences of a given length. A magical sequence is defined as a sequence of indices into the input array nums of length m , such that when you sum 2 raised to each element of the sequence, the...

LeetCode 3556 - Sum of Largest Prime Substrings

LeetCode Problem 3556 Difficulty: 🟡 Medium Topics: Hash Table, Math, String, Sorting, Number Theory Solution Problem Understanding The problem requires identifying prime numbers from all possible substrings of a given string of digits and summing the three largest unique primes. In simpler terms, given a string s of length up to 10, we must consider every contiguous sequence of digits, convert it to an integer (ignoring any leading zeros), and...

LeetCode 3537 - Fill a Special Grid

LeetCode Problem 3537 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Matrix Solution Problem Understanding The problem asks us to construct a structured $2^n \times 2^n$ matrix filled with all integers from $0$ to $4^n - 1$, arranged in a very specific recursive ordering constraint across quadrants. A grid is considered special if it satisfies two key properties. First, there is a strict ordering between its four quadrants: every value...

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...

LeetCode 3531 - Count Covered Buildings

LeetCode Problem 3531 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting Solution Problem Understanding The task asks us to count how many buildings in a given set are covered in all four cardinal directions: left, right, above, and below, within an n x n grid. Each building is represented by a coordinate pair [x, y] , and all coordinates are unique. A building is considered covered if it satisfies two...

LeetCode 3528 - Unit Conversion I

LeetCode Problem 3528 Difficulty: 🟡 Medium Topics: Depth-First Search, Breadth-First Search, Graph Theory Solution Problem Understanding The problem is asking us to compute, for each unit type from 0 to n-1 , the number of that unit equivalent to a single unit of type 0 . We are given a list of direct conversion relationships between units. Each conversion specifies that 1 unit of sourceUnit is equivalent to some integer...

LeetCode 3521 - Find Product Recommendation Pairs

LeetCode Problem 3521 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding This problem asks us to identify product pairs that are frequently purchased by the same customers. The goal is to support a recommendation feature similar to "Customers who bought this also bought...", where products that commonly appear together in customer purchase histories can be suggested to future buyers. The ProductPurchases table contains one row for each (user_id, product_id) combination....

LeetCode 3519 - Count Numbers with Non-Decreasing Digits

LeetCode Problem 3519 Difficulty: 🔴 Hard Topics: Math, String, Dynamic Programming Solution LeetCode 3519 - Count Numbers with Non-Decreasing Digits Problem Understanding We are given two very large integers l and r as decimal strings and a base b where 2 ≤ b ≤ 10 . For every integer x in the inclusive range [l, r] , we consider its representation in base b . We want to count how...

LeetCode 3526 - Range XOR Queries with Subarray Reversals

LeetCode Problem 3526 Difficulty: 🔴 Hard Topics: Array, Tree, Binary Tree Solution Problem Understanding The problem asks us to maintain a dynamic array of integers under three types of operations: point updates, range XOR queries, and in-place subarray reversals. We are required to process a sequence of queries and return the results of only the XOR range queries in the order they appear. The input array nums represents an initial...

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...

LeetCode 3505 - Minimum Operations to Make Elements Within K Subarrays Equal

LeetCode Problem 3505 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Sliding Window, Heap (Priority Queue) Solution Problem Understanding You are given an integer array nums , and you want to create at least k non-overlapping subarrays. Every chosen subarray must have length exactly x , and after performing some modifications, every element inside each chosen subarray must become equal. The only allowed operation is increasing or decreasing...

LeetCode 3522 - Calculate Score After Performing Instructions

LeetCode Problem 3522 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Simulation Solution Problem Understanding The problem presents a simulated execution environment defined by two parallel arrays, instructions and values , each of length n . Each index i represents a single instruction. The instructions[i] element can either be "add" or "jump" . If the instruction is "add" , the associated values[i] is added to a running score , and...

LeetCode 3504 - Longest Palindrome After Substring Concatenation II

LeetCode Problem 3504 Difficulty: 🔴 Hard Topics: Two Pointers, String, Dynamic Programming Solution LeetCode 3504, Longest Palindrome After Substring Concatenation II Problem Understanding We are given two strings, s and t . We may choose any substring from s and any substring from t . Either substring is allowed to be empty. After selecting them, we concatenate them in this exact order: substring_from_s + substring_from_t The resulting string must be...

LeetCode 3520 - Minimum Threshold for Inversion Pairs Count

LeetCode Problem 3520 Difficulty: 🟡 Medium Topics: Array, Binary Search, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem asks us to find the minimum threshold x such that there are at least k inversion pairs in an array nums of integers. An inversion pair (i, j) is defined by three conditions: first, the indices satisfy i < j ; second, the values satisfy nums[i] > nums[j] ; and...

LeetCode 3482 - Analyze Organization Hierarchy

LeetCode Problem 3482 Difficulty: 🔴 Hard Topics: Database Solution LeetCode 3482 - Analyze Organization Hierarchy Problem Understanding This problem is a hierarchical organization analysis task over an employee table that forms a tree structure. Each employee has a unique employee_id , a name, a salary, and a manager_id . The employee whose manager_id is NULL is the CEO and serves as the root of the organization tree. Every other employee...

LeetCode 3468 - Find the Number of Copy Arrays

LeetCode Problem 3468 Difficulty: 🟡 Medium Topics: Array, Math Solution LeetCode 3468 - Find the Number of Copy Arrays Problem Understanding We are given an array original and a range constraint for every position in the form of bounds[i] = [ui, vi] . We need to count how many arrays copy satisfy two conditions. The first condition states that the difference between consecutive elements in copy must be exactly the...

LeetCode 3464 - Maximize the Distance Between Points on a Square

LeetCode Problem 3464 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Geometry, Sorting Solution LeetCode 3464 - Maximize the Distance Between Points on a Square Problem Understanding We are given a square of side length side . Every point in the input lies somewhere on the boundary of this square. We must choose exactly k points from the given set. For any two selected points, we can compute their Manhattan...

LeetCode 3453 - Separate Squares I

LeetCode Problem 3453 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution LeetCode 3453 - Separate Squares I Problem Understanding We are given a collection of axis-aligned squares. Each square is represented by three integers: xi : x-coordinate of the bottom-left corner yi : y-coordinate of the bottom-left corner li : side length The square therefore occupies the region: $$[x_i, x_i + l_i] \times [y_i, y_i + l_i]$$ We must find...

LeetCode 3445 - Maximum Difference Between Even and Odd Frequency II

LeetCode Problem 3445 Difficulty: 🔴 Hard Topics: String, Sliding Window, Enumeration, Prefix Sum Solution LeetCode 3445 - Maximum Difference Between Even and Odd Frequency II Problem Understanding We are given a string s consisting only of digits '0' through '4' , and an integer k . For any substring subs whose length is at least k , we may choose two characters: Character a must appear an odd number of...

LeetCode 3502 - Minimum Cost to Reach Every Position

LeetCode Problem 3502 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding We are given an array cost of length n . There are n + 1 positions in a line, numbered from 0 to n . Initially, we are standing at position n , which means we are at the very end of the line. To move forward in the line, we can swap positions with other people. The cost...

LeetCode 3419 - Minimize the Maximum Edge Weight of Graph

LeetCode Problem 3419 Difficulty: 🟡 Medium Topics: Binary Search, Depth-First Search, Breadth-First Search, Graph Theory, Shortest Path Solution Problem Understanding The problem is asking us to manipulate a directed weighted graph in order to minimize the maximum edge weight while satisfying two constraints: every node must be able to reach node 0, and no node may have more outgoing edges than a given threshold . The input consists of: n...

LeetCode 3414 - Maximum Score of Non-overlapping Intervals

LeetCode Problem 3414 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Sorting Solution Problem Understanding This problem combines weighted interval scheduling with an additional constraint: we may select at most 4 intervals, and if multiple selections achieve the same maximum total weight, we must return the lexicographically smallest list of original indices. Each interval is represented as: [left, right, weight] where: left is the starting position right is the...

LeetCode 3412 - Find Mirror Score of a String

LeetCode Problem 3412 Difficulty: 🟡 Medium Topics: Hash Table, String, Stack, Simulation Solution LeetCode 3412 - Find Mirror Score of a String Problem Understanding We are given a lowercase English string s . Every letter has a unique "mirror" letter obtained by reversing the alphabet. For example: 'a' ↔ 'z' 'b' ↔ 'y' 'c' ↔ 'x' and so on. We process the string from left to right. For each position...

LeetCode 3406 - Find the Lexicographically Largest String From the Box II

LeetCode Problem 3406 Difficulty: 🔴 Hard Topics: Two Pointers, String Solution LeetCode 3406 - Find the Lexicographically Largest String From the Box II Problem Understanding We are given a string word of length n and an integer numFriends . In every round, Alice splits the entire string into exactly numFriends non-empty pieces. Every possible valid split is considered exactly once. Every piece produced by every split is placed into a...

LeetCode 3401 - Find Circular Gift Exchange Chains

LeetCode Problem 3401 Difficulty: 🔴 Hard Topics: Database Solution Here’s a full technical solution guide following your requested format for LeetCode 3401 - Find Circular Gift Exchange Chains : Problem Understanding This problem asks us to analyze a table of gift exchanges in a Secret Santa setting and identify circular chains of gift exchanges. Each row in the SecretSanta table represents a gift transaction, with giver_id as the person giving...

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...

LeetCode 3495 - Minimum Operations to Make Array Elements Zero

LeetCode Problem 3495 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem presents a sequence of queries, each defining a contiguous array of integers nums from l to r inclusive. For each array, we are allowed to perform an operation repeatedly: select any two integers a and b and replace them with floor(a / 4) and floor(b / 4) . The goal is to determine the...

LeetCode 3770 - Largest Prime from Consecutive Prime Sum

LeetCode Problem 3770 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 3770 - Largest Prime from Consecutive Prime Sum Problem Understanding The problem gives us an integer n and asks us to find the largest prime number that satisfies two conditions: It is less than or equal to n . It can be written as the sum of one or more consecutive prime numbers starting from 2 ....

LeetCode 3768 - Minimum Inversion Count in Subarrays of Fixed Length

LeetCode Problem 3768 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Sliding Window Solution LeetCode 3768 - Minimum Inversion Count in Subarrays of Fixed Length Problem Understanding We are given an array nums of length n and an integer k . For every contiguous subarray of length k , we must compute its inversion count, then return the smallest inversion count among all such windows. An inversion is a pair of...

LeetCode 3764 - Most Common Course Pairs

LeetCode Problem 3764 Difficulty: 🔴 Hard Topics: — Solution Problem Understanding The course_completions table records every course completed by every user. Each row contains the user, the course they completed, the completion date, and the rating they gave that course. The problem asks us to identify common learning pathways among strong students. A student is considered a top performer only if they satisfy two conditions: They completed at least 5...

LeetCode 3762 - Minimum Operations to Equalize Subarrays

LeetCode Problem 3762 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Segment Tree Solution Problem Understanding We are given an array nums and a fixed integer k . A single operation allows us to choose any element and either increase it by exactly k or decrease it by exactly k . We may perform as many operations as needed. For each query [l, r] , we only consider the subarray...

LeetCode 3760 - Maximum Substrings With Distinct Start

LeetCode Problem 3760 Difficulty: 🟡 Medium Topics: Hash Table, String Solution LeetCode 3760 - Maximum Substrings With Distinct Start Problem Understanding The problem asks us to split a string into as many non-empty substrings as possible, with one important restriction: the first character of every substring must be different from the first character of every other substring. In other words, if we divide the string into several contiguous pieces, and...

LeetCode 3751 - Total Waviness of Numbers in Range I

LeetCode Problem 3751 Difficulty: 🟡 Medium Topics: Math, Dynamic Programming, Enumeration Solution LeetCode 3751 - Total Waviness of Numbers in Range I Problem Understanding This problem asks us to compute the total waviness of every integer in an inclusive range [num1, num2] . For a single number, waviness is defined as the number of digits that are either peaks or valleys. A digit is a peak if it is strictly...

LeetCode 3748 - Count Stable Subarrays

LeetCode Problem 3748 Difficulty: 🔴 Hard Topics: Array, Binary Search, Prefix Sum Solution Problem Understanding The problem asks us to count "stable" subarrays within a given array nums . A subarray is stable if it contains no inversions , which means that for any two indices i < j in the subarray, nums[i] <= nums[j] . Essentially, a stable subarray is non-decreasing . We are given multiple queries [li, ri]...

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...

LeetCode 3744 - Find Kth Character in Expanded String

LeetCode Problem 3744 Difficulty: 🟡 Medium Topics: String Solution LeetCode 3744 - Find Kth Character in Expanded String Problem Understanding The problem gives us a string s containing one or more lowercase words separated by single spaces. From this original string, we conceptually build a new string t using a special expansion rule. For each word, the first character appears once, the second character appears twice, the third character appears...

LeetCode 3743 - Maximize Cyclic Partition Score

LeetCode Problem 3743 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding We are given a cyclic array nums , which means the array is considered to wrap around from the last element back to the first element. We want to partition the entire cycle into at most k contiguous subarrays. Since the array is cyclic, one of the subarrays is allowed to cross the boundary between the last...

LeetCode 3734 - Lexicographically Smallest Palindromic Permutation Greater Than Target

LeetCode Problem 3734 Difficulty: 🔴 Hard Topics: Two Pointers, String, Enumeration Solution Problem Understanding We are given two strings, s and target , of the same length n . The goal is to rearrange the characters of s into a palindrome and then choose, among all possible palindromic permutations, the lexicographically smallest one that is strictly greater than target . A string a is lexicographically greater than a string b...

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...

LeetCode 3726 - Remove Zeros in Decimal Representation

LeetCode Problem 3726 Difficulty: 🟢 Easy Topics: Math, Simulation Solution LeetCode 3726 - Remove Zeros in Decimal Representation Problem Understanding The problem gives us a positive integer n and asks us to remove every digit '0' from its decimal representation. After all zero digits have been removed, we must return the resulting value as an integer. In other words, we first view the number as a sequence of decimal digits....

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 ....

LeetCode 3716 - Find Churn Risk Customers

LeetCode Problem 3716 Difficulty: 🟡 Medium Topics: — Solution Find Churn Risk Customers Problem Understanding This problem asks us to identify subscribers who appear likely to churn based on their subscription history. The data is stored in the subscription_events table, where each row represents a subscription-related action performed by a user. Each event records the subscription state after that action. A user may start a subscription, upgrade to a more...

LeetCode 3715 - Sum of Perfect Square Ancestors

LeetCode Problem 3715 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Tree, Depth-First Search, Counting, Number Theory Solution Problem Understanding This problem asks us to compute a sum across all non-root nodes in a tree based on ancestor relationships and the property of perfect squares. We are given a rooted tree of n nodes, represented as an edge list. Each node has a positive integer value from the nums array....

LeetCode 3707 - Equal Score Substrings

LeetCode Problem 3707 Difficulty: 🟢 Easy Topics: String, Prefix Sum Solution Problem Understanding The problem asks us to determine if a given string s can be split into two non-empty substrings such that the sum of the alphabetic positions of characters in the left substring is equal to the sum in the right substring. Each character 'a' to 'z' maps to values 1 through 26 respectively. The input is a...

LeetCode 3706 - Maximum Distance Between Unequal Words in Array II

LeetCode Problem 3706 Difficulty: 🟡 Medium Topics: Array, String Solution LeetCode 3706 - Maximum Distance Between Unequal Words in Array II Problem Understanding We are given an array of strings called words . Our goal is to find two different indices i and j such that the strings at those positions are different, meaning words[i] != words[j] . For every valid pair, the distance is defined as: $$j - i...

LeetCode 3705 - Find Golden Hour Customers

LeetCode Problem 3705 Difficulty: 🟡 Medium Topics: — Solution Problem Understanding This problem asks us to identify "golden hour customers" from a restaurant's order history. A golden hour customer is defined as someone who consistently orders during peak hours and maintains high satisfaction. Specifically, a customer must meet all of the following conditions: they must have made at least three orders, at least 60% of their orders must fall within...

LeetCode 3697 - Compute Decimal Representation

LeetCode Problem 3697 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding This problem asks us to decompose a positive integer n into the fewest possible base-10 components , where a base-10 component is defined as a single digit (1-9) multiplied by a power of 10. Essentially, we are breaking n down into its decimal place contributions . For example, for n = 537 , the hundreds place contributes 500,...

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...

LeetCode 3693 - Climbing Stairs II

LeetCode Problem 3693 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem is an extension of the classic "climbing stairs" dynamic programming problem but with more complex jump costs. You are given a staircase with n + 1 steps, numbered from 0 to n . Each intermediate step i (1-indexed) has an associated cost costs[i] . You start at step 0 with zero cost. From any step...

LeetCode 3694 - Distinct Points Reachable After Substring Removal

LeetCode Problem 3694 Difficulty: 🟡 Medium Topics: Hash Table, String, Sliding Window, Prefix Sum Solution LeetCode 3694 - Distinct Points Reachable After Substring Removal Problem Understanding We are given a movement string s consisting of the four directions: U increases the y-coordinate by 1. D decreases the y-coordinate by 1. L decreases the x-coordinate by 1. R increases the x-coordinate by 1. Starting from (0, 0) , the entire string...

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...

LeetCode 3686 - Number of Stable Subsequences

LeetCode Problem 3686 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to count how many subsequences of a given integer array are stable , where stability is defined by a constraint on parity patterns inside the subsequence itself. A subsequence is formed by deleting zero or more elements without changing the relative order of the remaining elements. A subsequence is considered unstable if, when...

LeetCode 3688 - Bitwise OR of Even Numbers in an Array

LeetCode Problem 3688 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Simulation Solution Problem Understanding This problem asks us to compute the bitwise OR of all even numbers in a given integer array nums . A number is considered even if it is divisible by 2, meaning its least significant bit is 0. The task is to iterate through the array, select only the even numbers, and combine them using the...

LeetCode 3683 - Earliest Time to Finish One Task

LeetCode Problem 3683 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3683 - Earliest Time to Finish One Task Problem Understanding The problem gives us a list of tasks, where each task is represented by two integers: si , the time when the task starts. ti , the amount of time required to complete the task. A task finishes at time: $$\text{finishTime} = s_i + t_i$$ Our goal is to determine...

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...

LeetCode 3677 - Count Binary Palindromic Numbers

LeetCode Problem 3677 Difficulty: 🔴 Hard Topics: Math, Bit Manipulation Solution Problem Understanding We are given a non-negative integer n and asked to count how many integers k in the range [0, n] have a binary representation that is a palindrome when written without leading zeros. A binary palindrome means that if you take the binary string of a number and read it from left to right or right to...

LeetCode 3682 - Minimum Index Sum of Common Elements

LeetCode Problem 3682 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding This problem is asking us to identify the smallest sum of indices from two equal-length arrays, nums1 and nums2 , such that the elements at those indices are equal. Formally, we want a pair (i, j) where nums1[i] == nums2[j] , and we want the minimum value of i + j . If no such pair exists,...

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...

LeetCode 3676 - Count Bowl Subarrays

LeetCode Problem 3676 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution Problem Understanding The problem asks us to count how many subarrays in an array of distinct integers satisfy a specific “bowl” condition. A subarray nums[l...r] is considered a bowl if it has length at least 3 and the smaller of its two endpoints is strictly greater than the maximum value of all elements strictly inside the subarray. In...

LeetCode 3674 - Minimum Operations to Equalize Array

LeetCode Problem 3674 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Brainteaser Solution Let's go step by step and produce a fully detailed, reference-style solution guide for LeetCode 3674 following your requested formatting. Problem Understanding The problem asks us to make all elements of an integer array nums equal using the minimum number of operations. Each operation consists of selecting a contiguous subarray and replacing every element in that subarray with...

LeetCode 3667 - Sort Array By Absolute Value

LeetCode Problem 3667 Difficulty: 🟢 Easy Topics: Array, Math, Two Pointers, Sorting Solution Problem Understanding The problem asks us to reorder an integer array such that the elements are sorted in non-decreasing order of their absolute values . This means we are not sorting based on the actual numeric value, but rather based on how far each number is from zero on the number line, regardless of sign. In simpler...

LeetCode 3668 - Restore Finishing Order

LeetCode Problem 3668 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3668 - Restore Finishing Order Problem Understanding This problem gives us two arrays: order , which represents the finishing order of all participants in a race. friends , which contains the IDs of our friends. The array order is a permutation of the integers from 1 to n , meaning every participant appears exactly once. The position of...

LeetCode 3665 - Twisted Mirror Path Count

LeetCode Problem 3665 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to count all unique paths from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) of a binary grid where certain cells contain mirrors. The robot can move only right or down , but mirrors change its trajectory in a very specific way: moving right into...

LeetCode 3664 - Two-Letter Card Game

LeetCode Problem 3664 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting, Enumeration Solution Problem Understanding Each card consists of exactly two lowercase letters. A card is only relevant if it contains the given letter x somewhere in its two positions. During the game, we repeatedly select two cards that satisfy two conditions: Both cards contain the letter x . The two strings differ in exactly one position. After selecting...

LeetCode 3662 - Filter Characters by Frequency

LeetCode Problem 3662 Difficulty: 🟢 Easy Topics: Hash Table, String, Counting Solution Problem Understanding This problem asks us to filter a string based on character frequency while preserving the original order of characters. We are given a string s consisting only of lowercase English letters and an integer k . The goal is to construct a new string by keeping only those characters whose total frequency in the entire string...

LeetCode 3663 - Find The Least Frequent Digit

LeetCode Problem 3663 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Counting Solution Problem Understanding The problem asks us to find the least frequent digit in the decimal representation of a given integer n . In other words, we need to count how many times each digit from 0 to 9 appears in the number, and then return the smallest digit that occurs the fewest times. The input is a...

LeetCode 3658 - GCD of Odd and Even Sums

LeetCode Problem 3658 Difficulty: 🟢 Easy Topics: Math, Number Theory Solution Problem Understanding The problem asks us to calculate the greatest common divisor (GCD) of two specific sums derived from an integer input n . The first sum, sumOdd , is the sum of the first n positive odd numbers, and the second sum, sumEven , is the sum of the first n positive even numbers. The input n is...

LeetCode 3657 - Find Loyal Customers

LeetCode Problem 3657 Difficulty: 🟡 Medium Topics: — Solution Problem Understanding This problem is a SQL aggregation and filtering task. We are given a table named customer_transactions that contains every transaction performed by customers. Each row represents either a purchase or a refund. A customer is considered loyal only if all three conditions are satisfied: They have made at least 3 purchase transactions. Their activity spans at least 30 days....

LeetCode 3651 - Minimum Cost Path with Teleportations

LeetCode Problem 3651 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem asks us to find the minimum cost to travel from the top-left corner (0, 0) of a 2D grid to the bottom-right corner (m - 1, n - 1) . Each cell contains a non-negative integer representing its cost. There are two ways to move: Normal move : move either right or down, paying...

LeetCode 3655 - XOR After Range Multiplication Queries II

LeetCode Problem 3655 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer Solution Problem Understanding We are given an array nums and a list of queries. Each query has the form: [li, ri, ki, vi] For a query, we start at index li and repeatedly jump forward by ki until we pass ri . Every visited position is multiplied by vi , and the result is taken modulo 10^9 + 7...

LeetCode 3653 - XOR After Range Multiplication Queries I

LeetCode Problem 3653 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Simulation Solution LeetCode 3653 - XOR After Range Multiplication Queries I Problem Understanding We are given an integer array nums and a list of queries. Each query has the form: [li, ri, ki, vi] For a query, we start at index li and repeatedly move forward by ki positions until we exceed ri . Every visited index is updated...

LeetCode 3652 - Best Time to Buy and Sell Stock using Strategy

LeetCode Problem 3652 Difficulty: 🟡 Medium Topics: Array, Sliding Window, Prefix Sum Solution Problem Understanding This problem asks us to calculate the maximum possible profit from a stock trading strategy with the option to modify it once in a very specific way. You are given two arrays: prices , which contains the stock price on each day, and strategy , which tells you what action to take each day: -1...

LeetCode 3647 - Maximum Weight in Two Bags

LeetCode Problem 3647 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem asks us to distribute a set of items, each with a given weight, into two separate bags with fixed capacity limits, in order to maximize the total weight placed across both bags. Each item in the input array weights can be used at most once, and for each item we must decide one of three...

LeetCode 3648 - Minimum Sensors to Cover Grid

LeetCode Problem 3648 Difficulty: 🟡 Medium Topics: Math Solution Problem Understanding The problem gives an n × m grid where each cell is identified by coordinates (r, c) . A sensor can be placed on any cell, and its coverage is defined using Chebyshev distance. Specifically, a sensor at (r, c) covers every cell (r2, c2) such that max(|r - r2|, |c - c2|) ≤ k . This means each...

LeetCode 3646 - Next Special Palindrome Number

LeetCode Problem 3646 Difficulty: 🔴 Hard Topics: Backtracking, Bit Manipulation Solution Problem Understanding This problem asks us to construct a number system under two simultaneous constraints and then perform a “next greater element” query over that constrained set. We are given an integer n , and we must find the smallest integer strictly greater than n such that the number satisfies a special structural property. A number is considered special...

LeetCode 3640 - Trionic Array II

LeetCode Problem 3640 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding We are given an integer array nums , and we must find the maximum possible sum of a contiguous subarray that follows a very specific shape: It first increases strictly. Then decreases strictly. Then increases strictly again. More formally, for a subarray nums[l...r] , there must exist indices: l < p < q < r such that:...

LeetCode 3643 - Flip Square Submatrix Vertically

LeetCode Problem 3643 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Matrix Solution LeetCode 3643 - Flip Square Submatrix Vertically Problem Understanding This problem gives us an m x n matrix called grid and three integers: x , y , and k . The values x and y specify the top-left corner of a square submatrix, while k specifies the side length of that square. Therefore, the submatrix occupies: Problem Understanding...

LeetCode 3641 - Longest Semi-Repeating Subarray

LeetCode Problem 3641 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 3641 - Longest Semi-Repeating Subarray Problem Understanding We are given an integer array nums and an integer k . A subarray is considered semi-repeating if the number of distinct values that appear more than once inside that subarray is at most k . To understand this carefully, consider a frequency map for a subarray: If a...

LeetCode 3636 - Threshold Majority Queries

LeetCode Problem 3636 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Divide and Conquer, Counting, Prefix Sum Solution Problem Understanding The problem asks us to process multiple queries on a given array nums where each query specifies a subarray defined by [li, ri] and a threshold . For each query, we need to find an element in the subarray that appears at least threshold times. If multiple elements meet...

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...

LeetCode 3632 - Subarrays with XOR at Least K

LeetCode Problem 3632 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Prefix Sum Solution Problem Understanding This problem asks us to count the number of contiguous subarrays of a given array nums such that the bitwise XOR of all elements in the subarray is greater than or equal to a given integer k . The input array nums consists of positive integers, and k is a non-negative integer. A contiguous...

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...

LeetCode 3625 - Count Number of Trapezoids II

LeetCode Problem 3625 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Geometry Solution Problem Understanding The problem asks us to count the number of unique trapezoids that can be formed from a set of points on a 2D Cartesian plane. Each point is given as a pair of integers representing its x and y coordinates. A trapezoid is defined as a convex quadrilateral with at least one pair of parallel...

LeetCode 3626 - Find Stores with Inventory Imbalance

LeetCode Problem 3626 Difficulty: 🟡 Medium Topics: — Solution Problem Understanding This problem asks us to identify stores with an inventory imbalance . Specifically, for each store, we need to compare the quantity of the most expensive product against the quantity of the cheapest product . A store is considered imbalanced if the most expensive product has fewer units in stock than the cheapest product. Additionally, we need to calculate...

LeetCode 3620 - Network Recovery Pathways

LeetCode Problem 3620 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Graph Theory, Topological Sort, Heap (Priority Queue), Shortest Path Solution LeetCode 3620 - Network Recovery Pathways Problem Understanding We are given a directed acyclic graph (DAG) with n nodes numbered from 0 to n - 1 . Each directed edge is represented as: u -> v with cost c and stored in: edges[i] = [u, v, c] We...

LeetCode 3617 - Find Students with Study Spiral Pattern

LeetCode Problem 3617 Difficulty: 🔴 Hard Topics: — Solution Problem Understanding The task asks us to identify students who exhibit a very specific behavioral pattern in their study history, called a Study Spiral Pattern. We are given two relational tables: one describing students and another describing their study sessions over time. Each study session includes the subject studied, the date, and the number of hours spent. The goal is to...

LeetCode 3622 - Check Divisibility by Digit Sum and Product

LeetCode Problem 3622 Difficulty: 🟢 Easy Topics: Math Solution Problem Understanding The problem asks us to determine if a given positive integer n is divisible by the sum of two specific quantities derived from its digits: the digit sum and the digit product . The digit sum is obtained by adding all the digits of n , and the digit product is obtained by multiplying all the digits of n...

LeetCode 3612 - Process String with Special Operations I

LeetCode Problem 3612 Difficulty: 🟡 Medium Topics: String, Simulation Solution Problem Understanding The problem asks us to simulate the construction of a string called result by processing an input string s from left to right. The input string contains lowercase English letters and three special operators: * , # , and % . Each character in the input modifies the evolving result string in a specific way. A lowercase letter...

LeetCode 3619 - Count Islands With Total Value Divisible by K

LeetCode Problem 3619 Difficulty: 🟡 Medium Topics: Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix Solution Problem Understanding The problem is asking us to count islands in a 2D grid where the sum of the values in each island is divisible by a given integer k . An island is defined as a group of positive integers that are 4-directionally connected, meaning we can move horizontally or vertically between adjacent positive...

LeetCode 3618 - Split Array by Prime Indices

LeetCode Problem 3618 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 3618 - Split Array by Prime Indices Problem Understanding The problem gives us an integer array nums and asks us to divide its elements into two groups based on their indices. Array A contains all elements whose indices are prime numbers. Array B contains all remaining elements, meaning indices that are not prime. Remember that array indices...

LeetCode 3614 - Process String with Special Operations II

LeetCode Problem 3614 Difficulty: 🔴 Hard Topics: String, Simulation Solution Problem Understanding The problem defines a transformation process over a string s that contains lowercase letters and three special operation characters: '*' , '#' , and '%' . We process the string from left to right, maintaining a dynamically changing result string. Each lowercase letter is appended to the result. The '*' operation deletes the last character of the result...

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...

LeetCode 3606 - Coupon Code Validator

LeetCode Problem 3606 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Sorting Solution Problem Understanding The problem is asking us to validate a set of coupons based on three criteria: the coupon code must be a non-empty string containing only alphanumeric characters or underscores, the business line must belong to a set of four predefined categories, and the coupon must be active. We are given three arrays of equal length,...

LeetCode 3604 - Minimum Time to Reach Destination in Directed Graph

LeetCode Problem 3604 Difficulty: 🟡 Medium Topics: Graph Theory, Heap (Priority Queue), Shortest Path Solution Problem Understanding This problem asks us to compute the minimum time required to reach the last node in a directed graph where each edge has a time window constraint. You start at node 0 at time 0 , and each edge [u, v, start, end] can only be used if you traverse it at an...

LeetCode 3607 - Power Grid Maintenance

LeetCode Problem 3607 Difficulty: 🟡 Medium Topics: Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem gives an undirected graph of c power stations labeled from 1 to c , connected by bidirectional cables. These connections define connected components, which are referred to as power grids. Importantly, these grids are static, meaning connectivity does not change even if stations...

LeetCode 3599 - Partition Array to Minimize XOR

LeetCode Problem 3599 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Prefix Sum Solution Problem Understanding This problem asks us to partition an array of integers, nums , into exactly k non-empty contiguous subarrays, and then compute the bitwise XOR of each subarray. The goal is to minimize the maximum XOR among these subarrays. Essentially, we are trying to distribute the elements into k groups such that the "largest...

LeetCode 3594 - Minimum Time to Transport All Individuals

LeetCode Problem 3594 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Graph Theory, Heap (Priority Queue), Shortest Path, Bitmask Solution Problem Understanding This problem is a shortest-path optimization over a highly constrained state space where you are repeatedly moving groups of people across a river using a single boat. The twist is that the travel time is not fixed: it depends both on the slowest person in the group and on...

LeetCode 3597 - Partition String

LeetCode Problem 3597 Difficulty: 🟡 Medium Topics: Hash Table, String, Trie, Simulation Solution LeetCode 3597 - Partition String Problem Understanding We are given a string s and must partition it into segments according to a very specific process. We start at the current position in the string and begin building a segment character by character. As we extend the segment, we continuously check whether that exact segment has already appeared...

LeetCode 3415 - Find Products with Three Consecutive Digits

LeetCode Problem 3415 Difficulty: 🟢 Easy Topics: Database Solution Problem Understanding This is a SQL database problem involving pattern matching on strings. We are given a table named Products with two columns: Column Description product_id Unique identifier for each product name Product name string The goal is to return all products whose names contain a sequence of exactly three consecutive digits . The important detail is the word exactly ....

LeetCode 3596 - Minimum Cost Path with Alternating Directions I

LeetCode Problem 3596 Difficulty: 🟡 Medium Topics: Math, Brainteaser Solution Problem Understanding This problem requires computing the minimum total cost to traverse a grid from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) while following a strict alternating movement pattern. Each cell (i, j) has a cost to enter, calculated as (i + 1) * (j + 1) . Movement is constrained by...

LeetCode 3592 - Inverse Coin Change

LeetCode Problem 3592 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem gives us a 1-indexed array numWays , where numWays[i] indicates the number of ways to form a total amount i using an infinite supply of some unknown coin denominations . The goal is to recover the original set of coin denominations. The array effectively represents the output of a classical coin change problem, but in...

LeetCode 3591 - Check if Any Element Has Prime Frequency

LeetCode Problem 3591 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Counting, Number Theory Solution Problem Understanding This problem asks us to determine whether any number in an array appears a prime number of times. In other words, for each unique number in the input array nums , we calculate its frequency-the number of occurrences-and check if that frequency is a prime number. If at least one element has a...

LeetCode 3589 - Count Prime-Gap Balanced Subarrays

LeetCode Problem 3589 Difficulty: 🟡 Medium Topics: Array, Math, Queue, Sliding Window, Number Theory, Monotonic Queue Solution Count Prime-Gap Balanced Subarrays Problem Understanding We are given an integer array nums and an integer k . We must count how many contiguous subarrays satisfy two conditions: The subarray contains at least two prime numbers. Among all prime numbers inside that subarray, the difference between the largest prime and the smallest prime...

LeetCode 3586 - Find COVID Recovery Patients

LeetCode Problem 3586 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding The task is to identify patients who have recovered from COVID based on their testing history. We are given two tables: one containing patient demographic information and another containing COVID test records with timestamps and results. A patient is considered recovered if they have at least one positive test and, after that positive test, they later have at least...

LeetCode 3585 - Find Weighted Median Node in Tree

LeetCode Problem 3585 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted tree with n nodes. A tree is an undirected connected graph with exactly n - 1 edges, which guarantees that there is exactly one simple path between any two nodes. Each edge has a positive weight. For every query [u, v] , we look at...

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...

LeetCode 3582 - Generate Tag for Video Caption

LeetCode Problem 3582 Difficulty: 🟢 Easy Topics: String, Simulation Solution Problem Understanding The problem asks us to transform a given caption string into a valid video tag following a strict sequence of rules. The input is a single string caption consisting only of English letters and spaces. These words must be transformed into a single hashtag-style identifier. The transformation has three ordered steps. First, we must merge all words into...

LeetCode 3580 - Find Consistently Improving Employees

LeetCode Problem 3580 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding The task asks us to identify employees whose performance has consistently improved over their most recent three performance reviews. Each employee may have multiple reviews stored in the performance_reviews table, and we must focus only on the last three reviews per employee when ordered by review_date . For each employee, we first determine whether they have at least three...

LeetCode 3579 - Minimum Steps to Convert String with Operations

LeetCode Problem 3579 Difficulty: 🔴 Hard Topics: String, Dynamic Programming Solution Problem Understanding The problem asks us to transform one string, word1 , into another string, word2 , using the minimum number of operations. Both strings have equal length and consist only of lowercase English letters. The allowed operations are applied on contiguous substrings of word1 and include replacing a character, swapping two characters, or reversing the entire substring. Each...

LeetCode 3578 - Count Partitions With Max-Min Difference at Most K

LeetCode Problem 3578 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Queue, Sliding Window, Prefix Sum, Monotonic Queue Solution LeetCode 3578 - Count Partitions With Max-Min Difference at Most K Problem Understanding We are given an array nums and an integer k . We want to split the array into one or more contiguous, non-empty segments. Every element must belong to exactly one segment, and the segments must preserve the original...

LeetCode 3577 - Count the Number of Computer Unlocking Permutations

LeetCode Problem 3577 Difficulty: 🟡 Medium Topics: Array, Math, Brainteaser, Combinatorics Solution Problem Understanding The problem presents a set of n computers, each with a unique password complexity represented in an array complexity of length n . The computers are labeled 0 to n - 1 , and only computer 0 is initially unlocked. To unlock another computer i , you must already have unlocked at least one computer j...

LeetCode 3573 - Best Time to Buy and Sell Stock V

LeetCode Problem 3573 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 3573 - Best Time to Buy and Sell Stock V Problem Understanding This problem extends the classic stock trading dynamic programming family by allowing two different kinds of transactions. A normal transaction consists of buying first and selling later. If the stock price rises, the profit is: $$\text{sell price} - \text{buy price}$$ A short selling transaction reverses the...

LeetCode 3574 - Maximize Subarray GCD Score

LeetCode Problem 3574 Difficulty: 🔴 Hard Topics: Array, Math, Enumeration, Number Theory Solution Problem Understanding The problem asks us to choose a contiguous subarray from an array of positive integers after performing at most k doubling operations, where each element can be doubled at most once. After applying these optional doublings, we compute the score of a subarray as the product of its length and the greatest common divisor (GCD)...

LeetCode 3571 - Find the Shortest Superstring II

LeetCode Problem 3571 Difficulty: 🟢 Easy Topics: String Solution Problem Understanding This problem asks us to construct the shortest string that contains two given strings, s1 and s2 , as substrings. In other words, we are asked to merge s1 and s2 in such a way that no unnecessary characters are added, but both strings appear contiguously somewhere in the resulting string. The inputs, s1 and s2 , are both...

LeetCode 3570 - Find Books with No Available Copies

LeetCode Problem 3570 Difficulty: 🟢 Easy Topics: Database Solution Problem Understanding This problem asks us to identify books in a library system that are both fully unavailable for borrowing and currently have active borrowers who have not returned them yet. We are given two tables. The library_books table contains static information about each book, including how many total physical copies exist in the library. The borrowing_records table captures individual borrow...

LeetCode 3567 - Minimum Absolute Difference in Sliding Submatrix

LeetCode Problem 3567 Difficulty: 🟡 Medium Topics: Array, Sorting, Matrix Solution Problem Understanding The problem requires computing a specific statistic for every contiguous k x k submatrix of a given m x n integer matrix grid . For each submatrix, we must find the minimum absolute difference between any two distinct elements. The final result is a 2D array ans of size (m - k + 1) x (n -...

LeetCode 3560 - Find Minimum Log Transportation Cost

LeetCode Problem 3560 Difficulty: 🟢 Easy Topics: Math Solution Problem Understanding The problem asks us to transport two logs of lengths n and m using three trucks, where each truck can carry a log of length at most k . If a log is longer than k , it must be cut into smaller pieces. Cutting a log of length x into two pieces of lengths len1 and len2 incurs...

LeetCode 3565 - Sequential Grid Path Cover

LeetCode Problem 3565 Difficulty: 🟡 Medium Topics: Array, Recursion, Matrix Solution Problem Understanding The problem asks us to find a path that visits every cell of a given m x n grid exactly once while visiting certain numbered cells in a specified order. Specifically, the grid contains integers from 1 to k in exactly one cell each, and the rest of the cells are zeros. The path can start at...

LeetCode 3563 - Lexicographically Smallest String After Adjacent Removals

LeetCode Problem 3563 Difficulty: 🔴 Hard Topics: String, Dynamic Programming Solution Problem Understanding The problem asks us to find the lexicographically smallest string that can be formed by repeatedly removing adjacent pairs of characters in a string s that are consecutive in the alphabet. Consecutive letters can be in either order (e.g., 'a' followed by 'b' or 'b' followed by 'a' ) and the alphabet is considered circular, meaning 'a'...

LeetCode 3561 - Resulting String After Adjacent Removals

LeetCode Problem 3561 Difficulty: 🟡 Medium Topics: String, Stack, Simulation Solution Problem Understanding The problem asks us to repeatedly remove pairs of adjacent characters in a string that are consecutive in the alphabet, considering the alphabet as circular. "Consecutive in the alphabet" means two characters where the difference in their positions in the alphabet is 1, either forwards or backwards, and 'a' and 'z' are also considered consecutive. The operation...

LeetCode 3559 - Number of Ways to Assign Edge Weights II

LeetCode Problem 3559 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given an undirected tree with n nodes, rooted at node 1 . Every edge will eventually receive a weight of either 1 or 2 . For each query [u, v] , we only care about the unique path connecting u and v . All edges outside that path are...

LeetCode 3549 - Multiply Two Polynomials

LeetCode Problem 3549 Difficulty: 🔴 Hard Topics: Array, Math Solution Problem Understanding The input arrays represent polynomials in coefficient form. If: poly1 = [a0, a1, a2, ...] then it represents: A(x) = a0 + a1x + a2x² + ... Similarly: poly2 = [b0, b1, b2, ...] represents: B(x) = b0 + b1x + b2x² + ... The task is to compute the product polynomial: R(x) = A(x) × B(x) and...

LeetCode 3554 - Find Category Recommendation Pairs

LeetCode Problem 3554 Difficulty: 🔴 Hard Topics: Database Solution Problem Understanding This is a SQL database problem involving customer purchasing behavior across product categories. We are given two tables: ProductPurchases records which products each user purchased. A user may purchase multiple products, and each purchase has a quantity. The quantity is irrelevant for this problem because we only care whether a user bought from a category, not how much they...

LeetCode 3553 - Minimum Weighted Subgraph With the Required Paths II

LeetCode Problem 3553 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted, undirected tree with n nodes. Because the graph is a tree, there is exactly one simple path between any two nodes. For each query [src1, src2, dest] , we must find the minimum total weight of a connected subtree such that both src1 and src2 can reach...

LeetCode 3552 - Grid Teleportation Traversal

LeetCode Problem 3552 Difficulty: 🟡 Medium Topics: Array, Hash Table, Breadth-First Search, Matrix Solution Problem Understanding This problem presents a 2D grid traversal scenario with obstacles and teleportation portals. You are given a matrix of characters representing cells. Empty cells '.' are freely passable, '#' represents obstacles that block movement, and uppercase letters 'A' - 'Z' are teleportation portals. The task is to move from the top-left (0, 0) to...

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...

LeetCode 3546 - Equal Sum Grid Partition I

LeetCode Problem 3546 Difficulty: 🟡 Medium Topics: Array, Matrix, Enumeration, Prefix Sum Solution LeetCode 3546 - Equal Sum Grid Partition I Problem Understanding This problem asks us to determine whether a rectangular grid of positive integers can be split into two parts with exactly the same sum using a single straight cut. The cut can be made in only one of two ways: A horizontal cut between two adjacent rows....

LeetCode 3544 - Subtree Inversion Sum

LeetCode Problem 3544 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding This problem asks us to select a subset of nodes in a rooted tree such that each selected node triggers a subtree inversion, and inversions interact through ancestor-descendant relationships with a distance constraint. Each inversion multiplies all values in the corresponding subtree by −1, and multiple inversions stack multiplicatively, meaning each node’s final sign...

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...

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...

LeetCode 3543 - Maximum Weighted K-Edge Path

LeetCode Problem 3543 Difficulty: 🟡 Medium Topics: Hash Table, Dynamic Programming, Graph Theory Solution LeetCode 3543 - Maximum Weighted K-Edge Path Problem Understanding We are given a directed acyclic graph (DAG) with n nodes and weighted directed edges. Each edge is represented as [u, v, w] , meaning there is a directed edge from node u to node v with weight w . The goal is to find a path...

LeetCode 3540 - Minimum Time to Visit All Houses

LeetCode Problem 3540 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution LeetCode 3540 - Minimum Time to Visit All Houses Problem Understanding This problem describes a set of n houses arranged in a circle. Between adjacent houses, there are two directed road systems: forward[i] is the distance from house i to (i + 1) % n . backward[i] is the distance from house i to (i - 1 + n)...

LeetCode 3541 - Find Most Frequent Vowel and Consonant

LeetCode Problem 3541 Difficulty: 🟢 Easy Topics: Hash Table, String, Counting Solution Problem Understanding The problem requires analyzing a string s composed of lowercase English letters and determining the sum of the maximum frequency of vowels and the maximum frequency of consonants. Vowels are defined as 'a' , 'e' , 'i' , 'o' , and 'u' . All other letters are consonants. The frequency of a character is the number...

LeetCode 3538 - Merge Operations for Minimum Travel Time

LeetCode Problem 3538 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding This problem presents a road of length l kilometers, segmented by n signs at strictly increasing positions, where the first sign is at the start of the road ( position[0] = 0 ) and the last sign is at the end of the road ( position[n-1] = l ). Each segment between consecutive signs has...

LeetCode 3535 - Unit Conversion II

LeetCode Problem 3535 Difficulty: 🟡 Medium Topics: Array, Math, Depth-First Search, Breadth-First Search, Graph Theory Solution Problem Understanding The input describes a collection of unit conversion relationships. Each conversion is given as: source -> target with factor f meaning: 1 unit of source = f units of target The important observation is that there are exactly n - 1 conversion edges among n units, and the statement guarantees that unit...

LeetCode 3536 - Maximum Product of Two Digits

LeetCode Problem 3536 Difficulty: 🟢 Easy Topics: Math, Sorting Solution LeetCode 3536 - Maximum Product of Two Digits Problem Understanding The problem gives us a positive integer n and asks us to find the maximum product that can be formed by multiplying any two digits that appear in the number. The input is a single integer. We must examine all of its digits and determine which pair of digits produces...

LeetCode 3533 - Concatenated Divisibility

LeetCode Problem 3533 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution LeetCode 3533 - Concatenated Divisibility Problem Understanding We are given an array nums containing up to 13 positive integers and an integer k . We may reorder the numbers in any permutation. After choosing an ordering, we concatenate the decimal representations of the numbers to form a single large integer. The task is to find a...

LeetCode 3529 - Count Cells in Overlapping Horizontal and Vertical Substrings

LeetCode Problem 3529 Difficulty: 🟡 Medium Topics: Array, String, Rolling Hash, String Matching, Matrix, Hash Function Solution Problem Understanding We are given a character matrix and a pattern string. The key observation is that the problem defines two unusual traversal orders: A horizontal traversal reads the matrix row by row, from left to right. When a row ends, reading continues at the beginning of the next row. A vertical traversal...

LeetCode 3532 - Path Existence Queries in a Graph I

LeetCode Problem 3532 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Union-Find, Graph Theory Solution Path Existence Queries in a Graph I Problem Understanding This problem defines an undirected graph implicitly through a sorted array nums . Each index in nums represents a graph node. Two nodes i and j are connected by an edge whenever: $$|nums[i] - nums[j]| \le maxDiff$$ We are then given many connectivity queries. For...

LeetCode 3530 - Maximum Profit from Valid Topological Order in DAG

LeetCode Problem 3530 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Graph Theory, Topological Sort, Bitmask Solution Problem Understanding The problem requires computing the maximum possible profit achievable by processing nodes of a Directed Acyclic Graph (DAG) in a valid topological order . Each node has a score, and the profit contribution of a node is its score multiplied by its position in the processing order (1-based). The goal...

LeetCode 3527 - Find the Most Common Response

LeetCode Problem 3527 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting Solution LeetCode 3527 - Find the Most Common Response Problem Understanding This problem gives us a two dimensional array of strings called responses . Each responses[i] represents all survey responses collected on the i th day. A response is simply a string such as "good" , "ok" , or "bad" . The important detail is that duplicate responses...

LeetCode 3525 - Find X Value of Array II

LeetCode Problem 3525 Difficulty: 🔴 Hard Topics: Array, Math, Segment Tree Solution Problem Understanding For each query, two things happen in order. First, we permanently update one element of nums : nums[index] = value This modification remains in effect for all future queries. Second, we conceptually remove the prefix nums[0..start-1] . After this removal, we are left with the suffix: nums[start..n-1] Now we must count how many ways we can...

LeetCode 3524 - Find X Value of Array I

LeetCode Problem 3524 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming Solution LeetCode 3524 - Find X Value of Array I Problem Understanding The operation described in the problem may initially look unusual, but it is actually equivalent to choosing a non-empty contiguous subarray. When we remove a prefix and a suffix that do not overlap, the elements left behind form a contiguous segment of the original array. Conversely, every...

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...

LeetCode 3518 - Smallest Palindromic Rearrangement II

LeetCode Problem 3518 Difficulty: 🔴 Hard Topics: Hash Table, Math, String, Combinatorics, Counting Solution Problem Understanding We are given a string s that is guaranteed to already be a palindrome. We may rearrange its characters, but the final rearranged string must also be a palindrome. Among all distinct palindromic permutations that can be formed from the characters of s , we must return the k -th lexicographically smallest one. If...

LeetCode 3515 - Shortest Path in a Weighted Tree

LeetCode Problem 3515 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Binary Indexed Tree, Segment Tree Solution LeetCode 3515. Shortest Path in a Weighted Tree Problem Understanding We are given a weighted tree with n nodes, rooted at node 1 . A tree has exactly one simple path between any pair of nodes. Since the tree is rooted at node 1 , every node has a unique path from the...

LeetCode 3514 - Number of Unique XOR Triplets II

LeetCode Problem 3514 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation, Enumeration Solution LeetCode 3514 - Number of Unique XOR Triplets II Problem Understanding We are given an integer array nums , and we must consider every triplet of indices (i, j, k) such that i <= j <= k . For each valid triplet, we compute: $$nums[i] \oplus nums[j] \oplus nums[k]$$ where ⊕ denotes the bitwise XOR operation. The...

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....

LeetCode 3513 - Number of Unique XOR Triplets I

LeetCode Problem 3513 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem asks us to determine the number of unique values that can result from taking the XOR of three elements in a given array nums , where the triplets (i, j, k) must satisfy i <= j <= k . Importantly, nums is a permutation of integers from 1 to n , meaning every integer...

LeetCode 3517 - Smallest Palindromic Rearrangement I

LeetCode Problem 3517 Difficulty: 🟡 Medium Topics: String, Sorting, Counting Sort Solution Problem Understanding The problem asks us to take a palindromic string s and return its lexicographically smallest palindromic permutation . In other words, we need to rearrange the characters of s into a palindrome that is the smallest possible if you were to compare it alphabetically with all other palindromic arrangements. The input string s is guaranteed to...

LeetCode 3516 - Find Closest Person

LeetCode Problem 3516 Difficulty: 🟢 Easy Topics: Math Solution LeetCode 3516 - Find Closest Person Problem Understanding This problem gives us three integers, x , y , and z , representing the positions of three people on a one-dimensional number line. Person 1 starts at position x , Person 2 starts at position y , and Person 3 remains stationary at position z . Both Person 1 and Person 2...

LeetCode 3512 - Minimum Operations to Make Array Sum Divisible by K

LeetCode Problem 3512 Difficulty: 🟢 Easy Topics: Array, Math Solution LeetCode 3512 - Minimum Operations to Make Array Sum Divisible by K Problem Understanding The problem gives us an integer array nums and an integer k . We are allowed to repeatedly perform one operation: choose any index i and decrease nums[i] by exactly 1 . Our goal is to determine the minimum number of such operations needed so that...

LeetCode 3510 - Minimum Pair Removal to Sort Array II

LeetCode Problem 3510 Difficulty: 🔴 Hard Topics: Array, Hash Table, Linked List, Heap (Priority Queue), Simulation, Doubly-Linked List, Ordered Set Solution LeetCode 3510: Minimum Pair Removal to Sort Array II Problem Understanding We are given an array nums . The operation is highly constrained: Among all adjacent pairs, find the pair with the minimum sum. If multiple adjacent pairs have the same minimum sum, choose the leftmost one. Replace those...

LeetCode 3509 - Maximum Product of Subsequences With an Alternating Sum Equal to K

LeetCode Problem 3509 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming Solution Problem Understanding The problem asks us to find a subsequence of a given integer array nums such that the alternating sum of the subsequence equals a target integer k , while maximizing the product of the numbers in that subsequence without exceeding a given limit . The alternating sum is defined as the sum of elements at...

LeetCode 3508 - Implement Router

LeetCode Problem 3508 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Design, Queue, Ordered Set Solution Problem Understanding The problem is asking us to design a Router data structure to manage network packets efficiently under memory constraints. Each packet has three attributes: source , destination , and timestamp . The router has a memory limit , meaning it can store only a fixed number of packets. If a new...

LeetCode 3507 - Minimum Pair Removal to Sort Array I

LeetCode Problem 3507 Difficulty: 🟢 Easy Topics: Array, Hash Table, Linked List, Heap (Priority Queue), Simulation, Doubly-Linked List, Ordered Set Solution LeetCode 3507 - Minimum Pair Removal to Sort Array I Problem Understanding We are given an array nums . At any step, we are not free to choose any adjacent pair. Instead, the operation is completely determined by the current state of the array: Find the adjacent pair whose...

LeetCode 3503 - Longest Palindrome After Substring Concatenation I

LeetCode Problem 3503 Difficulty: 🟡 Medium Topics: Two Pointers, String, Dynamic Programming, Enumeration Solution LeetCode 3503 - Longest Palindrome After Substring Concatenation I Problem Understanding We are given two strings, s and t , and we are allowed to choose: Any substring of s , including the empty string. Any substring of t , including the empty string. The chosen substring from s must come first, and the chosen substring...

LeetCode 3497 - Analyze Subscription Conversion

LeetCode Problem 3497 Difficulty: 🟡 Medium Topics: Database Solution Problem Understanding This is a SQL aggregation problem where we need to analyze user subscription behavior and return statistics only for users who successfully converted from a free trial to a paid subscription. The UserActivity table contains one row per user, per day, per activity type. The activity_type column can be one of three values: This is a SQL database problem...

LeetCode 3493 - Properties Graph

LeetCode Problem 3493 Difficulty: 🟡 Medium Topics: Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory Solution Problem Understanding The problem asks us to model a 2D array of integers, called properties , as an undirected graph. Each row of the array corresponds to a node in the graph. Two nodes are connected if the number of distinct integers they share is at least k . Our goal is...

LeetCode 3499 - Maximize Active Section with Trade I

LeetCode Problem 3499 Difficulty: 🟡 Medium Topics: String, Enumeration Solution Problem Understanding The problem gives a binary string s representing sections of a system, where '1' indicates an active section and '0' indicates an inactive section. We are allowed at most one trade to maximize the number of active sections. A trade consists of two operations applied sequentially on the string: Convert a contiguous block of '1' s surrounded by...

LeetCode 3501 - Maximize Active Section with Trade II

LeetCode Problem 3501 Difficulty: 🔴 Hard Topics: Array, String, Binary Search, Segment Tree Solution Problem Understanding The problem presents a binary string s where each character represents an active ( '1' ) or inactive ( '0' ) section. For each query, which specifies a substring of s , we are asked to determine the maximum number of active sections after performing at most one trade operation. A trade consists of...

LeetCode 3500 - Minimum Cost to Divide Array Into Subarrays

LeetCode Problem 3500 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding This problem asks us to partition an array nums into contiguous subarrays, where each subarray contributes a weighted cost to the total. The cost for a subarray nums[l..r] depends on two components: the sum of the elements in the subarray, adjusted by a factor k multiplied by the order of the subarray, and the sum...

LeetCode 3498 - Reverse Degree of a String

LeetCode Problem 3498 Difficulty: 🟢 Easy Topics: String, Simulation Solution LeetCode 3498 - Reverse Degree of a String Problem Understanding The problem asks us to compute a special value called the reverse degree of a string. Normally, letters are assigned positions in the alphabet as: 'a' = 1 'b' = 2 ... 'z' = 26 However, this problem uses the reversed alphabet order , where: 'a' = 26 'b' =...

LeetCode 3492 - Maximum Containers on a Ship

LeetCode Problem 3492 Difficulty: 🟢 Easy Topics: Math Solution Problem Understanding This problem describes a cargo ship with an n × n deck. Since each cell on the deck can hold exactly one container, the deck has a total capacity of: $$n^2$$ physical container positions. Every container has the same weight, w . The ship also has a maximum total weight limit, maxWeight . Even if the deck has enough...

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...

LeetCode 3494 - Find the Minimum Amount of Time to Brew Potions

LeetCode Problem 3494 Difficulty: 🟡 Medium Topics: Array, Simulation, Prefix Sum Solution Problem Understanding The problem asks us to simulate a sequential brewing process for potions performed by a series of wizards. Each wizard has a skill level that determines the speed at which they brew a potion, while each potion has a mana requirement that affects how long it takes to brew. Specifically, the time for wizard i to...

LeetCode 3491 - Phone Number Prefix

LeetCode Problem 3491 Difficulty: 🟢 Easy Topics: Array, String, Trie, Sorting Solution Problem Understanding The problem is asking us to determine whether any phone number in a given list is a prefix of another phone number. In simpler terms, if you have a list of strings representing numbers, you need to check that no string starts with another string from the list. If all numbers are independent prefixes, the output...

LeetCode 3490 - Count Beautiful Numbers

LeetCode Problem 3490 Difficulty: 🔴 Hard Topics: Dynamic Programming Solution Problem Understanding This problem asks us to count the number of positive integers between l and r (inclusive) that are beautiful . A number is defined as beautiful if the product of its digits is divisible by the sum of its digits. In simpler terms, for a number n , if sum_digits(n) divides product_digits(n) evenly, then n is beautiful. The...

LeetCode 3489 - Zero Array Transformation IV

LeetCode Problem 3489 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine the minimum number of sequential queries needed to transform an integer array nums into a Zero Array, where every element is zero. Each query specifies a subarray [li, ri] and a value vali , and the query allows us to decrement any subset of indices in that subarray by exactly vali...

LeetCode 3488 - Closest Equal Element Queries

LeetCode Problem 3488 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search Solution Problem Understanding The problem asks us to process a series of queries on a circular array nums . Each query specifies an index, and for that index, we need to find the minimum circular distance to any other index with the same value. The circular distance means that after the last element, the array wraps back to...

LeetCode 3486 - Longest Special Path II

LeetCode Problem 3486 Difficulty: 🔴 Hard Topics: Array, Hash Table, Tree, Depth-First Search, Prefix Sum Solution LeetCode 3486 - Longest Special Path II Problem Understanding We are given a rooted tree with n nodes. The tree is rooted at node 0 , and every edge has a positive length. Each node also contains a value stored in the array nums . A path is considered special if it satisfies two...

LeetCode 3480 - Maximize Subarrays After Removing One Conflicting Pair

LeetCode Problem 3480 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Enumeration, Prefix Sum Solution Here’s a detailed technical solution guide following your requested format for LeetCode 3480 - Maximize Subarrays After Removing One Conflicting Pair . Problem Understanding The problem gives you an integer n , which defines a sorted array nums = [1, 2, ..., n] . You are also given a list of conflictingPairs , each representing two...

LeetCode 3484 - Design Spreadsheet

LeetCode Problem 3484 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design, Matrix Solution LeetCode 3484 - Design Spreadsheet Problem Understanding This problem asks us to design a very small spreadsheet system that supports three operations on cells and one operation for evaluating simple formulas. The spreadsheet always contains exactly 26 columns, labeled 'A' through 'Z' , and a configurable number of rows. Each cell can store an integer value....

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...

LeetCode 3481 - Apply Substitutions

LeetCode Problem 3481 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort Solution LeetCode 3481 - Apply Substitutions Problem Understanding This problem gives us a collection of replacement rules and a text containing placeholders. Every placeholder has the format %X% , where X is a single uppercase letter corresponding to one of the replacement keys. The important detail is that replacement values may...

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...

LeetCode 3479 - Fruits Into Baskets III

LeetCode Problem 3479 Difficulty: 🟡 Medium Topics: Array, Binary Search, Segment Tree, Ordered Set Solution LeetCode 3479: Fruits Into Baskets III Problem Understanding This problem gives us two arrays of equal length: fruits[i] represents the quantity of the i-th fruit type. baskets[j] represents the capacity of the j-th basket. We process the fruit types from left to right. For each fruit quantity, we must place it into the leftmost available...

LeetCode 3478 - Choose K Elements With Maximum Sum

LeetCode Problem 3478 Difficulty: 🟡 Medium Topics: Array, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem asks us to compute a "maximum sum" for each index in an array based on a relationship with other elements. Specifically, for each index i in nums1 , we must consider all previous or other indices j where nums1[j] < nums1[i] , and then select up to k values from nums2[j] to maximize...

LeetCode 3477 - Fruits Into Baskets II

LeetCode Problem 3477 Difficulty: 🟢 Easy Topics: Array, Binary Search, Segment Tree, Simulation, Ordered Set Solution Problem Understanding This problem asks us to simulate the placement of fruits into baskets following very specific rules. We are given two arrays of equal length, fruits and baskets . Each element in fruits represents the quantity of a fruit type, and each element in baskets represents the capacity of a basket. We need...

LeetCode 3475 - DNA Pattern Recognition

LeetCode Problem 3475 Difficulty: 🟡 Medium Topics: Database Solution LeetCode 3475 - DNA Pattern Recognition Problem Understanding This problem provides a database table named Samples that contains DNA sequences and their associated species. Each row represents a single biological sample, identified by a unique sample_id . The task is to examine every DNA sequence and determine whether it matches four different biological patterns. For each sample, we must generate four...

LeetCode 3471 - Find the Largest Almost Missing Integer

LeetCode Problem 3471 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3471 - Find the Largest Almost Missing Integer Problem Understanding The problem gives us an integer array nums and an integer k . We consider every contiguous subarray of length k . An integer is called almost missing if it appears in exactly one of those size- k subarrays. Our goal is to find the largest integer that...

LeetCode 3461 - Check If Digits Are Equal in String After Operations I

LeetCode Problem 3461 Difficulty: 🟢 Easy Topics: Math, String, Simulation, Combinatorics, Number Theory Solution Problem Understanding This problem asks us to repeatedly transform a string of digits by summing consecutive pairs modulo 10, until only two digits remain, and then check whether those two digits are equal. In other words, we start with a string s of length at least 3 and, at each step, generate a new string where...

LeetCode 3472 - Longest Palindromic Subsequence After at Most K Operations

LeetCode Problem 3472 Difficulty: 🟡 Medium Topics: String, Dynamic Programming Solution Here’s a complete, detailed technical solution guide for LeetCode 3472 following your formatting rules. Problem Understanding The problem asks us to find the length of the longest palindromic subsequence in a string s after performing at most k operations . Each operation allows us to increment or decrement a character by one in the alphabet, with wraparound from 'a'...

LeetCode 3470 - Permutations IV

LeetCode Problem 3470 Difficulty: 🔴 Hard Topics: Array, Math, Combinatorics, Enumeration Solution LeetCode 3470 - Permutations IV Problem Understanding We are given two integers, n and k . We must consider all permutations of the numbers 1 through n that satisfy an alternating parity condition. In a valid permutation, every pair of adjacent elements must have different parity. In other words: Odd must be followed by even. Even must be...

LeetCode 3469 - Find Minimum Cost to Remove Array Elements

LeetCode Problem 3469 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem is asking for the minimum total cost required to remove all elements from an integer array nums under a very specific set of operations. At each step, we can either remove any two elements from the first three elements of the array, and the cost for that operation is the maximum of the two elements...

LeetCode 3467 - Transform Array by Parity

LeetCode Problem 3467 Difficulty: 🟢 Easy Topics: Array, Sorting, Counting Solution LeetCode 3467 - Transform Array by Parity Problem Understanding The problem gives us an integer array nums and asks us to transform it using three operations that must be performed in a specific order. First, every even number must be replaced with 0 . Second, every odd number must be replaced with 1 . After this transformation, the array...

LeetCode 3459 - Length of Longest V-Shaped Diagonal Segment

LeetCode Problem 3459 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Memoization, Matrix Solution Problem Understanding We are given an n x m matrix whose entries are only 0 , 1 , or 2 . A valid V-shaped diagonal segment must satisfy two independent requirements: First, the values along the path must follow a very specific sequence. The first cell must contain 1 . Every subsequent cell must alternate between 2...

LeetCode 3465 - Find Products with Valid Serial Numbers

LeetCode Problem 3465 Difficulty: 🟢 Easy Topics: Database Solution Problem Understanding The problem asks us to query a database table called products to identify rows where the description column contains a valid serial number. A valid serial number is defined as a substring that begins with "SN", followed by exactly four digits, a hyphen, and then exactly four more digits. For example, SN1234-5678 is valid, but SN123-4567 or SN12345-6789 are...

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...

LeetCode 3463 - Check If Digits Are Equal in String After Operations II

LeetCode Problem 3463 Difficulty: 🔴 Hard Topics: Math, String, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to repeatedly transform a string of digits until only two digits remain, and then check if those two digits are the same. The transformation involves taking each consecutive pair of digits, summing them, and taking the result modulo 10 to form a new digit. This process is applied repeatedly, replacing the...

LeetCode 3460 - Longest Common Prefix After at Most One Removal

LeetCode Problem 3460 Difficulty: 🟡 Medium Topics: Two Pointers, String Solution LeetCode 3460 - Longest Common Prefix After at Most One Removal Problem Understanding We are given two lowercase strings, s and t . We may remove at most one character from s . The removal is optional, so we are also allowed to leave s unchanged. After performing zero or one removal, we want to compute the length of...

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...

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...

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...

LeetCode 3456 - Find Special Substring of Length K

LeetCode Problem 3456 Difficulty: 🟢 Easy Topics: String Solution LeetCode 3456 - Find Special Substring of Length K Problem Understanding The problem gives us a string s and an integer k . We need to determine whether there exists a substring of length exactly k that satisfies three conditions. First, every character inside the substring must be identical. In other words, the substring must consist of only one distinct character...

LeetCode 3454 - Separate Squares II

LeetCode Problem 3454 Difficulty: 🔴 Hard Topics: Array, Binary Search, Segment Tree, Sweep Line Solution LeetCode 3454 - Separate Squares II Problem Understanding This problem asks us to find the smallest horizontal line y = H that divides the union area of a collection of axis-aligned squares into two equal halves. Each square is represented as: (xi, yi) = bottom-left corner li = side length Therefore, a square covers: x-range:...

LeetCode 3450 - Maximum Students on a Single Bench

LeetCode Problem 3450 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem provides a list of student-seat assignments, where each entry has the form [student_id, bench_id] . Each pair indicates that a particular student is sitting on a particular bench. The goal is to determine which bench has the largest number of unique students sitting on it and return that count. The important detail is that a...

LeetCode 3452 - Sum of Good Numbers

LeetCode Problem 3452 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3452 - Sum of Good Numbers Problem Understanding This problem gives us an integer array nums and an integer k . For every position i , we need to determine whether nums[i] is a good number. A number is considered good if it is strictly greater than the element located k positions to its left, nums[i - k] , when...

LeetCode 3451 - Find Invalid IP Addresses

LeetCode Problem 3451 Difficulty: 🔴 Hard Topics: Database Solution Problem Understanding This is a SQL database problem where we must identify all invalid IPv4 addresses that appear in the logs table and count how many times each invalid address occurs. The input table contains one row per server access log. Each row includes a unique log_id , an IP address stored as a string in the ip column, and an...

LeetCode 3448 - Count Substrings Divisible By Last Digit

LeetCode Problem 3448 Difficulty: 🔴 Hard Topics: String, Dynamic Programming Solution LeetCode 3448 - Count Substrings Divisible By Last Digit Problem Understanding We are given a string s consisting only of decimal digits. Every substring of s represents a non-negative integer, and leading zeros are allowed. For each substring, we look at its last digit. If the last digit is non-zero, we check whether the numeric value of the substring...

LeetCode 3446 - Sort Matrix by Diagonals

LeetCode Problem 3446 Difficulty: 🟡 Medium Topics: Array, Sorting, Matrix Solution Problem Understanding We are given an n x n square matrix grid . Every cell belongs to exactly one top-left to bottom-right diagonal. Two cells (r1, c1) and (r2, c2) are on the same diagonal if r1 - c1 == r2 - c2 . The problem asks us to independently sort each diagonal, but the required sorting order depends...

LeetCode 3442 - Maximum Difference Between Even and Odd Frequency I

LeetCode Problem 3442 Difficulty: 🟢 Easy Topics: Hash Table, String, Counting Solution Problem Understanding This problem requires analyzing the frequency of characters in a given string and computing a specific difference. You are given a string s consisting only of lowercase English letters. For each character in the string, you can count how many times it appears. Some characters will appear an odd number of times , and some will...

LeetCode 3447 - Assign Elements to Groups with Constraints

LeetCode Problem 3447 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem requires assigning elements from one array, elements , to groups defined by another array, groups , under a divisibility constraint. Specifically, for each group groups[i] , we must find the smallest index j in elements such that groups[i] % elements[j] == 0 . If no such element exists, we assign -1 for that group. Multiple...

LeetCode 3444 - Minimum Increments for Target Multiples in an Array

LeetCode Problem 3444 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Number Theory, Bitmask Solution LeetCode 3444 - Minimum Increments for Target Multiples in an Array Problem Understanding We are given two arrays: nums , the array whose elements we are allowed to increase. target , a small array containing values that must each be represented by at least one multiple somewhere in the final version of nums...

LeetCode 3441 - Minimum Cost Good Caption

LeetCode Problem 3441 Difficulty: 🔴 Hard Topics: String, Dynamic Programming Solution Problem Understanding We are given a lowercase string caption . We may repeatedly change any character one step forward or backward in the alphabet. Because we can apply this operation multiple times, converting a character x into a character y costs exactly: $$|x - y|$$ where the difference is measured by alphabet position. The goal is to transform the...

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:...

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...

LeetCode 3437 - Permutations III

LeetCode Problem 3437 Difficulty: 🟡 Medium Topics: Array, Backtracking Solution LeetCode 3437 - Permutations III Problem Understanding We are given a single integer n , and we need to generate all permutations of the numbers from 1 to n . However, not every permutation is valid. A permutation is considered an alternating permutation if every pair of adjacent elements has different parity. In other words: An odd number must always...

LeetCode 3436 - Find Valid Emails

LeetCode Problem 3436 Difficulty: 🟢 Easy Topics: Database Solution Problem Understanding The problem requires us to identify valid email addresses from a Users table in a database. Each row contains a user_id and an email string. The definition of a valid email is very specific: it must contain exactly one @ symbol , end with .com , have a local part (before the @ ) composed solely of alphanumeric characters...

LeetCode 3435 - Frequencies of Shortest Supersequences

LeetCode Problem 3435 Difficulty: 🔴 Hard Topics: Array, String, Bit Manipulation, Graph Theory, Topological Sort, Enumeration Solution Problem Understanding The problem asks us to find all shortest common supersequences (SCS) of a given list of two-character strings words . A shortest common supersequence is a string of minimum length that contains each word in words as a subsequence. Importantly, the output should not include SCSs that are permutations of each...

LeetCode 3433 - Count Mentions Per User

LeetCode Problem 3433 Difficulty: 🟡 Medium Topics: Array, Math, Sorting, Simulation Solution LeetCode 3433 - Count Mentions Per User Problem Understanding This problem asks us to simulate a sequence of user activity events and count how many times each user is mentioned across all message events. We are given: numberOfUsers , the total number of users with IDs from 0 to numberOfUsers - 1 events , where each event is...

LeetCode 3428 - Maximum and Minimum Sums of at Most Size K Subsequences

LeetCode Problem 3428 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Sorting, Combinatorics Solution Problem Understanding We are given an array nums and an integer k . For every subsequence whose size is at most k , we look at two values: The minimum element in that subsequence. The maximum element in that subsequence. We add minimum + maximum for every valid subsequence, then return the total modulo 10^9 +...

LeetCode 3429 - Paint House IV

LeetCode Problem 3429 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem is asking us to paint n houses arranged in a line with three available colors for each house, minimizing the total painting cost while satisfying two constraints. The first constraint is the standard one from the classic "Paint House" problem: no two adjacent houses can have the same color. The second constraint is new and...

LeetCode 3427 - Sum of Variable Length Subarrays