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Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

Practice › LeetCode › LeetCode 36xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

Practice › LeetCode › LeetCode 34xx ›

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...

Practice › LeetCode › LeetCode 34xx ›

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...

Practice › LeetCode › LeetCode 34xx ›

LeetCode 3408 - Design Task Manager

LeetCode Problem 3408 Difficulty: 🟡 Medium Topics: Hash Table, Design, Heap (Priority Queue), Ordered Set Solution LeetCode 3408. Design Task Manager Problem Understanding This problem asks us to design a data structure that maintains a collection of tasks belonging to different users. Each task has three pieces of information: userId , the user who owns the task taskId , a unique identifier for the task priority , which determines execution...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1847 - Closest Room

LeetCode Problem 1847 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sorting, Ordered Set Solution LeetCode 1847: Closest Room Problem Understanding We are given a list of hotel rooms, where each room has: Problem Understanding The problem gives us a collection of hotel rooms, where each room has two attributes: A unique room ID A room size We are also given several queries. Each query contains: preferred : the room ID...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2612 - Minimum Reverse Operations

LeetCode Problem 2612 Difficulty: 🔴 Hard Topics: Array, Hash Table, Breadth-First Search, Union-Find, Ordered Set Solution This will be a very large, multi-thousand-word technical guide because of the required depth, full proofs, worked examples, Python and Go implementations, detailed walkthroughs, complexity reasoning, and exhaustive tests. To ensure quality and avoid truncation, I will split it cleanly into sections across messages. Part 1: Problem Understanding, Approaches, Algorithm Walkthrough, and Python Solution...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3244 - Shortest Distance After Road Addition Queries II

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

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2363 - Merge Similar Items

LeetCode Problem 2363 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting, Ordered Set Solution Problem Understanding The problem gives us two collections of items, items1 and items2 , where every item is represented as a pair: [value, weight] The value acts like a unique identifier for an item, while weight represents that item's associated weight. Within each individual array, values are guaranteed to be unique, meaning no value appears twice...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2613 - Beautiful Pairs

LeetCode Problem 2613 Difficulty: 🔴 Hard Topics: Array, Math, Divide and Conquer, Geometry, Sorting, Ordered Set Solution Problem Understanding The problem asks us to find a beautiful pair of indices (i, j) in two integer arrays nums1 and nums2 of equal length. A pair (i, j) is beautiful if it minimizes the sum of the absolute differences between the corresponding elements: |nums1[i] - nums1[j]| + |nums2[i] - nums2[j]| among all...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2762 - Continuous Subarrays

LeetCode Problem 2762 Difficulty: 🟡 Medium Topics: Array, Queue, Sliding Window, Heap (Priority Queue), Ordered Set, Monotonic Queue Solution That is a long, structured technical guide. To make sure I target the correct problem and avoid wasting your time, can you confirm the exact LeetCode problem title for 2762 ? I believe it is “Continuous Subarrays” , but I want to ensure I generate the full guide for the right...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1912 - Design Movie Rental System

LeetCode Problem 1912 Difficulty: 🔴 Hard Topics: Array, Hash Table, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem requires designing a movie rental system for multiple shops, where each shop carries at most one copy of each movie. We are asked to implement a class that efficiently supports searching for available movies, renting them, returning them, and reporting the cheapest currently rented movies. The input consists of...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2336 - Smallest Number in Infinite Set

LeetCode Problem 2336 Difficulty: 🟡 Medium Topics: Hash Table, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to implement a data structure representing an infinite set of positive integers, initially containing all integers starting from 1. We need to provide two main operations: popSmallest , which removes and returns the smallest integer in the set, and addBack , which adds a previously removed integer back...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2424 - Longest Uploaded Prefix

LeetCode Problem 2424 Difficulty: 🟡 Medium Topics: Hash Table, Binary Search, Union-Find, Design, Binary Indexed Tree, Segment Tree, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to design a data structure that tracks uploaded videos and continuously reports the length of the longest uploaded prefix. A prefix of uploaded videos means that every video from 1 through i has already been uploaded. The goal is to...

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3391 - Design a 3D Binary Matrix with Efficient Layer Tracking

LeetCode Problem 3391 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Heap (Priority Queue), Matrix, Ordered Set Solution Problem Understanding The problem asks us to design a data structure that manages a 3D binary matrix of size n x n x n . Every cell initially contains 0 , and we must support three operations efficiently: setCell(x, y, z) sets a specific cell to 1 . unsetCell(x, y, z) sets...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2426 - Number of Pairs Satisfying Inequality

LeetCode Problem 2426 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution LeetCode 2426 - Number of Pairs Satisfying Inequality Problem Understanding We are given two integer arrays, nums1 and nums2 , of the same length n , along with an integer diff . We must count how many index pairs (i, j) satisfy both: i < j nums1[i]...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2179 - Count Good Triplets in an Array

LeetCode Problem 2179 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding In this problem, we are given two arrays, nums1 and nums2 , each containing every integer from 0 to n - 1 exactly once. In other words, both arrays are permutations of the same set of values. We need to count how many triplets (x,...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2349 - Design a Number Container System

LeetCode Problem 2349 Difficulty: 🟡 Medium Topics: Hash Table, Design, Heap (Priority Queue), Ordered Set Solution LeetCode 2349 - Design a Number Container System Problem Understanding The problem asks us to design a data structure that supports two operations efficiently: Assign a number to a given index. Find the smallest index currently assigned to a given number. The important detail is that the change(index, number) operation can both insert and...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2817 - Minimum Absolute Difference Between Elements With Constraint

LeetCode Problem 2817 Difficulty: 🟡 Medium Topics: Array, Binary Search, Ordered Set Solution LeetCode 2817 - Minimum Absolute Difference Between Elements With Constraint Problem Understanding We are given an integer array nums and an integer x . We need to find two elements whose indices are separated by at least x , and among all such valid pairs, return the minimum possible absolute difference between their values. More formally, we...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2102 - Sequentially Ordinal Rank Tracker

LeetCode Problem 2102 Difficulty: 🔴 Hard Topics: Design, Heap (Priority Queue), Data Stream, Ordered Set Solution Problem Understanding The problem asks us to design a data structure that continuously tracks scenic locations ranked by two rules: A higher score means a better location. If two locations have the same score, the lexicographically smaller name is considered better. The system supports two operations: add(name, score) inserts a new location. get() returns...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3245 - Alternating Groups III

LeetCode Problem 3245 Difficulty: 🔴 Hard Topics: Array, Binary Indexed Tree, Ordered Set Solution Problem Understanding We are given a circular array called colors , where each element is either 0 or 1 . These represent red and blue tiles arranged in a ring, which means index 0 and index n - 1 are adjacent. A group is considered alternating if every adjacent pair inside that contiguous segment has different...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1902 - Depth of BST Given Insertion Order

LeetCode Problem 1902 Difficulty: 🟡 Medium Topics: Array, Tree, Binary Search Tree, Binary Tree, Ordered Set Solution Problem Understanding The problem gives us an array order that represents the exact sequence in which values are inserted into a binary search tree, usually abbreviated as BST. The array is a permutation of integers from 1 to n , which means every value appears exactly once and there are no duplicates. We...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3109 - Find the Index of Permutation

LeetCode Problem 3109 Difficulty: 🟡 Medium Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding The problem gives us a permutation perm of the integers [1, 2, ..., n] . A permutation is simply an arrangement of all numbers from 1 to n where each number appears exactly once. We are asked to determine the lexicographic index of this permutation...

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3092 - Most Frequent IDs

LeetCode Problem 3092 Difficulty: 🟡 Medium Topics: Array, Hash Table, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to maintain a collection of IDs that is updated incrementally based on two arrays, nums and freq . Each index i represents a step. At step i , we either add freq[i] copies of nums[i] to the collection if freq[i] is positive, or remove -freq[i] copies of nums[i]...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2382 - Maximum Segment Sum After Removals

LeetCode Problem 2382 Difficulty: 🔴 Hard Topics: Array, Union-Find, Prefix Sum, Ordered Set Solution Problem Understanding The problem gives us two arrays, nums and removeQueries , both of length n . The nums array contains positive integers. Initially, all elements are present, forming one contiguous segment. Then, elements are removed one by one according to the order defined in removeQueries . After each removal, the array becomes split into one...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2251 - Number of Flowers in Full Bloom

LeetCode Problem 2251 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Sorting, Prefix Sum, Ordered Set Solution Problem Understanding The problem asks us to determine, for a list of people arriving at certain times, how many flowers are in full bloom at the time of their arrival. Each flower has a start and end time representing the period it is in full bloom, inclusive of both endpoints. The input...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2213 - Longest Substring of One Repeating Character

LeetCode Problem 2213 Difficulty: 🔴 Hard Topics: Array, String, Segment Tree, Ordered Set Solution Problem Understanding The problem gives us an initial string s and a sequence of update operations. Each update changes exactly one character in the string. After every update, we must determine the length of the longest contiguous substring that contains only one repeating character. A substring is contiguous, so characters must appear next to each other....

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3073 - Maximum Increasing Triplet Value

LeetCode Problem 3073 Difficulty: 🟡 Medium Topics: Array, Ordered Set Solution Problem Understanding We are given an integer array nums , and we must find three indices (i, j, k) such that: i < j < k nums[i] < nums[j] < nums[k] Among all valid increasing triplets, we want to maximize the expression: $$nums[i] - nums[j] + nums[k]$$ The task is not to maximize the sum of the triplet. Instead,...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2713 - Maximum Strictly Increasing Cells in a Matrix

LeetCode Problem 2713 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Dynamic Programming, Memoization, Sorting, Matrix, Ordered Set Solution Problem Understanding The problem gives us an m x n matrix where each cell contains an integer value. We may start from any cell, and from the current cell we are allowed to move only within the same row or the same column. However, there is an important restriction: we...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2659 - Make Array Empty

LeetCode Problem 2659 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Binary Indexed Tree, Segment Tree, Sorting, Ordered Set Solution LeetCode 2659 - Make Array Empty Problem Understanding The problem gives us an array of distinct integers and defines two possible operations: If the first element is currently the smallest value in the array, we remove it. Otherwise, we move the first element to the end of the array. We...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2519 - Count the Number of K-Big Indices

LeetCode Problem 2519 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution LeetCode 2519 - Count the Number of K-Big Indices Problem Understanding This problem asks us to determine how many indices in an array satisfy a very specific condition related to smaller values on both sides. For an index i to be considered k-big , two separate requirements...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2158 - Amount of New Area Painted Each Day

LeetCode Problem 2158 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Ordered Set Solution Problem Understanding This problem describes a painting scenario represented as a one-dimensional number line. Each element in the input array paint[i] = [starti, endi] represents the section that needs to be painted on the i th day. The goal is to calculate, for each day, how much new area is painted-i.e., the part of the segment that...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2353 - Design a Food Rating System

LeetCode Problem 2353 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem is asking us to implement a food rating system that supports dynamic updates to the ratings of individual food items and allows querying for the highest-rated food for a given cuisine. Each food has a unique name, belongs to exactly one cuisine, and has an associated rating. The...

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3369 - Design an Array Statistics Tracker

LeetCode Problem 3369 Difficulty: 🔴 Hard Topics: Hash Table, Binary Search, Design, Queue, Heap (Priority Queue), Data Stream, Ordered Set Solution Problem Understanding The problem asks us to design a data structure that supports a stream of operations on a dynamic collection of integers. Numbers are added over time, and the oldest inserted number can also be removed. At any point, we must efficiently answer three statistical queries: The floored...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2276 - Count Integers in Intervals

LeetCode Problem 2276 Difficulty: 🔴 Hard Topics: Design, Segment Tree, Ordered Set Solution Problem Understanding This problem asks us to design a data structure that dynamically maintains a collection of integer intervals and efficiently reports how many distinct integers are covered by at least one interval. Initially, the interval set is empty. We must support two operations: add(left, right) , which inserts a new interval [left, right] count() , which...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3102 - Minimize Manhattan Distances

LeetCode Problem 3102 Difficulty: 🔴 Hard Topics: Array, Math, Geometry, Sorting, Ordered Set Solution Problem Understanding The problem asks us to minimize the maximum Manhattan distance between any two points on a 2D plane after removing exactly one point from the input list. The input points is an array of integer coordinates [[x1, y1], [x2, y2], ..., [xn, yn]] . The Manhattan distance between two points (x1, y1) and (x2,...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 715 - Range Module

LeetCode Problem 715 Difficulty: 🔴 Hard Topics: Design, Segment Tree, Ordered Set Solution Problem Understanding This problem asks us to design a data structure that dynamically tracks intervals on the number line. The tracked intervals are represented as half-open intervals, meaning [left, right) includes every value x such that left <= x < right . The data structure must support three operations: addRange(left, right) marks every value in [left, right)...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1818 - Minimum Absolute Sum Difference

LeetCode Problem 1818 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sorting, Ordered Set Solution Problem Understanding The problem gives two arrays of positive integers, nums1 and nums2 , both of equal length n . The goal is to calculate the absolute sum difference between these arrays, which is the sum of the absolute differences at each index: |nums1[i] - nums2[i]| . You are allowed to replace at most one element...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 493 - Reverse Pairs

LeetCode Problem 493 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding The problem asks us to count how many pairs of indices (i, j) satisfy two conditions: i < j nums[i] > 2 * nums[j] These pairs are called reverse pairs. Unlike the classic inversion count problem, where we check whether nums[i] > nums[j] , this...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 699 - Falling Squares

LeetCode Problem 699 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Ordered Set Solution Problem Understanding The problem describes a simulation of squares falling onto the X-axis. Each square is represented by two values: lefti , the X-coordinate of the square's left edge sideLengthi , the side length of the square A square occupies the interval: $$[lefti,\ lefti + sideLengthi)$$ When a square falls, it continues downward until one of two...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 327 - Count of Range Sum

LeetCode Problem 327 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution LeetCode 327 - Count of Range Sum Problem Understanding This problem asks us to count how many subarrays have sums that fall within a given inclusive range [lower, upper] . A range sum S(i, j) represents the sum of all elements from index i through index j...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 975 - Odd Even Jump

LeetCode Problem 975 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Sorting, Monotonic Stack, Ordered Set Solution Problem Understanding The problem asks us to determine how many starting indices in an array allow reaching the last element by performing a series of jumps defined as either odd-numbered or even-numbered. The distinction between odd and even jumps is crucial: odd-numbered jumps must move to the smallest value greater than or equal...

Practice › LeetCode › LeetCode 13xx ›

LeetCode 1348 - Tweet Counts Per Frequency

LeetCode Problem 1348 Difficulty: 🟡 Medium Topics: Hash Table, String, Binary Search, Design, Sorting, Ordered Set Solution Problem Understanding The problem is asking us to design a system that tracks tweets by their timestamp and allows querying the number of tweets in specific time intervals, split according to a frequency (minute, hour, or day). Specifically, we need to implement a TweetCounts class with two operations: recording a tweet and retrieving...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 497 - Random Point in Non-overlapping Rectangles

LeetCode Problem 497 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Reservoir Sampling, Prefix Sum, Ordered Set, Randomized Solution Problem Understanding The problem asks us to randomly pick an integer point from a set of non-overlapping rectangles in 2D space. Each rectangle is defined by its bottom-left (ai, bi) and top-right (xi, yi) corners. The goal is to ensure that every integer point inside the union of all rectangles has...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 218 - The Skyline Problem

LeetCode Problem 218 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Binary Indexed Tree, Segment Tree, Sweep Line, Sorting, Heap (Priority Queue), Ordered Set Solution Problem Understanding The Skyline Problem asks us to compute the visible outer contour formed by a collection of rectangular buildings when viewed from far away. Each building is represented by three integers: a left x-coordinate, a right x-coordinate, and a height. The buildings sit on...

Practice › LeetCode › LeetCode 08xx ›

LeetCode 895 - Maximum Frequency Stack

LeetCode Problem 895 Difficulty: 🔴 Hard Topics: Hash Table, Stack, Design, Ordered Set Solution Problem Understanding The problem is asking us to design a custom stack-like data structure that supports two operations: pushing values onto the stack and popping the most frequent element. A key difference from a traditional stack is that the pop operation does not necessarily remove the element at the top; instead, it removes the element with...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2034 - Stock Price Fluctuation

LeetCode Problem 2034 Difficulty: 🟡 Medium Topics: Hash Table, Design, Heap (Priority Queue), Data Stream, Ordered Set Solution Here’s a complete, detailed technical solution guide for LeetCode 2034 - Stock Price Fluctuation following your formatting and content requirements. Problem Understanding The problem presents a stream of stock price records where each record consists of a timestamp and a price . However, the stream is not guaranteed to be chronological, and...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1606 - Find Servers That Handled Most Number of Requests

LeetCode Problem 1606 Difficulty: 🔴 Hard Topics: Array, Heap (Priority Queue), Simulation, Ordered Set Solution Problem Understanding The problem presents a simulation scenario involving k servers, each uniquely identified from 0 to k-1 . Every server can handle only one request at a time , and requests arrive at discrete times given by the strictly increasing arrival array. Each request requires a certain load of time to complete. Requests are...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 363 - Max Sum of Rectangle No Larger Than K

LeetCode Problem 363 Difficulty: 🔴 Hard Topics: Array, Binary Search, Matrix, Prefix Sum, Ordered Set Solution Problem Understanding The problem asks us to find the rectangular submatrix whose sum is as large as possible while still being less than or equal to a given integer k . A rectangle in a matrix is any contiguous block of cells formed by choosing a range of rows and a range of columns....

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1675 - Minimize Deviation in Array

LeetCode Problem 1675 Difficulty: 🔴 Hard Topics: Array, Greedy, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to minimize the deviation in an array of positive integers. The deviation is defined as the difference between the maximum and minimum elements in the array. We can modify the array using two operations: if an element is even, we can divide it by 2, and if an element...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2021 - Brightest Position on Street

LeetCode Problem 2021 Difficulty: 🟡 Medium Topics: Array, Sorting, Prefix Sum, Ordered Set Solution Problem Understanding The problem asks us to find the position on a straight street that is illuminated by the largest number of street lamps, which is referred to as its brightness . The street is represented as a number line, and each street lamp is given as a pair [positioni, rangei] , which defines the interval...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1649 - Create Sorted Array through Instructions

LeetCode Problem 1649 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding The problem asks us to simulate building a sorted array incrementally. We process the instructions array from left to right, and for each value, we insert it into a container called nums while maintaining sorted order. However, the actual insertion is not the difficult part....

Practice › LeetCode › LeetCode 08xx ›

LeetCode 850 - Rectangle Area II

LeetCode Problem 850 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Sweep Line, Ordered Set Solution Problem Understanding This problem asks us to compute the total area covered by a set of axis-aligned rectangles on a 2D plane. Each rectangle is defined by its bottom-left and top-right coordinates [xi1, yi1, xi2, yi2] . The challenge is that rectangles can overlap, and any overlapping region must only be counted once . The...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 731 - My Calendar II

LeetCode Problem 731 Difficulty: 🟡 Medium Topics: Array, Binary Search, Design, Segment Tree, Prefix Sum, Ordered Set Solution Problem Understanding The problem asks us to design a calendar system that supports booking time intervals while enforcing one important rule: no point in time may be covered by three events simultaneously. Each event is represented as a half open interval [startTime, endTime) . This means the event includes startTime but excludes...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 732 - My Calendar III

LeetCode Problem 732 Difficulty: 🔴 Hard Topics: Binary Search, Design, Segment Tree, Prefix Sum, Ordered Set Solution Problem Understanding This problem asks us to design a calendar system that supports adding time intervals and reporting the highest number of overlapping events seen so far. Each booking is represented as a half open interval [startTime, endTime) . This means the event includes startTime but excludes endTime . Two events overlap only...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 635 - Design Log Storage System

LeetCode Problem 635 Difficulty: 🟡 Medium Topics: Hash Table, String, Design, Ordered Set Solution Problem Understanding The problem is asking us to design a log storage system that supports two primary operations: storing logs with unique IDs and timestamps, and retrieving logs based on a timestamp range and granularity. Each timestamp is represented as a string in the format YYYY:MM:DD:HH:MM:SS , which is zero-padded and guarantees lexicographic ordering aligns with...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 716 - Max Stack

LeetCode Problem 716 Difficulty: 🔴 Hard Topics: Linked List, Stack, Design, Doubly-Linked List, Ordered Set Solution Problem Understanding The problem asks us to design a stack data structure, MaxStack , which behaves like a normal stack with additional operations for efficiently accessing and removing the maximum element. Specifically, in addition to the standard stack operations push , pop , and top , we need to implement peekMax , which returns...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 729 - My Calendar I

LeetCode Problem 729 Difficulty: 🟡 Medium Topics: Array, Binary Search, Design, Segment Tree, Ordered Set Solution Problem Understanding The problem asks us to design a calendar system that supports booking events without allowing overlapping intervals. Each event is represented as a half-open interval [startTime, endTime) . This means the event includes startTime , but does not include endTime . For example, the interval [10, 20) contains all times from 10...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1438 - Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

LeetCode Problem 1438 Difficulty: 🟡 Medium Topics: Array, Queue, Sliding Window, Heap (Priority Queue), Ordered Set, Monotonic Queue Solution Problem Understanding The problem asks us to find the length of the longest contiguous subarray in an integer array nums such that the absolute difference between any two elements in that subarray does not exceed a given limit . In other words, for any valid subarray, if max_val is the maximum...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2031 - Count Subarrays With More Ones Than Zeros

LeetCode Problem 2031 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding This problem asks us to count all subarrays of a binary array nums that contain more 1 s than 0 s. In other words, for any contiguous slice of the array, if the number of 1 s exceeds the number of 0 s,...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 315 - Count of Smaller Numbers After Self

LeetCode Problem 315 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding The problem asks us to compute, for every element in the array, how many elements to its right are strictly smaller than it. Given an array nums , we must return another array counts of the same length. For each index i , counts[i] represents...

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LeetCode 2035 - Partition Array Into Two Arrays to Minimize Sum Difference

LeetCode Problem 2035 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Bit Manipulation, Sorting, Ordered Set, Bitmask Solution Problem Understanding The problem gives an array nums containing exactly 2 * n integers. We must divide these integers into two separate groups, each containing exactly n elements. After forming the two groups, we compute the sum of each group and measure the absolute difference between those sums. Our...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1418 - Display Table of Food Orders in a Restaurant

LeetCode Problem 1418 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Sorting, Ordered Set Solution Problem Understanding The problem gives a list of restaurant orders. Each order contains three pieces of information: Customer name Table number Food item An order looks like this: [customerName, tableNumber, foodItem] The goal is to build a display table that summarizes how many times each food item was ordered at every table. The output format...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 352 - Data Stream as Disjoint Intervals

LeetCode Problem 352 Difficulty: 🔴 Hard Topics: Hash Table, Binary Search, Union-Find, Design, Data Stream, Ordered Set Solution LeetCode 352 - Data Stream as Disjoint Intervals Problem Understanding This problem asks us to process a stream of non-negative integers and continuously maintain a compact representation of all numbers seen so far. Instead of storing every individual number separately, we want to group consecutive numbers into disjoint intervals. An interval [start,...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 683 - K Empty Slots

LeetCode Problem 683 Difficulty: 🔴 Hard Topics: Array, Binary Indexed Tree, Segment Tree, Queue, Sliding Window, Heap (Priority Queue), Ordered Set, Monotonic Queue Solution Let's go through a complete, detailed technical solution guide for LeetCode 683 - K Empty Slots following your formatting instructions. Problem Understanding The problem asks us to find the earliest day when there are exactly k bulbs turned off between two bulbs that are turned on....

Practice › LeetCode › LeetCode 08xx ›

LeetCode 855 - Exam Room

LeetCode Problem 855 Difficulty: 🟡 Medium Topics: Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding This problem requires designing a simulation for an exam room seating arrangement. We have n seats in a single row, labeled from 0 to n - 1 . Students enter one by one, and each student chooses a seat such that the distance to the closest occupied seat is maximized. If there are multiple...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 456 - 132 Pattern

LeetCode Problem 456 Difficulty: 🟡 Medium Topics: Array, Binary Search, Stack, Monotonic Stack, Ordered Set Solution Problem Understanding The problem asks us to determine whether an array contains a specific ordering pattern called a "132 pattern". A valid 132 pattern consists of three indices i , j , and k such that: i < j < k nums[i] < nums[k] < nums[j] The name "132" comes from the relative ordering...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 220 - Contains Duplicate III

LeetCode Problem 220 Difficulty: 🔴 Hard Topics: Array, Sliding Window, Sorting, Bucket Sort, Ordered Set Solution Problem Understanding The problem asks whether there exists a pair of different indices (i, j) in the array such that two conditions are satisfied at the same time. The first condition is about index distance: $$|i - j| \leq indexDiff$$ This means the two elements must be relatively close together in the array. The...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1825 - Finding MK Average

LeetCode Problem 1825 Difficulty: 🔴 Hard Topics: Design, Queue, Heap (Priority Queue), Data Stream, Ordered Set Solution Problem Understanding The problem asks us to design a data structure that continuously receives numbers from a stream and can efficiently compute a special average called the MKAverage. For every query, we only care about the most recent m elements in the stream. From those m elements: Remove the smallest k numbers. Remove...

Practice › LeetCode › LeetCode (archived) › LeetCode 08xx ›

LeetCode 850: Rectangle Area II

Problem Restatement We are given a list of axis-aligned rectangles. Each rectangle is represented as: [x1, y1, x2, y2] where: Coordinate Meaning (x1, y1) Bottom-left corner (x2, y2) Top-right corner We need to calculate the total area covered by all rectangles. If rectangles overlap, the overlapping region should be counted only once. Since the result can be large, return it modulo: 10**9 + 7 The official problem asks for the...

Practice › LeetCode › LeetCode (archived) › LeetCode 08xx ›

LeetCode 855: Exam Room

Problem Restatement We need to design an ExamRoom class. There are n seats in one row, labeled: 0, 1, 2, ..., n - 1 When a student enters, they choose the seat that maximizes the distance to the closest occupied seat. If several seats give the same distance, the student chooses the smallest seat number. If the room is empty, the student sits at seat 0 . We need to...

Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 363: Max Sum of Rectangle No Larger Than K

Problem Restatement We are given an m x n integer matrix and an integer k . We need to find the maximum sum of any rectangle in the matrix such that the sum is no larger than k . A rectangle means a contiguous block of rows and columns. The problem guarantees that at least one rectangle has sum less than or equal to k . The official example uses...

#ordered-set

LeetCode 3885 - Design Event Manager

LeetCode 3815 - Design Auction System

LeetCode 3590 - Kth Smallest Path XOR Sum

LeetCode 3607 - Power Grid Maintenance

LeetCode 3510 - Minimum Pair Removal to Sort Array II

LeetCode 3508 - Implement Router

LeetCode 3507 - Minimum Pair Removal to Sort Array I

LeetCode 3479 - Fruits Into Baskets III

LeetCode 3477 - Fruits Into Baskets II

LeetCode 3408 - Design Task Manager

LeetCode 1847 - Closest Room

LeetCode 2612 - Minimum Reverse Operations

LeetCode 3244 - Shortest Distance After Road Addition Queries II

LeetCode 2363 - Merge Similar Items

LeetCode 2613 - Beautiful Pairs

LeetCode 2762 - Continuous Subarrays

LeetCode 1912 - Design Movie Rental System

LeetCode 2336 - Smallest Number in Infinite Set

LeetCode 2424 - Longest Uploaded Prefix

LeetCode 3391 - Design a 3D Binary Matrix with Efficient Layer Tracking

LeetCode 2426 - Number of Pairs Satisfying Inequality

LeetCode 2179 - Count Good Triplets in an Array

LeetCode 2349 - Design a Number Container System

LeetCode 2817 - Minimum Absolute Difference Between Elements With Constraint

LeetCode 2102 - Sequentially Ordinal Rank Tracker

LeetCode 3245 - Alternating Groups III

LeetCode 1902 - Depth of BST Given Insertion Order

LeetCode 3109 - Find the Index of Permutation

LeetCode 3092 - Most Frequent IDs

LeetCode 2382 - Maximum Segment Sum After Removals

LeetCode 2251 - Number of Flowers in Full Bloom

LeetCode 2213 - Longest Substring of One Repeating Character

LeetCode 3073 - Maximum Increasing Triplet Value

LeetCode 2713 - Maximum Strictly Increasing Cells in a Matrix

LeetCode 2659 - Make Array Empty

LeetCode 2519 - Count the Number of K-Big Indices

LeetCode 2158 - Amount of New Area Painted Each Day

LeetCode 2353 - Design a Food Rating System

LeetCode 3369 - Design an Array Statistics Tracker

LeetCode 2276 - Count Integers in Intervals

LeetCode 3102 - Minimize Manhattan Distances

LeetCode 715 - Range Module

LeetCode 1818 - Minimum Absolute Sum Difference

LeetCode 493 - Reverse Pairs

LeetCode 699 - Falling Squares

LeetCode 327 - Count of Range Sum

LeetCode 975 - Odd Even Jump

LeetCode 1348 - Tweet Counts Per Frequency

LeetCode 497 - Random Point in Non-overlapping Rectangles

LeetCode 218 - The Skyline Problem

LeetCode 895 - Maximum Frequency Stack

LeetCode 2034 - Stock Price Fluctuation

LeetCode 1606 - Find Servers That Handled Most Number of Requests

LeetCode 363 - Max Sum of Rectangle No Larger Than K

LeetCode 1675 - Minimize Deviation in Array

LeetCode 2021 - Brightest Position on Street

LeetCode 1649 - Create Sorted Array through Instructions

LeetCode 850 - Rectangle Area II

LeetCode 731 - My Calendar II

LeetCode 732 - My Calendar III

LeetCode 635 - Design Log Storage System

LeetCode 716 - Max Stack

LeetCode 729 - My Calendar I

LeetCode 1438 - Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

LeetCode 2031 - Count Subarrays With More Ones Than Zeros

LeetCode 315 - Count of Smaller Numbers After Self

LeetCode 2035 - Partition Array Into Two Arrays to Minimize Sum Difference

LeetCode 1418 - Display Table of Food Orders in a Restaurant

LeetCode 352 - Data Stream as Disjoint Intervals

LeetCode 683 - K Empty Slots

LeetCode 855 - Exam Room

LeetCode 456 - 132 Pattern

LeetCode 220 - Contains Duplicate III

LeetCode 1825 - Finding MK Average

LeetCode 850: Rectangle Area II

LeetCode 855: Exam Room

LeetCode 363: Max Sum of Rectangle No Larger Than K