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Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 38xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

Practice › LeetCode › LeetCode 35xx ›

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...

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 34xx ›

LeetCode 3420 - Count Non-Decreasing Subarrays After K Operations

LeetCode Problem 3420 Difficulty: 🔴 Hard Topics: Array, Stack, Segment Tree, Queue, Sliding Window, Monotonic Stack, Monotonic Queue Solution Problem Understanding You are given an array nums and a budget of at most k increment operations. For any chosen subarray, you may repeatedly pick an element inside that subarray and increase it by 1 . The goal is to determine whether that subarray can be transformed into a non-decreasing array...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3191 - Minimum Operations to Make Binary Array Elements Equal to One I

LeetCode Problem 3191 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Queue, Sliding Window, Prefix Sum Solution Problem Understanding We are given a binary array nums consisting only of 0s and 1s. We are allowed to perform an operation any number of times: choose any three consecutive elements and flip them, meaning 0 becomes 1 and 1 becomes 0. The goal is to determine the minimum number of such operations required...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2944 - Minimum Number of Coins for Fruits

LeetCode Problem 2944 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Queue, Heap (Priority Queue), Monotonic Queue Solution Problem Understanding This problem asks us to determine the minimum number of coins required to acquire all fruits in a market where buying a fruit grants a special reward. You are given a 0-indexed array prices , where prices[i] represents the cost of purchasing the (i + 1) th fruit. The important twist...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2073 - Time Needed to Buy Tickets

LeetCode Problem 2073 Difficulty: 🟢 Easy Topics: Array, Queue, Simulation Solution Problem Understanding This problem describes a queue of n people, each wanting to buy a certain number of tickets. The input is an array tickets where tickets[i] represents how many tickets the i-th person wants. The process works like a real-life queue: each person buys one ticket at a time , taking exactly 1 second per ticket , and...

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 25xx ›

LeetCode 2526 - Find Consecutive Integers from a Data Stream

LeetCode Problem 2526 Difficulty: 🟡 Medium Topics: Hash Table, Design, Queue, Counting, Data Stream Solution Problem Understanding The problem asks us to design a data structure that continuously processes a stream of integers and determines whether the most recent k integers are all equal to a specific target value. We are given two parameters when initializing the data structure: value , which represents the integer we are interested in tracking....

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2444 - Count Subarrays With Fixed Bounds

LeetCode Problem 2444 Difficulty: 🔴 Hard Topics: Array, Queue, Sliding Window, Monotonic Queue Solution Problem Understanding This problem asks us to count how many contiguous subarrays satisfy two exact boundary conditions at the same time: The minimum element in the subarray must be exactly minK . The maximum element in the subarray must be exactly maxK . The key detail is that these are exact matches , not inequalities. A...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2327 - Number of People Aware of a Secret

LeetCode Problem 2327 Difficulty: 🟡 Medium Topics: Dynamic Programming, Queue, Simulation Solution Problem Understanding The problem describes how a secret spreads over time. On day 1 , exactly one person knows the secret. Every person who learns the secret behaves according to two rules: They must wait delay days before they can begin sharing the secret. They forget the secret after forget days, and once they forget it, they can...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2534 - Time Taken to Cross the Door

LeetCode Problem 2534 Difficulty: 🔴 Hard Topics: Array, Queue, Simulation Solution Problem Understanding This problem asks us to simulate how people pass through a single door over time while following a specific priority policy. Every person arrives at a certain second and wants to either enter or exit. Only one person may use the door per second, and when multiple people are waiting, the rules determine who gets priority. The...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2071 - Maximum Number of Tasks You Can Assign

LeetCode Problem 2071 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Greedy, Queue, Sorting, Monotonic Queue Solution Problem Understanding This problem asks us to maximize the number of tasks that can be completed using a group of workers, where each worker can perform at most one task. Each task has a required strength value, and each worker has a current strength value. A worker can complete a task if...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2407 - Longest Increasing Subsequence II

LeetCode Problem 2407 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Dynamic Programming, Binary Indexed Tree, Segment Tree, Queue, Monotonic Queue Solution Problem Understanding The problem asks us to find the length of the longest subsequence in an integer array nums such that the subsequence is strictly increasing and the difference between consecutive elements does not exceed a given integer k . A subsequence is formed by deleting zero or...

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 31xx ›

LeetCode 3117 - Minimum Sum of Values by Dividing Array

LeetCode Problem 3117 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Bit Manipulation, Segment Tree, Queue Solution Problem Understanding This problem asks us to partition an array nums into exactly m contiguous subarrays such that the bitwise AND of elements in the i-th subarray equals andValues[i] . Once partitioned, we sum the last elements of each subarray to compute a total value, and the goal is to minimize this...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2398 - Maximum Number of Robots Within Budget

LeetCode Problem 2398 Difficulty: 🔴 Hard Topics: Array, Binary Search, Queue, Sliding Window, Heap (Priority Queue), Prefix Sum, Monotonic Queue Solution Problem Understanding This problem asks us to determine the maximum number of consecutive robots that can be run without exceeding a given budget. We are given two arrays of length n : chargeTimes and runningCosts . For any consecutive subset of k robots, the total cost is computed as:...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2945 - Find Maximum Non-decreasing Array Length

LeetCode Problem 2945 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Stack, Queue, Monotonic Stack, Monotonic Queue Solution Problem Understanding This problem asks us to determine the maximum length of a non-decreasing array that can be obtained from a given integer array nums by performing a sequence of subarray sum operations . In each operation, we can choose any contiguous subarray, replace it with a single element equal to...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2969 - Minimum Number of Coins for Fruits II

LeetCode Problem 2969 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Queue, Heap (Priority Queue), Monotonic Queue Solution Problem Understanding The problem asks us to determine the minimum number of coins required to purchase all fruits in a market, given a special offer. You are provided with a 1-indexed array prices , where prices[i] denotes the number of coins needed to buy the ith fruit. The market has a special offer:...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2528 - Maximize the Minimum Powered City

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

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 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 03xx ›

LeetCode 353 - Design Snake Game

LeetCode Problem 353 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Queue, Simulation Solution Problem Understanding The problem asks us to design a mutable data structure that simulates the classic Snake game. The game is played on a rectangular grid with dimensions height x width . The snake starts at the top-left corner (0, 0) and initially has length 1 . The game receives a predefined sequence of food positions....

Practice › LeetCode › LeetCode 09xx ›

LeetCode 933 - Number of Recent Calls

LeetCode Problem 933 Difficulty: 🟢 Easy Topics: Design, Queue, Data Stream Solution Problem Understanding The problem asks us to implement a class RecentCounter that tracks the number of requests (or pings) made in the last 3000 milliseconds. Every time the ping(t) method is called with a time t , we are asked to return how many requests occurred within the time interval [t - 3000, t] . The class starts...

Practice › LeetCode › LeetCode 08xx ›

LeetCode 862 - Shortest Subarray with Sum at Least K

LeetCode Problem 862 Difficulty: 🔴 Hard Topics: Array, Binary Search, Queue, Sliding Window, Heap (Priority Queue), Prefix Sum, Monotonic Queue Solution Problem Understanding The problem asks us to find the length of the shortest contiguous subarray whose sum is at least k . We are given an integer array nums , which may contain both positive and negative numbers, and an integer k . We must return the minimum length...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1823 - Find the Winner of the Circular Game

LeetCode Problem 1823 Difficulty: 🟡 Medium Topics: Array, Math, Recursion, Queue, Simulation Solution Problem Understanding The problem describes a variation of the classic Josephus problem. We have n friends sitting in a circle, numbered 1 through n clockwise. Starting from the first friend, we count k friends clockwise (inclusive of the starting friend). The friend at the k -th position is removed from the circle. The counting then resumes from...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 387 - First Unique Character in a String

LeetCode Problem 387 Difficulty: 🟢 Easy Topics: Hash Table, String, Queue, Counting Solution Problem Understanding The problem gives us a string s consisting only of lowercase English letters. We must find the index of the first character that appears exactly once in the entire string. If every character appears more than once, we return -1 . The key detail is that we are looking for the first non-repeating character based...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1499 - Max Value of Equation

LeetCode Problem 1499 Difficulty: 🔴 Hard Topics: Array, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue Solution This guide will focus on the optimal monotonic queue solution, which achieves linear time complexity and is necessary to handle the input size limit of 10^5 . Problem Understanding We are given a list of 2D points sorted in strictly increasing order by their x-coordinate. Each point is represented as [xi, yi] ,...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 346 - Moving Average from Data Stream

LeetCode Problem 346 Difficulty: 🟢 Easy Topics: Array, Design, Queue, Data Stream Solution Problem Understanding The problem asks us to design a data structure that continuously receives integers from a stream and returns the average of the most recent values within a fixed-size sliding window. A sliding window means that we only care about the latest size elements. As new values arrive, older values eventually fall out of the window...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1696 - Jump Game VI

LeetCode Problem 1696 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Queue, Heap (Priority Queue), Monotonic Queue Solution Problem Understanding The problem gives us an integer array nums and a maximum jump distance k . We start at index 0 , and from any position i , we may jump forward to any index between i + 1 and i + k , as long as the destination remains inside the...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1425 - Constrained Subsequence Sum

LeetCode Problem 1425 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue Solution That is a long, structured reference document. To make sure I target the exact problem correctly, please confirm the LeetCode problem number and title one more time. You mentioned LeetCode 1425 - Constrained Subsequence Sum , but the required output format is extensive, and I want to avoid generating a full...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 379 - Design Phone Directory

LeetCode Problem 379 Difficulty: 🟡 Medium Topics: Array, Hash Table, Linked List, Design, Queue Solution Problem Understanding The problem asks us to design a data structure that manages a fixed pool of phone numbers. Initially, every number from 0 to maxNumbers - 1 is available. The directory must support three operations efficiently. The get() operation should assign and return an available number. If no numbers remain, it should return -1...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 341 - Flatten Nested List Iterator

LeetCode Problem 341 Difficulty: 🟡 Medium Topics: Stack, Tree, Depth-First Search, Design, Queue, Iterator Solution Problem Understanding This problem asks us to design an iterator that can traverse a deeply nested list structure as if it were a flat list of integers. The input is not a normal array. Each element inside nestedList can be one of two things: A single integer Another list containing more NestedInteger objects Those nested...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 649 - Dota2 Senate

LeetCode Problem 649 Difficulty: 🟡 Medium Topics: String, Greedy, Queue Solution Problem Understanding The problem describes a turn-based voting process between two parties in the Dota2 senate, the Radiant party represented by 'R' and the Dire party represented by 'D' . We are given a string senate where each character represents a senator and their party affiliation. The order of characters in the string is important because senators act sequentially...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1429 - First Unique Number

LeetCode Problem 1429 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Queue, Data Stream Solution Problem Understanding The problem requires designing a data structure that can efficiently maintain and retrieve the first unique integer in a queue of numbers. You are given an initial list of integers, and after that, the data structure should support two operations efficiently: retrieving the first unique number ( showFirstUnique ) and adding a new...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1687 - Delivering Boxes from Storage to Ports

LeetCode Problem 1687 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Segment Tree, Queue, Heap (Priority Queue), Prefix Sum, Monotonic Queue Solution Problem Understanding This problem asks us to minimize the total number of ship trips required to deliver boxes from storage to ports, while respecting two constraints: The ship can carry at most maxBoxes boxes at once. The total weight of the loaded boxes cannot exceed maxWeight . The boxes...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 225 - Implement Stack using Queues

LeetCode Problem 225 Difficulty: 🟢 Easy Topics: Stack, Design, Queue Solution Problem Understanding The problem asks us to implement a stack data structure while using only queue operations internally. A stack follows the Last-In-First-Out, or LIFO, principle. This means the most recently inserted element must be removed first. In contrast, a queue follows the First-In-First-Out, or FIFO, principle, where elements leave in the same order they entered. We must design...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 950 - Reveal Cards In Increasing Order

LeetCode Problem 950 Difficulty: 🟡 Medium Topics: Array, Queue, Sorting, Simulation Solution Problem Understanding The problem gives us a deck of unique integer cards and asks us to arrange the deck so that a very specific reveal process produces the cards in increasing order. The reveal process works like this: Reveal the top card and remove it from the deck. Move the next top card to the bottom of the...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 995 - Minimum Number of K Consecutive Bit Flips

LeetCode Problem 995 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Queue, Sliding Window, Prefix Sum Solution Problem Understanding The problem gives us a binary array nums consisting of 0s and 1s and an integer k . The task is to transform the array so that all elements are 1 s using the minimum number of operations called k-bit flips . Each k-bit flip consists of picking a contiguous subarray of...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 936 - Stamping The Sequence

LeetCode Problem 936 Difficulty: 🔴 Hard Topics: String, Stack, Greedy, Queue Solution Problem Understanding This problem asks us to reconstruct a target string by repeatedly applying a smaller string called stamp . We begin with a string s that has the same length as target , but every character is initially '?' . In one operation, we may place the stamp string onto any valid position in s , and...

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 02xx ›

LeetCode 232 - Implement Queue using Stacks

LeetCode Problem 232 Difficulty: 🟢 Easy Topics: Stack, Design, Queue Solution Problem Understanding The problem asks us to implement a queue using only stack operations. A queue follows the FIFO, First In First Out, principle. The first element inserted into the queue must be the first element removed. In contrast, a stack follows the LIFO, Last In First Out, principle, where the most recently inserted element is removed first. We...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 239 - Sliding Window Maximum

LeetCode Problem 239 Difficulty: 🔴 Hard Topics: Array, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue Solution LeetCode 239 - Sliding Window Maximum Problem Understanding The problem gives us an integer array nums and a window size k . A sliding window of length k starts at the beginning of the array and moves one position to the right at a time. For every position of this window, we must...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1700 - Number of Students Unable to Eat Lunch

LeetCode Problem 1700 Difficulty: 🟢 Easy Topics: Array, Stack, Queue, Simulation Solution Problem Understanding This problem simulates a school cafeteria where students line up to take sandwiches from a stack. Each student has a preference for either a circular sandwich ( 0 ) or a square sandwich ( 1 ). The sandwiches are arranged in a stack where the first element of the sandwiches array represents the top of the...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 362 - Design Hit Counter

LeetCode Problem 362 Difficulty: 🟡 Medium Topics: Array, Binary Search, Design, Queue, Data Stream Solution Problem Understanding The problem asks us to design a data structure that tracks how many events, called "hits", occurred during the last 5 minutes. Every hit comes with a timestamp measured in seconds, and timestamps are guaranteed to arrive in chronological order. The class must support three operations: hit(timestamp) records a new hit at the...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 281 - Zigzag Iterator

LeetCode Problem 281 Difficulty: 🟡 Medium Topics: Array, Design, Queue, Iterator Solution Problem Understanding The problem asks us to design an iterator that alternates between two input arrays, returning elements in a cyclic or zigzag order. Instead of consuming all elements from the first vector and then moving to the second vector, we must switch back and forth between them whenever possible. For example, if the input vectors are [1,...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 641 - Design Circular Deque

LeetCode Problem 641 Difficulty: 🟡 Medium Topics: Array, Linked List, Design, Queue Solution Problem Understanding The problem asks us to design a circular double-ended queue, also called a deque. A deque is a data structure that allows insertion and deletion from both the front and the rear. Unlike a normal queue, which only supports enqueue at the back and dequeue at the front, a deque supports operations at both ends...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 622 - Design Circular Queue

LeetCode Problem 622 Difficulty: 🟡 Medium Topics: Array, Linked List, Design, Queue Solution Problem Understanding The problem asks us to implement a circular queue, a fixed-size queue where the end wraps back to the start to efficiently reuse empty space. In a normal queue implemented with an array, once the array fills, even if elements are dequeued from the front, new elements cannot be enqueued without shifting the array. A...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 918 - Maximum Sum Circular Subarray

LeetCode Problem 918 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Dynamic Programming, Queue, Monotonic Queue Solution Problem Understanding The problem asks for the maximum sum of a subarray in a circular array . In simpler terms, we are given a list of integers nums where the end of the list wraps around to the start. We need to find a contiguous section of this list that has the highest...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1670 - Design Front Middle Back Queue

LeetCode Problem 1670 Difficulty: 🟡 Medium Topics: Array, Linked List, Design, Queue, Doubly-Linked List, Data Stream Solution Problem Understanding The problem is asking us to design a specialized queue that allows insertions and removals not only at the front and back, but also at the middle of the queue. We need to maintain the queue such that we can efficiently access and modify elements at these three positions. The middle...

Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 950: Reveal Cards In Increasing Order

Problem Restatement We are given an array: deck Each card has a unique integer. We may reorder the deck however we want. The first element of the returned array is considered the top of the deck. Then the reveal process works like this: Reveal the top card and remove it. If cards remain, move the next top card to the bottom. Repeat until all cards are revealed. Return an initial...

Practice › LeetCode › LeetCode (archived) › LeetCode 07xx ›

LeetCode 792: Number of Matching Subsequences

Problem Restatement We are given a string s and an array of strings words . We need to return how many strings in words are subsequences of s . A subsequence is formed by deleting zero or more characters from a string without changing the order of the remaining characters. For example, "ace" is a subsequence of "abcde" . Input and Output Item Meaning Input A string s and a...

Practice › LeetCode › LeetCode (archived) › LeetCode 06xx ›

LeetCode 622: Design Circular Queue

Problem Restatement We need to design a circular queue. A queue follows FIFO order: first in, first out. A circular queue uses a fixed-size array, but when the end of the array is reached, the next position wraps around to the beginning. This lets the queue reuse empty space created by earlier removals. The class must support these operations: Operation Meaning MyCircularQueue(k) Create a queue with capacity k enQueue(value) Insert...

Practice › LeetCode › LeetCode (archived) › LeetCode 06xx ›

LeetCode 649: Dota2 Senate

Problem Restatement We are given a string senate . Each character represents one senator: Character Party "R" Radiant "D" Dire The voting process happens in rounds from left to right. On a senator's turn, if they still have voting rights, they can ban one senator from the opposite party. A banned senator loses voting rights for the current and all future rounds. If all remaining senators with voting rights belong...

Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 936: Stamping The Sequence

Problem Restatement We are given two strings: stamp target Initially, we start with a string made entirely of question marks: "?????" with the same length as target . In one move, we may place the stamp string over any position and overwrite the characters. For example: stamp = "abc" before = "?????" after = "??abc" The goal is to build target . We must return a sequence of stamping positions...

Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 958: Check Completeness of a Binary Tree

Problem Restatement We are given the root of a binary tree. We need to determine whether the tree is a complete binary tree. A complete binary tree has these properties: Every level except possibly the last is completely filled. All nodes in the last level are as far left as possible. Return true if the tree is complete. Otherwise, return false . The official problem states this exact definition: every...

Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 933: Number of Recent Calls

Problem Restatement We need to implement a class called RecentCounter . It supports one main operation: ping(t) Each call records a request at time t , measured in milliseconds. After recording the request, ping(t) must return how many requests happened in the time range: [t - 3000, t] The current request is included. The problem guarantees that every new t is strictly larger than the previous one. The official statement...

Practice › LeetCode › LeetCode (archived) › LeetCode 06xx ›

LeetCode 641: Design Circular Deque

Problem Restatement We need to design a circular double-ended queue. A deque supports insertion and deletion from both ends: Operation Meaning insertFront(value) Add a value to the front insertLast(value) Add a value to the rear deleteFront() Remove the front value deleteLast() Remove the rear value getFront() Read the front value getRear() Read the rear value The deque has a fixed maximum capacity k . If we try to insert into...

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LeetCode 637: Average of Levels in Binary Tree

Problem Restatement We are given the root of a binary tree. We need to return an array where each element is the average value of all nodes on one level of the tree. The first value is the average of the root level. The second value is the average of the next level. The result continues from top to bottom. Answers within 10^-5 of the actual answer are accepted. The...

Practice › LeetCode › LeetCode (archived) › LeetCode 06xx ›

LeetCode 662: Maximum Width of Binary Tree

Problem Restatement We are given the root of a binary tree. We need to return the maximum width among all levels of the tree. The width of a level is measured between the leftmost and rightmost non-null nodes on that level. However, null nodes between those two endpoints are also counted, as if the tree were placed inside a complete binary tree. Input and Output Item Meaning Input The root...

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LeetCode 444: Sequence Reconstruction

Problem Restatement We are given: Name Meaning nums The target sequence sequences A list of subsequences The array nums is a permutation of integers from 1 to n . Each sequence in sequences is a subsequence of nums . We need to check whether nums is the only shortest supersequence that contains every sequence in sequences as a subsequence. A supersequence means it contains another sequence in the same relative...

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LeetCode 225: Implement Stack using Queues

Problem Restatement We need to implement a stack using only queues. A stack follows LIFO order: last in, first out A queue follows FIFO order: first in, first out We need to implement the class MyStack with these operations: Method Meaning push(x) Push x onto the stack pop() Remove and return the top element top() Return the top element without removing it empty() Return whether the stack is empty The...

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LeetCode 346: Moving Average from Data Stream

Problem Restatement We need to design a class that calculates the moving average of the last size values in a data stream. The class supports: Method Meaning MovingAverage(size) Initializes the moving window size next(val) Adds a value and returns the current moving average The moving average is computed over the most recent values currently inside the window. If fewer than size values have appeared so far, average over all available...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 286: Walls and Gates

Problem Restatement We are given an m x n grid called rooms . Each cell has one of three values: Value Meaning -1 Wall or obstacle 0 Gate 2147483647 Empty room, also called INF We need to fill each empty room with the distance to its nearest gate. Distance is the number of steps needed to reach a gate by moving only up, down, left, or right. If an empty...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 111: Minimum Depth of Binary Tree

Problem Restatement We are given the root of a binary tree. We need to return its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. A leaf is a node with no children. For this tree: 3 / \ 9 20 / \ 15 7 The nearest leaf is 9 . The path is: 3...

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LeetCode 362: Design Hit Counter

Problem Restatement We need to design a hit counter. The counter supports two operations: Method Meaning hit(timestamp) Record one hit at timestamp getHits(timestamp) Return how many hits happened in the past 300 seconds The timestamp is given in seconds. Calls arrive in chronological order, so timestamps are monotonically increasing. Multiple hits may happen at the same timestamp. The time window is the past 5 minutes, which means the past 300...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 107: Binary Tree Level Order Traversal II

Problem Restatement We are given the root of a binary tree. We need to return the node values level by level, but from bottom to top. Inside each level, values must still be ordered from left to right. The official problem asks for the bottom-up level order traversal of the binary tree's node values, from leaf level to root level. For this tree: 3 / \ 9 20 / \...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 281: Zigzag Iterator

Problem Restatement We are given two integer lists, v1 and v2 . We need to implement an iterator that returns their elements alternately. For example: v1 = [1, 2] v2 = [3, 4, 5, 6] The iterator should return: 1, 3, 2, 4, 5, 6 Once one list runs out, we continue returning elements from the other list. The class has three operations: ZigzagIterator(v1, v2) next() hasNext() The source statement...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 232: Implement Queue using Stacks

Problem Restatement We need to implement a queue using only standard stack operations. The queue must support: Operation Meaning push(x) Add x to the back of the queue pop() Remove and return the front element peek() Return the front element without removing it empty() Return whether the queue is empty A queue follows FIFO order: First In, First Out A stack follows LIFO order: Last In, First Out The challenge...

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

LeetCode 358: Rearrange String k Distance Apart

Problem Restatement We are given a non-empty lowercase string s and an integer k . We need to rearrange the characters of s so that the same characters are at least distance k from each other. If this is possible, return any valid rearranged string. If this is impossible, return an empty string "" . For example, if character a appears at index i , then the next a can...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 103: Binary Tree Zigzag Level Order Traversal

Problem Restatement We are given the root of a binary tree. We need to return the values level by level. The first level is read from left to right, the second level from right to left, the third level from left to right, and so on. The official problem asks for the zigzag level order traversal of a binary tree's node values. For this tree: 3 / \ 9 20...

Practice › LeetCode › LeetCode (archived) › LeetCode 04xx ›

LeetCode 429: N-ary Tree Level Order Traversal

Problem Restatement We are given the root of an N-ary tree. We need to return the level order traversal of its node values. Level order traversal means: Visit all nodes on level 0 Then all nodes on level 1 Then all nodes on level 2 Continue until the tree is finished For each level, we store the node values in a separate list. The final answer is therefore a list...

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

LeetCode 379: Design Phone Directory

Problem Restatement We need to design a phone directory. The directory starts with maxNumbers available numbers: 0, 1, 2, ..., maxNumbers - 1 We need to support three operations: Operation Meaning get() Return an available number and mark it as used check(number) Return whether number is available release(number) Make a used number available again If no number is available, get() must return -1 . The problem statement defines these operations...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 102: Binary Tree Level Order Traversal

Problem Restatement We are given the root of a binary tree. We need to return the node values level by level, from left to right inside each level. The official problem asks for the level order traversal of the binary tree's node values. For this tree: 3 / \ 9 20 / \ 15 7 The answer is: [[3], [9, 20], [15, 7]] Each inner list contains one tree level....

Wiki › Algorithms › 02. Data Structures › 1. Core Data Structures and Operations ›

1.4 Queues and Deques

1.4 Queues and deques, 35 index slug name 1 array-queue Array Queue 2 circular-queue Circular Queue 3 linked-queue Linked Queue 4 deque Deque 5 priority-queue-basic Basic Priority Queue 6 queue-enqueue-dequeue Enqueue Dequeue 7 queue-two-stacks Queue via Stacks 8 deque-array Array Deque 9 deque-linked Linked Deque 10 monotonic-queue Monotonic Queue 11 blocking-queue Blocking Queue 12 lock-free-queue Lock Free Queue 13 queue-buffer Buffer Queue 14 queue-scheduler Scheduler Queue 15 queue-bfs BFS Queue...

#queue

LeetCode 3845 - Maximum Subarray XOR with Bounded Range

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

LeetCode 3829 - Design Ride Sharing System

LeetCode 3826 - Minimum Partition Score

LeetCode 3589 - Count Prime-Gap Balanced Subarrays

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

LeetCode 3508 - Implement Router

LeetCode 3420 - Count Non-Decreasing Subarrays After K Operations

LeetCode 3191 - Minimum Operations to Make Binary Array Elements Equal to One I

LeetCode 2944 - Minimum Number of Coins for Fruits

LeetCode 2073 - Time Needed to Buy Tickets

LeetCode 2762 - Continuous Subarrays

LeetCode 2526 - Find Consecutive Integers from a Data Stream

LeetCode 2444 - Count Subarrays With Fixed Bounds

LeetCode 2327 - Number of People Aware of a Secret

LeetCode 2534 - Time Taken to Cross the Door

LeetCode 2071 - Maximum Number of Tasks You Can Assign

LeetCode 2407 - Longest Increasing Subsequence II

LeetCode 3369 - Design an Array Statistics Tracker

LeetCode 3117 - Minimum Sum of Values by Dividing Array

LeetCode 2398 - Maximum Number of Robots Within Budget

LeetCode 2945 - Find Maximum Non-decreasing Array Length

LeetCode 2969 - Minimum Number of Coins for Fruits II

LeetCode 2528 - Maximize the Minimum Powered City

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

LeetCode 1825 - Finding MK Average

LeetCode 353 - Design Snake Game

LeetCode 933 - Number of Recent Calls

LeetCode 862 - Shortest Subarray with Sum at Least K

LeetCode 1823 - Find the Winner of the Circular Game

LeetCode 387 - First Unique Character in a String

LeetCode 1499 - Max Value of Equation

LeetCode 346 - Moving Average from Data Stream

LeetCode 1696 - Jump Game VI

LeetCode 1425 - Constrained Subsequence Sum

LeetCode 379 - Design Phone Directory

LeetCode 341 - Flatten Nested List Iterator

LeetCode 649 - Dota2 Senate

LeetCode 1429 - First Unique Number

LeetCode 1687 - Delivering Boxes from Storage to Ports

LeetCode 225 - Implement Stack using Queues

LeetCode 950 - Reveal Cards In Increasing Order

LeetCode 995 - Minimum Number of K Consecutive Bit Flips

LeetCode 936 - Stamping The Sequence

LeetCode 683 - K Empty Slots

LeetCode 232 - Implement Queue using Stacks

LeetCode 239 - Sliding Window Maximum

LeetCode 1700 - Number of Students Unable to Eat Lunch

LeetCode 362 - Design Hit Counter

LeetCode 281 - Zigzag Iterator

LeetCode 641 - Design Circular Deque

LeetCode 622 - Design Circular Queue

LeetCode 918 - Maximum Sum Circular Subarray

LeetCode 1670 - Design Front Middle Back Queue

LeetCode 950: Reveal Cards In Increasing Order

LeetCode 792: Number of Matching Subsequences

LeetCode 622: Design Circular Queue

LeetCode 649: Dota2 Senate

LeetCode 936: Stamping The Sequence

LeetCode 958: Check Completeness of a Binary Tree

LeetCode 933: Number of Recent Calls

LeetCode 641: Design Circular Deque

LeetCode 637: Average of Levels in Binary Tree

LeetCode 662: Maximum Width of Binary Tree

LeetCode 444: Sequence Reconstruction

LeetCode 225: Implement Stack using Queues

LeetCode 346: Moving Average from Data Stream

LeetCode 286: Walls and Gates

LeetCode 111: Minimum Depth of Binary Tree

LeetCode 362: Design Hit Counter

LeetCode 107: Binary Tree Level Order Traversal II

LeetCode 281: Zigzag Iterator

LeetCode 232: Implement Queue using Stacks

LeetCode 358: Rearrange String k Distance Apart

LeetCode 103: Binary Tree Zigzag Level Order Traversal

LeetCode 429: N-ary Tree Level Order Traversal

LeetCode 379: Design Phone Directory

LeetCode 102: Binary Tree Level Order Traversal

1.4 Queues and Deques