doubly-linked-list

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 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 32xx ›

LeetCode 3263 - Convert Doubly Linked List to Array I

LeetCode Problem 3263 Difficulty: 🟢 Easy Topics: Array, Linked List, Doubly-Linked List Solution Problem Understanding The problem asks us to convert a doubly linked list into a standard integer array while preserving the order of elements. In a doubly linked list, each node contains a value ( val ) and two pointers: next (pointing to the next node) and prev (pointing to the previous node). The input is a reference...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2296 - Design a Text Editor

LeetCode Problem 2296 Difficulty: 🔴 Hard Topics: Linked List, String, Stack, Design, Simulation, Doubly-Linked List Solution Problem Understanding This problem asks us to design a simplified text editor that supports four operations: Inserting text at the current cursor position Deleting characters to the left of the cursor Moving the cursor left Moving the cursor right The cursor behaves exactly like a cursor in a normal text editor. It always sits...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3294 - Convert Doubly Linked List to Array II

LeetCode Problem 3294 Difficulty: 🟡 Medium Topics: Array, Linked List, Doubly-Linked List Solution Problem Understanding This problem gives us a pointer to an arbitrary node inside a doubly linked list. Unlike many linked list problems, we are not guaranteed to receive the head of the list. Instead, we may receive any node somewhere in the middle or even the tail. A doubly linked list node contains three fields: val ,...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1472 - Design Browser History

LeetCode Problem 1472 Difficulty: 🟡 Medium Topics: Array, Linked List, Stack, Design, Doubly-Linked List, Data Stream Solution Problem Understanding The problem is asking us to simulate a single-tab browser with a history mechanism. You start on a homepage , and from there, you can visit new URLs, back track a certain number of steps, or forward a certain number of steps. The inputs consist of method calls: BrowserHistory(homepage) initializes the...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1797 - Design Authentication Manager

LeetCode Problem 1797 Difficulty: 🟡 Medium Topics: Hash Table, Linked List, Design, Doubly-Linked List Solution Problem Understanding The problem asks us to design an authentication system that manages tokens with expiration times. Each token is valid for a fixed timeToLive seconds starting from the moment it is generated or renewed. The system must support three operations: generating a new token, renewing an existing unexpired token, and counting the number of...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 460 - LFU Cache

LeetCode Problem 460 Difficulty: 🔴 Hard Topics: Hash Table, Linked List, Design, Doubly-Linked List Solution Problem Understanding The problem asks us to design a cache that supports two operations: get(key) returns the value associated with a key if it exists, otherwise -1 put(key, value) inserts or updates a key-value pair Unlike a normal cache, eviction is not based only on recency. Instead, this cache uses the Least Frequently Used policy....

Practice › LeetCode › LeetCode 04xx ›

LeetCode 426 - Convert Binary Search Tree to Sorted Doubly Linked List

LeetCode Problem 426 Difficulty: 🟡 Medium Topics: Linked List, Stack, Tree, Depth-First Search, Binary Search Tree, Binary Tree, Doubly-Linked List Solution Problem Understanding The problem asks us to transform a Binary Search Tree, abbreviated as BST, into a sorted circular doubly linked list. The transformation must happen in place, meaning we are not allowed to create entirely new nodes for the linked list. Instead, we reuse the existing tree nodes...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1756 - Design Most Recently Used Queue

LeetCode Problem 1756 Difficulty: 🟡 Medium Topics: Array, Linked List, Divide and Conquer, Design, Simulation, Doubly-Linked List Solution Problem Understanding The problem asks us to design a special queue called an "Most Recently Used Queue", abbreviated as MRUQueue. Initially, the queue contains the integers from 1 to n in increasing order. The key operation is fetch(k) , where k is 1-indexed. This operation does two things: It finds the kth...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 432 - All O`one Data Structure

LeetCode Problem 432 Difficulty: 🔴 Hard Topics: Hash Table, Linked List, Design, Doubly-Linked List Solution Problem Understanding The problem asks us to design a special data structure that stores string keys together with their occurrence counts. The structure must support incrementing and decrementing counts, while also being able to instantly retrieve one key with the maximum count and one key with the minimum count. Unlike ordinary frequency counting problems, this...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 430 - Flatten a Multilevel Doubly Linked List

LeetCode Problem 430 Difficulty: 🟡 Medium Topics: Linked List, Depth-First Search, Doubly-Linked List Solution Problem Understanding The problem gives us a special type of doubly linked list where every node contains four fields: val prev next child The next and prev pointers behave exactly like a normal doubly linked list. The extra child pointer introduces another linked list that branches downward from the current node. That child list can itself...

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 01xx ›

LeetCode 146 - LRU Cache

LeetCode Problem 146 Difficulty: 🟡 Medium Topics: Hash Table, Linked List, Design, Doubly-Linked List Solution Problem Understanding The problem asks us to design an efficient cache that follows the Least Recently Used, or LRU, eviction policy. A cache stores a limited number of key-value pairs. When the cache reaches its maximum capacity and a new item must be inserted, the least recently used item should be removed first. The class...

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 04xx ›

LeetCode 432: All O'one Data Structure

Problem Restatement We need to design a data structure that stores string counts. It must support these operations: Operation Meaning inc(key) Increase key count by 1 ; insert it with count 1 if missing dec(key) Decrease key count by 1 ; remove it if count becomes 0 getMaxKey() Return any key with the largest count getMinKey() Return any key with the smallest count If the data structure is empty, both...

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

LeetCode 430: Flatten a Multilevel Doubly Linked List

Problem Restatement We are given the head of a multilevel doubly linked list. Each node has four fields: Field Meaning val Node value prev Previous node on the same level next Next node on the same level child Head of another doubly linked list The child list can also contain nodes with their own child lists. We need to flatten everything into one single-level doubly linked list. When a node...

#doubly-linked-list

LeetCode 3510 - Minimum Pair Removal to Sort Array II

LeetCode 3507 - Minimum Pair Removal to Sort Array I

LeetCode 3263 - Convert Doubly Linked List to Array I

LeetCode 2296 - Design a Text Editor

LeetCode 3294 - Convert Doubly Linked List to Array II

LeetCode 1472 - Design Browser History

LeetCode 1797 - Design Authentication Manager

LeetCode 460 - LFU Cache

LeetCode 426 - Convert Binary Search Tree to Sorted Doubly Linked List

LeetCode 1756 - Design Most Recently Used Queue

LeetCode 432 - All O`one Data Structure

LeetCode 430 - Flatten a Multilevel Doubly Linked List

LeetCode 716 - Max Stack

LeetCode 146 - LRU Cache

LeetCode 1670 - Design Front Middle Back Queue

LeetCode 432: All O'one Data Structure

LeetCode 430: Flatten a Multilevel Doubly Linked List