Introduction

Complete solutions to Leetcode problems, updated daily.

Solution List

Easy

#	Title	Tags
0001	Two Sum	Array, Hash Table
0007	Reverse Integer	Math
0009	Palindrome Number	Math
0013	Roman to Integer	Math, String
0014	Longest Common Prefix	String
0020	Valid Parentheses	String, Stack
0021	Merge Two Sorted Lists	Linked List
0028	Implement strStr()	Two Pointers, String
0035	Search Insert Position	Array, Binary Search
0053	Maximum Subarray	Array, Divide and Conquer, Dynamic Programming
0070	Climbing Stairs	Dynamic Programming
0083	Remove Duplicates from Sorted List	Linked List
0136	Single Number	Hash Table, Bit Manipulation
0141	Linked List Cycle	Linked List, Two Pointers
0155	Min Stack	Stack, Design
0175	Combine Two Tables	SQL
0176	Second Highest Salary	SQL
0181	Employees Earning More Than Their Managers	SQL
0182	Duplicate Emails	SQL
0183	Customers Who Never Order	SQL
0189	Rotate Array	Array
0196	Delete Duplicate Emails	SQL
0197	Rising Temperature	SQL
0198	House Robber	Dynamic Programming
0203	Remove Linked List Elements	Linked List
0231	Power of Two	Math, Bit Manipulation
0234	Palindrome Linked List	Linked List, Two Pointers
0235	Lowest Common Ancestor of a Binary Search Tree	Tree
0237	Delete Node in a Linked List	Linked List
0344	Reverse String	Two Pointers, String
0581	Shortest Unsorted Continuous Subarray	Array
0595	Big Countries	SQL
0596	Classes More Than 5 Students	SQL
0605	Can Place Flowers	Array
0620	Not Boring Movies	SQL
0627	Swap Salary	SQL
0695	Max Area of Island	Array, Depth-first Search
0703	Kth Largest Element in a Stream	Heap
0707	Design Linked List	Linked List, Design
0876	Middle of the Linked List	Linked List

Medium

#	Title	Tags
0002	Add Two Numbers	Linked List, Math
0003	Longest Substring Without Repeating Characters	Hash Table, Two Pointers, String
0005	Longest Palindromic Substring	String, Dynamic Programming
0015	3Sum	Array, Two Pointers
0018	4Sum	Array, Hash Table, Two Pointers
0019	Remove Nth Node From End of List	Linked List, Two Pointers
0024	Swap Nodes in Pairs	Linked List
0031	Next Permutation	Array
0046	Permutations	Backtracking
0047	Permutations II	Backtracking
0054	Spiral Matrix	Array
0059	Spiral Matrix II	Array
0061	Rotate List	Linked List, Two Pointers
0062	Unique Paths	Array, Dynamic Programming
0063	Unique Paths II	Array, Dynamic Programming
0075	Sort Colors	Array, Two Pointers, Sort
0082	Remove Duplicates from Sorted List II	Linked List
0086	Partition List	Linked List, Two Pointers
0092	Reverse Linked List II	Linked List
0094	Binary Tree Inorder Traversal	Hash Table, Stack, Tree
0096	Unique Binary Search Trees	Tree, Dynamic Programming
0102	Binary Tree Level Order Traversal	Tree, Breadth-first Search
0105	Construct Binary Tree from Preorder and Inorder Traversal	Array, Tree, Depth-first Search
0106	Construct Binary Tree from Inorder and Postorder Traversal	Array, Tree, Depth-first Search
0127	Word Ladder	Breadth-first Search
0130	Surrounded Regions	Depth-first Search, Breadth-first Search, Union Find
0137	Single Number II	Bit Manipulation
0138	Copy List with Random Pointer	Hash Table, Linked List
0142	Linked List Cycle II	Linked List, Two Pointers
0143	Reorder List	Linked List
0144	Binary Tree Preorder Traversal	Stack, Tree
0150	Evaluate Reverse Polish Notation	Stack
0153	Find Minimum in Rotated Sorted Array	Array, Binary Search
0177	Nth Highest Salary	SQL
0178	Rank Scores	SQL
0180	Consecutive Numbers	SQL
0184	Department Highest Salary	SQL
0300	Longest Increasing Subsequence	Binary Search, Dynamic Programming
0328	Odd Even Linked List	Linked List
0343	Integer Break	Math, Dynamic Programming
0817	Linked List Components	Linked List
0938	Range Sum of BST	Binary Search Tree

Hard

#	Title	Tags
0004	Median of Two Sorted Arrays	Array, Binary Search, Divide and Conquer
0023	Merge k Sorted Lists	Linked List, Divide and Conquer, Heap
0032	Longest Valid Parentheses	String, Dynamic Programming
0084	Largest Rectangle in Histogram	Array, Stack
0145	Binary Tree Postorder Traversal	Stack, Tree
0295	Find Median from Data Stream	Heap, Design
0312	Burst Balloons	Divide and Conquer, Dynamic Programming

Contributions

I'm looking for long-term contributors/partners to this repo! Send me PRs if you're interested! See the following:

• Fork this repository to your own GitHub account and then clone it to your local device.
• Add or update file of the repository, then commit and push it to your GitHub repository.
• Submit a pull request with your changes!
• For more details, see CONTRIBUTING.md

Contributors

" If you want to go fast, go alone. If you want to go far, go together. And that's the spirit of teamwork ".