LeetCode

LeetCode/LintCode/HackerRank solutions in Java 8 / JavaScript.

*: LintCode | **: HackerRank | ***: GeeksforGeeks

Topics

• Array
• String
• Binary Tree
• Binary Search
• Linked List
• HashMap
• Queue
• Heap
• Two Pointers
• Math
• Breadth-First Search
• Depth-First Search
• Backgtracking
• Stack
• Dynamic Programming
• Sort
• Recursion
• Graph

Title	Solution	Difficulty
001. Two Sum	Solution	Easy
003. Longest Substring Without Repeating Characters	Solution	Medium
005. Longest Palindromic Substring	Solution	Medium
007. Reverse Integer	Solution	Easy
012. Integer to Roman	Solution	Medium
013. Roman to Integer	Solution	Easy
014. Longest Common Prefix	Solution	Easy
015. 3Sum	Solution	Medium
017. Letter Combinations of a Phone Number	Solution	Medium
019. Remove Nth Node From End of List	Solution	Medium
021. Merge Two Sorted Lists	Solution	Easy
022. Generate Parentheses	Solution	Medium
028. Implement_strStr()	Solution	Easy
031. Next Permutation	Solution	Medium
035. Search Insert Position	Solution	Easy
043. Multiply Strings	Solution	Medium
049. Group Anagrams	Solution	Medium
055. Jump Game	Solution	Medium
062. Unique Paths	Solution	Medium
067. Add Binary	Solution	Easy
070. Climbing Stairs	Solution	Easy
078. Subsets	Solution	Medium
088. Merge Sorted Array	Solution	Easy
094. Binary Tree Inorder Traversal	Solution	Medium
102. Binary Tree Level Order Traversal	Solution	Medium
133. Clone Graph	Solution	Medium
139. Word Break	Solution	Medium
144. Binary Tree Preorder Traversal	Solution	Medium
151. Reverse Words in a String	Solution	Medium
155. Min Stack	Solution	Easy
168. Excel Sheet Column Title	Solution	Easy
200. Number of Islands	Solution	Medium
209. Minimum Size Subarray Sum	Solution	Medium
206. Reverse Linked List	Java/JS	Easy
227. Basic Calculator II	Java/JS	Medium
277. Find the Celebrity	Java/JS	Medium
273. Integer to English Words	Solution	Hard
344. Reverse String	Java/JS	Easy
347. Top K Frequent Elements	Solution	Medium
441. Arranging Coins	Solution	Easy
443. String Compression	Solution	Medium
557. Reverse Words in a String III	Solution	Easy
657. Judge Route Circle	Solution	Easy
692. Top K Frequent Words	Solution	Medium
772. Basic Calculator III	Solution	Hard
*109. Triangle	Solution	Easy
**Count Duplicates	Solution	Easy
**Implement Stack By LinkedList	Solution	Easy
**Delete Node Greater than X	Solution	Easy
**Merge in Between.java	Solution	Easy
**Expression_Token	Solution	Easy
**Build Subsequences	Solution	Easy
**Merge in Between	Solution	Medium
**Missing Words	Solution	Easy
***Check_Binary_String.java	Solution	Easy

Array

Title	Solution	Difficulty
001. Two Sum	Solution	Easy
015. 3Sum	Solution	Medium
035. Search Insert Position	Solution	Easy
078. Subsets	Solution	Medium
031. Next Permutation	Solution	Medium
227. Find the Celebrity	Solution	Medium
088. Merge Sorted Array	Solution	Easy
209. Minimum Size Subarray Sum	Solution	Medium
**Count Duplicates	Solution	Easy

String

Title	Solution	Difficulty
003. Longest Substring Without Repeating Characters	Solution	Medium
005. Longest Palindromic Substring	Solution	Medium
012. Integer to Roman	Solution	Medium
013. Roman to Integer	Solution	Easy
014. Longest Common Prefix	Solution	Easy
017. Letter Combinations of a Phone Number	Solution	Medium
022. Generate Parentheses	Solution	Medium
049. Group Anagrams	Solution	Medium
227. Basic Calculator II	Solution	Medium
772. Basic Calculator III	Solution	Hard
443. String Compression	Solution	Medium
028. Implement_strStr()	Solution	Easy
043. Multiply Strings	Solution	Medium
067. Add Binary	Solution	Easy
151. Reverse Words in a String	Solution	Medium
273. Integer to English Words	Solution	Hard
344. Reverse String	Solution	Easy
557. Reverse Words in a String III	Solution	Easy
657. Judge Route Circle	Solution	Easy
**Expression_Token	Solution	Easy
**Build Subsequences	Solution	Easy
**Merge in Between	Solution	Medium
**Missing Words	Solution	Easy

Binary Tree

Title	Solution	Difficulty
094. Binary Tree Inorder Traversal	Solution	Medium
102. Binary Tree Level Order Traversal	Solution	Medium
144. Binary Tree Preorder Traversal	Solution	Medium

Binary Search

Title	Solution	Difficulty
035. Search Insert Position	Solution	Easy

Linked List

Title	Solution	Difficulty
19. Remove Nth Node From End of List	Solution	Medium
021. Merge Two Sorted Lists	Solution	Easy
206. Reverse Linked List	Solution	Easy
**Delete Node Greater than X	Solution	Easy
**Merge in Between.java	Solution	Easy

HashMap

Title	Solution	Difficulty
003. Longest Substring Without Repeating Characters	Solution	Medium
049. Group Anagrams	Solution	Medium
347. Top K Frequent Elements	Solution	Medium
692. Top K Frequent Words	Solution	Medium

Queue

Title	Solution	Difficulty
102. Binary Tree Level Order Traversal	Solution	Medium

Heap

Title	Solution	Difficulty
347. Top K Frequent Elements	Solution	Medium
692. Top K Frequent Words	Solution	Medium

Two Pointers

Title	Solution	Difficulty
003. Longest Substring Without Repeating Characters	Solution	Medium
031. Next Permutation	Solution	Medium
088. Merge Sorted Array	Solution	Easy

Math

Title	Solution	Difficulty
007. Reverse Integer	Solution	Easy
012. Integer to Roman	Solution	Medium
013. Roman to Integer	Solution	Easy
168. Excel Sheet Column Title	Solution	Easy
273. Integer to English Words	Solution	Hard
441. Arranging Coins	Solution	Easy

Breadth-First Search

Title	Solution	Difficulty
200. Number of Islands	Solution	Medium

Depth-First Search

Title	Solution	Difficulty

Backgtracking

Title	Solution	Difficulty
017. Letter Combinations of a Phone Number	Solution	Medium
022. Generate Parentheses	Solution	Medium

Stack

Title	Solution	Difficulty
094. Binary Tree Inorder Traversal	Solution	Medium
144. Binary Tree Preorder Traversal	Solution	Medium
155. Min Stack	Solution	Easy
**Implement Stack By LinkedList	Solution	Easy

Dynamic Programming

Title	Solution	Difficulty
005. Longest Palindromic Substring	Solution	Medium
062. Unique Paths	Solution	Medium
070. Climbing Stairs	Solution	Easy
055. Jump Game	Solution	Medium
139. Word Break	Solution	Medium
*109. Triangle	Solution	Easy

Sort

Title	Solution	Difficulty
049. Group Anagrams	Solution	Medium

Recursion

Title	Solution	Difficulty

Graph

Title	Solution	Difficulty
133. Clone Graph	Solution	Medium