| Two Sum ↗ | Easy | Array, Hash Table | |
| Merge Intervals ↗ | Medium | Array, Sorting | |
| Best Time to Buy and Sell Stock ↗ | Easy | Array, Dynamic Programming | |
| Longest Substring Without Repeating Characters ↗ | Medium | Hash Table, String, Sliding Window | |
| Valid Parentheses ↗ | Easy | String, Stack | |
| Insert Delete GetRandom O(1) ↗ | Medium | Array, Hash Table, Math | |
| Add Two Numbers ↗ | Medium | Linked List, Math, Recursion | |
| Longest Palindromic Substring ↗ | Medium | Two Pointers, String, Dynamic Programming | |
| Number of Islands ↗ | Medium | Array, Depth-First Search, Breadth-First Search | |
| Decode String ↗ | Medium | String, Stack, Recursion | |
| Word Search ↗ | Medium | Array, String, Backtracking | |
| Flatten a Multilevel Doubly Linked List ↗ | Medium | Linked List, Depth-First Search, Doubly-Linked List | |
| Trapping Rain Water ↗ | Hard | Array, Two Pointers, Dynamic Programming | |
| Subarray Sum Equals K ↗ | Medium | Array, Hash Table, Prefix Sum | |
| Group Anagrams ↗ | Medium | Array, Hash Table, String | |
| Meeting Rooms II ↗ | Medium | Array, Two Pointers, Greedy | |
| Median of Two Sorted Arrays ↗ | Hard | Array, Binary Search, Divide and Conquer | |
| Container With Most Water ↗ | Medium | Array, Two Pointers, Greedy | |
| Evaluate Division ↗ | Medium | Array, String, Depth-First Search | |
| Majority Element ↗ | Easy | Array, Hash Table, Divide and Conquer | |
| Longest Repeating Character Replacement ↗ | Medium | Hash Table, String, Sliding Window | |
| 3Sum ↗ | Medium | Array, Two Pointers, Sorting | |
| Longest Consecutive Sequence ↗ | Medium | Array, Hash Table, Union-Find | |
| Roman to Integer ↗ | Easy | Hash Table, Math, String | |
| Merge Two Sorted Lists ↗ | Easy | Linked List, Recursion | |
| Move Zeroes ↗ | Easy | Array, Two Pointers | |
| Climbing Stairs ↗ | Easy | Math, Dynamic Programming, Memoization | |
| Coin Change ↗ | Medium | Array, Dynamic Programming, Breadth-First Search | |
| Invalid Transactions ↗ | Medium | Array, Hash Table, String | |
| Word Break II ↗ | Hard | Array, Hash Table, String | |
| Merge Sorted Array ↗ | Easy | Array, Two Pointers, Sorting | |
| Valid Anagram ↗ | Easy | Hash Table, String, Sorting | |
| Rotate Image ↗ | Medium | Array, Math, Matrix | |
| Remove Duplicates from Sorted Array ↗ | Easy | Array, Two Pointers | |
| Search in Rotated Sorted Array ↗ | Medium | Array, Binary Search | |
| Generate Parentheses ↗ | Medium | String, Dynamic Programming, Backtracking | |
| Remove Element ↗ | Easy | Array, Two Pointers | |
| Single Number ↗ | Easy | Array, Bit Manipulation | |
| Rotting Oranges ↗ | Medium | Array, Breadth-First Search, Matrix | |
| Longest Common Prefix ↗ | Easy | Array, String, Trie | |