| 1 | Two Sum | Easy |
| 3 | Longest Substring Without Repeating Characters | Medium |
| 18 | 4Sum | Medium |
| 30 | Substring with Concatenation of All Words | Hard |
| 36 | Valid Sudoku | Medium |
| 37 | Sudoku Solver | Hard |
| 49 | Group Anagrams | Medium |
| 76 | Minimum Window Substring | Hard |
| 85 | Maximal Rectangle | Hard |
| 94 | Binary Tree Inorder Traversal | Medium |
| 136 | Single Number | Easy |
| 138 | Copy List with Random Pointer | Medium |
| 149 | Max Points on a Line | Hard |
| 166 | Fraction to Recurring Decimal | Medium |
| 187 | Repeated DNA Sequences | Medium |
| 202 | Happy Number | Easy |
| 229 | Majority Element II | Medium |
| 242 | Valid Anagram | Easy |
| 268 | Missing Number | Easy |
| 380 | Insert Delete GetRandom O(1) | Medium |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | Hard |
| 387 | First Unique Character in a String | Easy |
| 389 | Find the Difference | Easy |
| 454 | 4Sum II | Medium |
| 496 | Next Greater Element I | Easy |
| 525 | Contiguous Array | Medium |
| 560 | Subarray Sum Equals K | Medium |
| 645 | Set Mismatch | Easy |
| 697 | Degree of an Array | Easy |
| 706 | Design HashMap | Easy |