| 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 |
| 204 | Count Primes | Medium |
| 205 | Isomorphic Strings | Easy |
| 219 | Contains Duplicate II | Easy |
| 229 | Majority Element II | Medium |
| 242 | Valid Anagram | Easy |
| 268 | Missing Number | Easy |
| 290 | Word Pattern | Easy |
| 299 | Bulls and Cows | Medium |
| 336 | Palindrome Pairs | Hard |
| 347 | Top K Frequent Elements | Medium |
| 349 | Intersection of Two Arrays | Easy |
| 350 | Intersection of Two Arrays II | Easy |
| 355 | Design Twitter | Medium |
| 380 | Insert Delete GetRandom O(1) | Medium |