| 140 | Word Break II | Hard |
| 145 | Binary Tree Postorder Traversal | Hard |
| 146 | LRU Cache | Hard |
| 149 | Max Points on a Line | Hard |
| 154 | Find Minimum in Rotated Sorted Array II | Hard |
| 164 | Maximum Gap | Hard |
| 174 | Dungeon Game | Hard |
| 224 | Basic Calculator | Hard |
| 239 | Sliding Window Maximum | Hard |
| 295 | Find Median from Data Stream | Hard |
| 315 | Count of Smaller Numbers After Self | Hard |
| 316 | Remove Duplicate Letters | Hard |
| 332 | Reconstruct Itinerary | Hard |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | Hard |
| 403 | Frog Jump | Hard |
| 458 | Poor Pigs | Hard |
| 514 | Freedom Trail | Hard |
| 815 | Bus Routes | Hard |
| 823 | Split Array With Same Average | Hard |
| 920 | Number of Music Playlists | Hard |
| 980 | Unique Paths III | Hard |
| 1074 | Number of Submatrices That Sum to Target | Hard |
| 1092 | Shortest Common Supersequence | Hard |
| 1095 | Find in Mountain Array | Hard |
| 1220 | Count Vowels Permutation | Hard |
| 1235 | Maximum Profit in Job Scheduling | Hard |
| 1269 | Number of Ways to Stay in the Same Place After Some Steps | Hard |
| 1289 | Minimum Falling Path Sum II | Hard |
| 1335 | Minimum Difficulty of a Job Schedule | Hard |
| 1359 | Count All Valid Pickup and Delivery Options | Hard |