| 4. Median of Two Sorted Arrays | | | Solve | Hard | | |
| 10. Regular Expression Matching | | | Solve | Hard | | |
| 23. Merge k Sorted Lists | | | Solve | Hard | | |
| 25. Reverse Nodes in k-Group | | | Solve | Hard | | |
| 30. Substring with Concatenation of All Words | | | Solve | Hard | | |
| 32. Longest Valid Parentheses | | | Solve | Hard | | |
| 37. Sudoku Solver | | | Solve | Hard | | |
| 41. First Missing Positive | | | Solve | Hard | | |
| 42. Trapping Rain Water | | | Solve | Hard | | |
| 44. Wildcard Matching | | | Solve | Hard | | |
| 51. N-Queens | | | Solve | Hard | | |
| 68. Text Justification | | | Solve | Hard | | |
| 76. Minimum Window Substring | | | Solve | Hard | | |
| 84. Largest Rectangle in Histogram | | | Solve | Hard | | |
| 124. Binary Tree Maximum Path Sum | | | Solve | Hard | | |
| 126. Word Ladder II | | | Solve | Hard | | |
| 127. Word Ladder | | | Solve | Hard | | |
| 135. Candy | | | Solve | Hard | | |
| 140. Word Break II | | | Solve | Hard | | |
| 158. Read N Characters Given read4 II - Call Multiple Times | | | Solve | Hard | | |
| 185. Department Top Three Salaries | | | Solve | Hard | | |
| 212. Word Search II | | | Solve | Hard | | |
| 214. Shortest Palindrome | | | Solve | Hard | | |
| 218. The Skyline Problem | | | Solve | Hard | | |
| 224. Basic Calculator | | | Solve | Hard | | |
| 233. Number of Digit One | | | Solve | Hard | | |
| 239. Sliding Window Maximum | | | Solve | Hard | | |
| 269. Alien Dictionary | | | Solve | Hard | | |
| 273. Integer to English Words | | | Solve | Hard | | |
| 295. Find Median from Data Stream | | | Solve | Hard | | |
| 297. Serialize and Deserialize Binary Tree | | | Solve | Hard | | |
| 312. Burst Balloons | | | Solve | Hard | | |
| 315. Count of Smaller Numbers After Self | | | Solve | Hard | | |
| 317. Shortest Distance from All Buildings | | | Solve | Hard | | |
| 329. Longest Increasing Path in a Matrix | | | Solve | Hard | | |
| 336. Palindrome Pairs | | | Solve | Hard | | |
| 352. Data Stream as Disjoint Intervals | | | Solve | Hard | | |
| 358. Rearrange String k Distance Apart | | | Solve | Hard | | |
| 403. Frog Jump | | | Solve | Hard | | |
| 428. Serialize and Deserialize N-ary Tree | | | Solve | Hard | | |
| 460. LFU Cache | | | Solve | Hard | | |
| 472. Concatenated Words | | | Solve | Hard | | |
| 480. Sliding Window Median | | | Solve | Hard | | |
| 483. Smallest Good Base | | | Solve | Hard | | |
| 489. Robot Room Cleaner | | | Solve | Hard | | |
| 517. Super Washing Machines | | | Solve | Hard | | |
| 568. Maximum Vacation Days | | | Solve | Hard | | |
| 588. Design In-Memory File System | | | Solve | Hard | | |
| 639. Decode Ways II | | | Solve | Hard | | |
| 642. Design Search Autocomplete System | | | Solve | Hard | | |