| 102. Binary Tree Level Order Traversal | | | Solve | Medium | | |
| 103. Binary Tree Zigzag Level Order Traversal | | | Solve | Medium | | |
| 109. Convert Sorted List to Binary Search Tree | | | Solve | Medium | | |
| 113. Path Sum II | | | Solve | Medium | | |
| 114. Flatten Binary Tree to Linked List | | | Solve | Medium | | |
| 116. Populating Next Right Pointers in Each Node | | | Solve | Medium | | |
| 117. Populating Next Right Pointers in Each Node II | | | Solve | Medium | | |
| 122. Best Time to Buy and Sell Stock II | | | Solve | Medium | | |
| 129. Sum Root to Leaf Numbers | | | Solve | Medium | | |
| 131. Palindrome Partitioning | | | Solve | Medium | | |
| 133. Clone Graph | | | Solve | Medium | | |
| 138. Copy List with Random Pointer | | | Solve | Medium | | |
| 139. Word Break | | | Solve | Medium | | |
| 143. Reorder List | | | Solve | Medium | | |
| 146. LRU Cache | | | Solve | Medium | | |
| 148. Sort List | | | Solve | Medium | | |
| 150. Evaluate Reverse Polish Notation | | | Solve | Medium | | |
| 153. Find Minimum in Rotated Sorted Array | | | Solve | Medium | | |
| 155. Min Stack | | | Solve | Medium | | |
| 161. One Edit Distance | | | Solve | Medium | | |
| 162. Find Peak Element | | | Solve | Medium | | |
| 164. Maximum Gap | | | Solve | Medium | | |
| 166. Fraction to Recurring Decimal | | | Solve | Medium | | |
| 173. Binary Search Tree Iterator | | | Solve | Medium | | |
| 179. Largest Number | | | Solve | Medium | | |
| 180. Consecutive Numbers | | | Solve | Medium | | |
| 189. Rotate Array | | | Solve | Medium | | |
| 198. House Robber | | | Solve | Medium | | |
| 199. Binary Tree Right Side View | | | Solve | Medium | | |
| 200. Number of Islands | | | Solve | Medium | | |
| 207. Course Schedule | | | Solve | Medium | | |
| 208. Implement Trie (Prefix Tree) | | | Solve | Medium | | |
| 209. Minimum Size Subarray Sum | | | Solve | Medium | | |
| 210. Course Schedule II | | | Solve | Medium | | |
| 211. Design Add and Search Words Data Structure | | | Solve | Medium | | |
| 215. Kth Largest Element in an Array | | | Solve | Medium | | |
| 227. Basic Calculator II | | | Solve | Medium | | |
| 229. Majority Element II | | | Solve | Medium | | |
| 230. Kth Smallest Element in a BST | | | Solve | Medium | | |
| 235. Lowest Common Ancestor of a Binary Search Tree | | | Solve | Medium | | |
| 236. Lowest Common Ancestor of a Binary Tree | | | Solve | Medium | | |
| 238. Product of Array Except Self | | | Solve | Medium | | |
| 240. Search a 2D Matrix II | | | Solve | Medium | | |
| 247. Strobogrammatic Number II | | | Solve | Medium | | |
| 249. Group Shifted Strings | | | Solve | Medium | | |
| 253. Meeting Rooms II | | | Solve | Medium | | |
| 271. Encode and Decode Strings | | | Solve | Medium | | |
| 274. H-Index | | | Solve | Medium | | |
| 277. Find the Celebrity | | | Solve | Medium | | |
| 285. Inorder Successor in BST | | | Solve | Medium | | |
