| 201. Bitwise AND of Numbers Range | Solution | Solve | Medium | | |
| 202. Happy Number | Solution | Solve | Easy | | |
| 203. Remove Linked List Elements | Solution | Solve | Easy | | |
| 204. Count Primes | Solution | Solve | Medium | | |
| 205. Isomorphic Strings | Solution | Solve | Easy | | |
| 206. Reverse Linked List | Solution | Solve | Easy | | |
| 207. Course Schedule | Solution | Solve | Medium | | |
| 208. Implement Trie (Prefix Tree) | Solution | Solve | Medium | | |
| 209. Minimum Size Subarray Sum | Solution | Solve | Medium | | |
| 210. Course Schedule II | Solution | Solve | Medium | | |
| 211. Design Add and Search Words Data Structure | Solution | Solve | Medium | | |
| 212. Word Search II | Solution | Solve | Hard | | |
| 213. House Robber II | Solution | Solve | Medium | | |
| 214. Shortest Palindrome | Solution | Solve | Hard | | |
| 215. Kth Largest Element in an Array | Solution | Solve | Medium | | |
| 216. Combination Sum III | Solution | Solve | Medium | | |
| 217. Contains Duplicate | Solution | Solve | Easy | | |
| 218. The Skyline Problem | Solution | Solve | Hard | | |
| 219. Contains Duplicate II | Solution | Solve | Easy | | |
| 220. Contains Duplicate III | Solution | Solve | Hard | | |
| 221. Maximal Square | Solution | Solve | Medium | | |
| 222. Count Complete Tree Nodes | Solution | Solve | Medium | | |
| 223. Rectangle Area | Solution | Solve | Medium | | |
| 224. Basic Calculator | Solution | Solve | Hard | | |
| 225. Implement Stack using Queues | Solution | Solve | Easy | | |
| 226. Invert Binary Tree | Solution | Solve | Easy | | |
| 227. Basic Calculator II | Solution | Solve | Medium | | |
| 228. Summary Ranges | Solution | Solve | Easy | | |
| 229. Majority Element II | Solution | Solve | Medium | | |
| 230. Kth Smallest Element in a BST | Solution | Solve | Medium | | |
| 231. Power of Two | Solution | Solve | Easy | | |
| 232. Implement Queue using Stacks | Solution | Solve | Easy | | |
| 233. Number of Digit One | Solution | Solve | Hard | | |
| 234. Palindrome Linked List | Solution | Solve | Easy | | |
| 235. Lowest Common Ancestor of a Binary Search Tree | Solution | Solve | Medium | | |
| 236. Lowest Common Ancestor of a Binary Tree | Solution | Solve | Medium | | |
| 237. Delete Node in a Linked List | Solution | Solve | Medium | | |
| 238. Product of Array Except Self | Solution | Solve | Medium | | |
| 239. Sliding Window Maximum | Solution | Solve | Hard | | |
| 240. Search a 2D Matrix II | Solution | Solve | Medium | | |
| 241. Different Ways to Add Parentheses | Solution | Solve | Medium | | |
| 242. Valid Anagram | Solution | Solve | Easy | | |
| 243. Shortest Word Distance | Solution | Solve | Easy | | |
| 244. Shortest Word Distance II | Solution | Solve | Medium | | |
| 245. Shortest Word Distance III | Solution | Solve | Medium | | |
| 246. Strobogrammatic Number | Solution | Solve | Easy | | |
| 247. Strobogrammatic Number II | Solution | Solve | Medium | | |
| 248. Strobogrammatic Number III | Solution | Solve | Hard | - | |
| 249. Group Shifted Strings | Solution | Solve | Medium | | |
| 250. Count Univalue Subtrees | Solution | Solve | Medium | | |
