201 
Bitwise AND of Numbers Range 
Medium 

202 
Happy Number 
Easy 

203 
Remove Linked List Elements 
Easy 

204 
Count Primes 
Easy 

205 
Isomorphic Strings 
Easy 

206 
Reverse Linked List 
Easy 
Linked List

207 
Course Schedule 
Medium 

208 
Implement Trie (Prefix Tree) 
Medium 

209 
Minimum Size Subarray Sum 
Medium 

210 
Course Schedule II 
Medium 

211 
Design Add and Search Words Data Structure 
Medium 

212 
Word Search II 
Hard 

213 
House Robber II 
Medium 

214 
Shortest Palindrome 
Hard 

215 
Kth Largest Element in an Array 
Medium 

216 
Combination Sum III 
Medium 

217 
Contains Duplicate 
Easy 

218 
The Skyline Problem 
Hard 

219 
Contains Duplicate II 
Easy 

220 
Contains Duplicate III 
Medium 

221 
Maximal Square 
Medium 

222 
Count Complete Tree Nodes 
Medium 
Binary Search

Tree

223 
Rectangle Area 
Medium 

224 
Basic Calculator 
Hard 

225 
Implement Stack using Queues 
Easy 

226 
Invert Binary Tree 
Easy 
Tree

227 
Basic Calculator II 
Medium 

228 
Summary Ranges 
Easy 

229 
Majority Element II 
Medium 

230 
Kth Smallest Element in a BST 
Medium 
Binary Search

Tree

231 
Power of Two 
Easy 

232 
Implement Queue using Stacks 
Easy 

233 
Number of Digit One 
Hard 

234 
Palindrome Linked List 
Easy 

235 
Lowest Common Ancestor of a Binary Search Tree 
Easy 
Tree

236 
Lowest Common Ancestor of a Binary Tree 
Medium 
Tree

237 
Delete Node in a Linked List 
Easy 

238 
Product of Array Except Self 
Medium 

239 
Sliding Window Maximum 
Hard 

240 
Search a 2D Matrix II 
Medium 

241 
Different Ways to Add Parentheses 
Medium 

242 
Valid Anagram 
Easy 

250 
Count Univalue Subtrees 
Medium 
Tree

255 
Verify Preorder Sequence in Binary Search Tree 
Medium 
Stack 
Tree

257 
Binary Tree Paths 
Easy 
Tree

Depthfirst Search

258 
Add Digits 
Easy 

260 
Single Number III 
Medium 

261 
Graph Valid Tree 
Medium 

263 
Ugly Number 
Easy 

264 
Ugly Number II 
Medium 

268 
Missing Number 
Easy 

269 
Alien Dictionary 
Hard 

270 
Closest Binary Search Tree Value 
Easy 
Binary Search

Tree

272 
Closest Binary Search Tree Value II 
Hard 
Stack 
Tree

273 
Integer to English Words 
Hard 

274 
HIndex 
Medium 

275 
HIndex II 
Medium 

278 
First Bad Version 
Easy 

279 
Perfect Squares 
Medium 

282 
Expression Add Operators 
Hard 

283 
Move Zeroes 
Easy 

284 
Peeking Iterator 
Medium 

285 
Inorder Successor in BST 
Medium 
Tree

287 
Find the Duplicate Number 
Medium 

289 
Game of Life 
Medium 

290 
Word Pattern 
Easy 

292 
Nim Game 
Easy 

295 
Find Median from Data Stream 
Hard 

297 
Serialize and Deserialize Binary Tree 
Hard 
Tree

Design

298 
Binary Tree Longest Consecutive Sequence 
Medium 
Tree

299 
Bulls and Cows 
Medium 

300 
Longest Increasing Subsequence 
Medium 
