- 1. Two Sum - 3 approaches: 2HeadSearch, HashSet
- 170. Two Sum III - Data Structure Design - 1 approach: 2HeadScan
- 653. Two Sum IV - Input is a BST - 1 approach: TreeTraverse, 2HeadScan
- 206. Reverse Linked List - 2 approaches: Iterative/Recursive+LinkedList
- 21. Merge 2 Sorted List - 2 approaches: Iterative/Recursive+LinkedList
- 374. Guess Number Higher or Lower - 2 approaches: BinarySearch, TernarySearch
- 121. Best Time to Buy and Sell Stock - 1 approach: 2HeadScan
- 122. Best Time to Buy and Sell Stock II - 1 appraoch: 2HeadScan
- 53. Maximum Subarray - 1 approach: 2HeadScan
- 252. Meeting Rooms - 1 approach: Sorting
- 258. Add Digits - 2 approach: ForLoop, Math
- 997. Find the Town Judge - 1 approach: StartLikeGraph
- 929. Unique Email Addresses - 1 approach: Sorting
- 288. Unique Word Abbreviation - 1 approach: HashMap
- 320. Generalized Abbrevation - 2 approaches: Backtrack, BitManipulation
- 78. Subsets - 3 approaches: Backtrack, BitManipulation, DFS
- 90. Subsets II - 2 approach: Backtrack, DFS
- 15. 3Sum - 1 approach: 2HeadSearch
- 18. 4Sum - 1 approach: 2HeadSearch
- 92. Reverse Linked List II - 2 approaches: Iterative/Recursive+LinkedList
- 2. Add Two Numbers - 1 approach: BigNumber+LinkedList
- 445. Add Two Numbers II - 2 approaches: Stack, Backtrack+LinkedList
- 5. Longest Palindromic String - 1 approach: DP
- 338. Counting Bits - 2 approaches: BasicMath, DP
- 207. Course Schedule - 3 approaches: TopologicalSort, DFS+CycleDetection
- 210. Course Schedule II - 3 approaches: TopologicalSort/DFS, DFS+Stack
- 138. Copy List with Random Pointer - 1 approach: DFS+LinkedList
- 200. Number of Islands - 3 approaches: FindConnectedComponents by DFS/BFS/UnionFind
- 322. Coin Change - 1 approach: DP
- 64. Minimum Path Sum - 2 approach: DP+BFS
- 62. Unique Paths - 1 approach: DP
- 63. Unique Paths II - 1 approach: DP
- 253. Meeting Rooms II - 1 approach: Sorting+HashSet
- 904. Fruits into Baskets - 1 approach: 2HeadSearch
- 31. Next Permutation - 1 approach: Swap
- 46. Permutations - 1 approach: DFS
- 47. Permutations II - 1 approach: DFS+HashMap
- 39. Combination Sum - 1 approach: DFS
- 77. Combinations - 1 approach: DFS
- 40. Combination Sum II - 1 approach: DFS
- 60. Permutation Sequence - 1 approach: DFS
- 267. Palidrome Permutations II - 1 approach: DFS+Cut
- 8. String to Integer (atoi) - 1 approach: Simulation
- 6. ZigZag Conversion - 1 approach: Math
- 247. Strobogrammatic Number II - 1 approach: DFS
- 153. Find Minimum in Rotated Sorted Array - 2 approach: ForLoop, BinarySearch
- 56. Merge Intervals - 1 approach: Sort+Stack
- 694. Number of Distinct Islands - 1 approach: DFS+Sorting
- 254. Factor Combinations - 1 approach: DFS
- 560. Subarray Sum Equals K - 1 approach: HashMap
- 139. Word Break - 1 approach: DFS+DP
- 323. Number of Connected Components in Undirected Graph - 1 approach: DFS
- 785. Is Graph Bipartite - 1 approach: DFS
- 698. Partition to K Equal Sum Sets - 1 approach: DFS
- 973. K Closest Points to Origin - 2 approach: Sort,Partition
- 983. Minimum Cost For Tickets - 1 approach: DP
- 721. Accounts Merge - 1 attempt: DFS
- 971. Flip Binary Tree To Match Preorder Traversal - 1 approach: DFS
- 285. Inorder Successor in BST - 1 approach: DFS
- 449. Serialize and Deserialize BST - 1 approach: TreeTraversal
- 11. Container With Most Water - 1 approach: 2HeadSearch
- 411. Minimum Unique Word Abbreviation - 1 approach: Backtrack+Pruning
- 146. LRU Cache - 1 approach: LinkedList+HashMap
- 4. Median of Two Sorted Arrays - 1 approach: BinarySearch
- 42. Trapping the Water - 1 approach: Math
- 301. Remove Invalid Parentheses - 1 approach: DFS
- 23. Merge K Sorted Lists - 2 approaches: Merge, Divide&Conquer
- 140. Word Break II - 1 approach: DFS+DP
- 273. Integer to English Words - 1 approach: Brute-Force
- 269. Alien Dictionary - 1 approach: DFS+TopologicalSort
- 329. Longest Increasing Path in a Matrix - 1 solution: DFS+DP
- 472. Concatenated Words - 1 approach: DFS
- 488. Zuma Game - 1 approach: DFS
- 428. Serialize and Deserialize N-ary Tree - 1 approach: TreeTraversal
- 924. Minimize Malware Spread - 1 approach: DFS
- 745. Prefix and Suffix Search - 1 attempt: Trie
- 100. 3N+1 Problem
- 246. 10 20 30
- 816. Abbott's Revenge
- 1003. OTAKU
- 3100. Goldback Conjecture
- 3101. Primed Subsequence
- 3102. Hangover
- 3103. Humidex
- 3104. Ugly Numbers
- 3105. Self Numbers
- 3106. Summation of Four Primes
- 3107. Digit Primes
- 3108. Prime Gap
- 3109. Adding Reversed Numbers
- 3110. Blue Jeans
- 3111 Oulipo
- 3112. Very Easy !!!
- 3113. Exponentiation
- 3114. If We Were a Child Again, simpler solution
- 3116. Power Strings, faster solution
- 3117. Period
- 3118. Seek the Name Seek the Fame
- 3130. Find them Catch them
- 3131. Cube Stacking
- 3181. Pass Muraille
- 3182. Tian Ji The Horse Racing
- 3183. Wooden Sticks
- 3184. Copying Books
- 3186. Brackets sequence
- 3187. Dollars
- 3188. Longest Match
- 3189. History Grading
- 3190. Skiing
- 3191. Wavio Sequence
- 3193. Interleaved Periodic String
- 3197. Visible Lattice, faster solution
- 3199. Find The Number, another solution
- 3212. The Hardest Problem Ever
- 3214. The Game
- 3215. Packets
- 3226. John's trip
- 3231. Nearest Common Ancestors, simpler solution
- 3232. Fence Repair
- 3243. Constructing Roads
- 3244. Agri Net
- 3245. ID Codes
- 3246. Generate Fast
- 3247. Combinations
- 3248. Game of Connections
- 3310. Airplane Parking
- 3319. Nowhere Money
- 3375. Factstone Benchmark
- 3376. Bridge
- 3377. Matches Game
- 3386. How Many Ones Needed, another solution
- 3486. Ping pong
- 3487. Timer
- 3513. Farey Sequence
- 3517. Collision Detection
- 3531. Stop Growing
- 3534. Knots
- 7315. Frogger
- 7423. Binomial Showdown
- 7432. Error Correction
- 7501. Ants
- 10125. Sumsets
- 10537. Toll! Revisited
- 10608. Visit
- 12639. Hexagonal Puzzle
- Qualification Round: QR