1. Two Sum (Solution) 2. Add Two Numbers (Solution) 3. Longest Substring Without Repeating Characters (Solution) 6. ZigZag Conversion (Solution) 7. Reverse Integer (Solution) 8. String to Integer (atoi) (Solution) 9. Palindrome Number (Solution) 10. Regular Expression Matching (Solution) 11. Container With Most Water (Solution) 12. Integer to Roman (Solution) 13. Roman to Integer (Solution) 14. Longest Common Prefix (Solution) 15. 3Sum (Solution) 16. 3Sum Closest (Solution) 17. Letter Combinations of a Phone Number (Solution) 18. 4Sum (Solution) 19. Remove Nth Node From End of List (Solution) 20. Valid Parentheses (Solution) 21. Merge Two Sorted Lists (Solution) 22. Generate Parentheses (Solution) 23. Merge k Sorted Lists (Solution) 24. Swap Nodes in Pairs (Solution) 26. Remove Duplicates from Sorted Array (Solution) 27. Remove Element (Solution) 28. Implement strStr() (Solution) 29. Divide Two Integers (Solution) 31. Next Permutation (Solution) 33. Search in Rotated Sorted Array (Solution) 34. Search for a Range (Solution) 35. Search Insert Position (Solution) 36. Valid Sudoku (Solution) 37. Sudoku Solver (Solution) 38. Count and Say (Solution) 39. Combination Sum (Solution) 40. Combination Sum II (Solution) 42. Trapping Rain Water (Solution) 43. Multiply Strings (Solution) 44. Wildcard Matching (Solution) 46. Permutations (Solution) 47. Permutations II (Solution) 48. Rotate Image (Solution) 49. Group Anagrams (Solution) 50. Pow(x, n) (Solution) 51. N-Queens (Solution) 52. N-Queens II (Solution) 53. Maximum Subarray (Solution) 54. Spiral Matrix (Solution) 55. Jump Game (Solution) 56. Merge Intervals (Solution) 58. Length of Last Word (Solution) 59. Spiral Matrix II (Solution) 60. Permutation Sequence (Solution) 61. Rotate List (Solution) 62. Unique Paths (Solution) 63. Unique Paths II (Solution) 64. Minimum Path Sum (Solution) 66. Plus One (Solution) 67. Add Binary (Solution) 69. Sqrt(x) (Solution) 70. Climbing Stairs (Solution) 71. Simplify Path (Solution) 73. Set Matrix Zeroes (Solution) 74. Search a 2D Matrix (Solution) 75. Sort Colors (Solution) 76. Minimum Window Substring (Solution) 77. Combinations (Solution) 78. Subsets (Solution) 79. Word Search (Solution) 80. Remove Duplicates from Sorted Array II (Solution) 82. Remove Duplicates from Sorted List II (Solution) 83. Remove Duplicates from Sorted List (Solution) 86. Partition List (Solution) 88. Merge Sorted Array (Solution) 89. Gray Code (Solution) 90. Subsets II (Solution) 91. Decode Ways (Solution) 92. Reverse Linked List II (Solution) 93. Restore IP Addresses (Solution) 94. Binary Tree Inorder Traversal (Solution) 95. Unique Binary Search Trees II (Solution) 96. Unique Binary Search Trees (Solution) 98. Validate Binary Search Tree (Solution) 100. Same Tree (Solution) 101. Symmetric Tree (Solution) 102. Binary Tree Level Order Traversal (Solution) 103. Binary Tree Zigzag Level Order Traversal (Solution) 104. Maximum Depth of Binary Tree (Solution) 105. Construct Binary Tree from Preorder and Inorder Traversal (Solution) 106. Construct Binary Tree from Inorder and Postorder Traversal (Solution) 107. Binary Tree Level Order Traversal II (Solution) 108. Convert Sorted Array to Binary Search Tree (Solution) 109. Convert Sorted List to Binary Search Tree (Solution) 110. Balanced Binary Tree (Solution) 111. Minimum Depth of Binary Tree (Solution) 112. Path Sum (Solution) 113. Path Sum II (Solution) 114. Flatten Binary Tree to Linked List (Solution) 116. Populating Next Right Pointers in Each Node (Solution) 117. Populating Next Right Pointers in Each Node II (Solution) 118. Pascal’s Triangle (Solution) 119. Pascal’s Triangle II (Solution) 120. Triangle (Solution) 121. Best Time to Buy and Sell Stock (Solution) 122. Best Time to Buy and Sell Stock II (Solution) 124. Binary Tree Maximum Path Sum (Solution) 125. Valid Palindrome (Solution) 126. Word Ladder II (Solution) 127. Word Ladder (Solution) 129. Sum Root to Leaf Numbers (Solution) 130. Surrounded Regions (Solution) 131. Palindrome Partitioning (Solution) 133. Clone Graph (Solution) 134. Gas Station (Solution) 136. Single Number (Solution) 138. Copy List with Random Pointer (Solution) 139. Word Break (Solution) 140. Word Break II (Solution) 141. Linked List Cycle (Solution) 142. Linked List Cycle II (Solution) 143. Reorder List (Solution) 144. Binary Tree Preorder Traversal (Solution) 145. Binary Tree Postorder Traversal (Solution) 146. LRU Cache (Solution) 147. Insertion Sort List (Solution) 150. Evaluate Reverse Polish Notation (Solution) 151. Reverse Words in a String (Solution) 152. Maximum Product Subarray (Solution) 153. Find Minimum in Rotated Sorted Array (Solution) 155. Min Stack (Solution) 156. Binary Tree Upside Down (Solution) 160. Intersection of Two Linked Lists (Solution) 161. One Edit Distance (Solution) 162. Find Peak Element (Solution) 163. Missing Ranges (Solution) 165. Compare Version Numbers (Solution) 166. Fraction to Recurring Decimal (Solution) 167. Two Sum II - Input array is sorted (Solution) 168. Excel Sheet Column Title (Solution) 169. Majority Element (Solution) 171. Excel Sheet Column Number (Solution) 172. Factorial Trailing Zeroes (Solution) 173. Binary Search Tree Iterator (Solution) 179. Largest Number (Solution) 186. Reverse Words in a String II (Solution) 187. Repeated DNA Sequences (Solution) 189. Rotate Array (Solution) 190. Reverse Bits (Solution) 191. Number of 1 Bits (Solution) 198. House Robber (Solution) 199. Binary Tree Right Side View (Solution) 200. Number of Islands (Solution) 201. Bitwise AND of Numbers Range (Solution) 202. Happy Number (Solution) 203. Remove Linked List Elements (Solution) 204. Count Primes (Solution) 205. Isomorphic Strings (Solution) 206. Reverse Linked List (Solution) 207. Course Schedule (Solution) 208. Implement Trie (Prefix Tree) (Solution) 209. Minimum Size Subarray Sum (Solution) 210. Course Schedule II (Solution) 211. Add and Search Word - Data structure design (Solution) 213. House Robber II (Solution) 215. Kth Largest Element in an Array (Solution) 216. Combination Sum III (Solution) 217. Contains Duplicate (Solution) 219. Contains Duplicate II (Solution) 220. Contains Duplicate III (Solution) 221. Maximal Square (Solution) 222. Count Complete Tree Nodes (Solution) 223. Rectangle Area (Solution) 225. Implement Stack using Queues (Solution) 226. Invert Binary Tree (Solution) 227. Basic Calculator II (Solution) 228. Summary Ranges (Solution) 229. Majority Element II (Solution) 230. Kth Smallest Element in a BST (Solution) 231. Power of Two (Solution) 232. Implement Queue using Stacks (Solution) 234. Palindrome Linked List (Solution) 235. Lowest Common Ancestor of a Binary Search Tree (Solution) 236. Lowest Common Ancestor of a Binary Tree (Solution) 237. Delete Node in a Linked List (Solution) 238. Product of Array Except Self (Solution) 239. Sliding Window Maximum (Solution) 240. Search a 2D Matrix II (Solution) 241. Different Ways to Add Parentheses (Solution) 242. Valid Anagram (Solution) 243. Shortest Word Distance (Solution) 244. Shortest Word Distance II (Solution) 245. Shortest Word Distance III (Solution) 247. Strobogrammatic Number II (Solution) 249. Group Shifted Strings (Solution) 250. Count Univalue Subtrees (Solution) 251. Flatten 2D Vector (Solution) 253. Meeting Rooms II (Solution) 254. Factor Combinations (Solution) 255. Verify Preorder Sequence in Binary Search Tree (Solution) 257. Binary Tree Paths (Solution) 258. Add Digits (Solution) 259. 3Sum Smaller (Solution) 260. Single Number III (Solution) 261. Graph Valid Tree (Solution) 263. Ugly Number (Solution) 264. Ugly Number II (Solution) 266. Palindrome Permutation (Solution) 267. Palindrome Permutation II (Solution) 268. Missing Number (Solution) 271. Encode and Decode Strings (Solution) 274. H-Index (Solution) 275. H-Index II (Solution) 277. Find the Celebrity (Solution) 278. First Bad Version (Solution) 279. Perfect Squares (Solution) 280. Wiggle Sort (Solution) 281. Zigzag Iterator (Solution) 283. Move Zeroes (Solution) 284. Peeking Iterator (Solution) 285. Inorder Successor in BST (Solution) 286. Walls and Gates (Solution) 287. Find the Duplicate Number (Solution) 288. Unique Word Abbreviation (Solution) 289. Game of Life (Solution) 290. Word Pattern (Solution) 291. Word Pattern II (Solution) 292. Nim Game (Solution) 294. Flip Game II (Solution) 295. Find Median from Data Stream (Solution) 297. Serialize and Deserialize Binary Tree (Solution) 298. Binary Tree Longest Consecutive Sequence (Solution) 299. Bulls and Cows (Solution) 300. Longest Increasing Subsequence (Solution) 303. Range Sum Query - Immutable (Solution) 304. Range Sum Query 2D - Immutable (Solution) 306. Additive Number (Solution) 310. Minimum Height Trees (Solution) 311. Sparse Matrix Multiplication (Solution) 313. Super Ugly Number (Solution) 314. Binary Tree Vertical Order Traversal (Solution) 318. Maximum Product of Word Lengths (Solution) 319. Bulb Switcher (Solution) 320. Generalized Abbreviation (Solution) 322. Coin Change (Solution) 323. Number of Connected Components in an Undirected Graph (Solution) 325. Maximum Size Subarray Sum Equals k (Solution) 326. Power of Three (Solution) 328. Odd Even Linked List (Solution) 331. Verify Preorder Serialization of a Binary Tree (Solution) 332. Reconstruct Itinerary (Solution) 333. Largest BST Subtree (Solution) 334. Increasing Triplet Subsequence (Solution) 337. House Robber III (Solution) 338. Counting Bits (Solution) 341. Flatten Nested List Iterator (Solution) 342. Power of Four (Solution) 343. Integer Break (Solution) 344. Reverse String (Solution) 345. Reverse Vowels of a String (Solution) 346. Moving Average from Data Stream (Solution) 347. Top K Frequent Elements (Solution) 349. Intersection of Two Arrays (Solution) 350. Intersection of Two Arrays II (Solution) 351. Android Unlock Patterns (Solution) 353. Design Snake Game (Solution) 356. Line Reflection (Solution) 357. Count Numbers with Unique Digits (Solution) 360. Sort Transformed Array (Solution) 361. Bomb Enemy (Solution) 362. Design Hit Counter (Solution) 364. Nested List Weight Sum II (Solution) 365. Water and Jug Problem (Solution) 366. Find Leaves of Binary Tree (Solution) 367. Valid Perfect Square (Solution) 368. Largest Divisible Subset (Solution) 369. Plus One Linked List (Solution) 370. Range Addition (Solution) 371. Sum of Two Integers (Solution) 372. Super Pow (Solution) 373. Find K Pairs with Smallest Sums (Solution) 374. Guess Number Higher or Lower (Solution) 376. Wiggle Subsequence (Solution) 377. Combination Sum IV (Solution) 378. Kth Smallest Element in a Sorted Matrix (Solution) 379. Design Phone Directory (Solution) 380. Insert Delete GetRandom O(1) (Solution) 383. Ransom Note (Solution) 384. Shuffle an Array (Solution) 385. Mini Parser (Solution) 386. Lexicographical Numbers (Solution) 387. First Unique Character in a String (Solution) 388. Longest Absolute File Path (Solution) 389. Find the Difference (Solution) 390. Elimination Game (Solution) 392. Is Subsequence (Solution) 393. UTF-8 Validation (Solution) 394. Decode String (Solution) 395. Longest Substring with At Least K Repeating Characters (Solution) 396. Rotate Function (Solution) 397. Integer Replacement (Solution) 398. Random Pick Index (Solution) 399. Evaluate Division (Solution) 401. Binary Watch (Solution) 402. Remove K Digits (Solution) 404. Sum of Left Leaves (Solution) 405. Convert a Number to Hexadecimal (Solution) 406. Queue Reconstruction by Height (Solution) 409. Longest Palindrome (Solution) 412. Fizz Buzz (Solution) 413. Arithmetic Slices (Solution) 414. Third Maximum Number (Solution) 415. Add Strings (Solution) 416. Partition Equal Subset Sum (Solution) 417. Pacific Atlantic Water Flow (Solution) 418. Sentence Screen Fitting (Solution) 419. Battleships in a Board (Solution) 421. Maximum XOR of Two Numbers in an Array (Solution) 423. Reconstruct Original Digits from English (Solution) 424. Longest Repeating Character Replacement (Solution) 432. All O`one Data Structure (Solution) 434. Number of Segments in a String (Solution) 435. Non-overlapping Intervals (Solution) 436. Find Right Interval (Solution) 437. Path Sum III (Solution) 438. Find All Anagrams in a String (Solution) 439. Ternary Expression Parser (Solution) 441. Arranging Coins (Solution) 442. Find All Duplicates in an Array (Solution) 445. Add Two Numbers II (Solution) 448. Find All Numbers Disappeared in an Array (Solution) 449. Serialize and Deserialize BST (Solution) 450. Delete Node in a BST (Solution) 451. Sort Characters By Frequency (Solution) 452. Minimum Number of Arrows to Burst Balloons (Solution) 453. Minimum Moves to Equal Array Elements (Solution) 454. 4Sum II (Solution) 455. Assign Cookies (Solution) 456. 132 Pattern (Solution) 459. Repeated Substring Pattern (Solution) 460. LFU Cache (Solution) 461. Hamming Distance (Solution) 462. Minimum Moves to Equal Array Elements II (Solution) 463. Island Perimeter (Solution) 467. Unique Substrings in Wraparound String (Solution) 468. Validate IP Address (Solution) 469. Convex Polygon (Solution) 473. Matchsticks to Square (Solution) 474. Ones and Zeroes (Solution) 475. Heaters (Solution) 476. Number Complement (Solution) 477. Total Hamming Distance (Solution) 481. Magical String (Solution) 484. Find Permutation (Solution) 485. Max Consecutive Ones (Solution) 486. Predict the Winner (Solution) 487. Max Consecutive Ones II (Solution) 490. The Maze (Solution) 491. Increasing Subsequences (Solution) 492. Construct the Rectangle (Solution) 494. Target Sum (Solution) 495. Teemo Attacking (Solution) 496. Next Greater Element I (Solution) 498. Diagonal Traverse (Solution) 500. Keyboard Row (Solution) 501. Find Mode in Binary Search Tree (Solution) 503. Next Greater Element II (Solution) 504. Base 7 (Solution) 505. The Maze II (Solution) 506. Relative Ranks (Solution) 507. Perfect Number (Solution) 508. Most Frequent Subtree Sum (Solution) 513. Find Bottom Left Tree Value (Solution) 515. Find Largest Value in Each Tree Row (Solution) 516. Longest Palindromic Subsequence (Solution) 518. Coin Change 2 (Solution) 520. Detect Capital (Solution) 521. Longest Uncommon Subsequence I (Solution) 522. Longest Uncommon Subsequence II (Solution) 523. Continuous Subarray Sum (Solution) 524. Longest Word in Dictionary through Deleting (Solution) 525. Contiguous Array (Solution) 526. Beautiful Arrangement (Solution) 529. Minesweeper (Solution) 530. Minimum Absolute Difference in BST (Solution) 531. Lonely Pixel I (Solution) 532. K-diff Pairs in an Array (Solution) 533. Lonely Pixel II (Solution) 535. Encode and Decode TinyURL (Solution) 536. Construct Binary Tree from String (Solution) 537. Complex Number Multiplication (Solution) 538. Convert BST to Greater Tree (Solution) 539. Minimum Time Difference (Solution) 540. Single Element in a Sorted Array (Solution) 541. Reverse String II (Solution) 542. 01 Matrix (Solution) 543. Diameter of Binary Tree (Solution) 544. Output Contest Matches (Solution) 545. Boundary of Binary Tree (Solution) 547. Friend Circles (Solution) 548. Split Array with Equal Sum (Solution) 549. Binary Tree Longest Consecutive Sequence II (Solution) 551. Student Attendance Record I (Solution) 553. Optimal Division (Solution) 554. Brick Wall (Solution) 555. Split Concatenated Strings (Solution) 556. Next Greater Element III (Solution) 557. Reverse Words in a String III (Solution) 560. Subarray Sum Equals K (Solution) 561. Array Partition I (Solution) 562. Longest Line of Consecutive One in Matrix (Solution) 563. Binary Tree Tilt (Solution) 565. Array Nesting (Solution) 566. Reshape the Matrix (Solution) 567. Permutation in String (Solution) 572. Subtree of Another Tree (Solution) 573. Squirrel Simulation (Solution) 576. Out of Boundary Paths (Solution) 582. Kill Process (Solution) 583. Delete Operation for Two Strings (Solution) 592. Fraction Addition and Subtraction (Solution) 593. Valid Square (Solution) 609. Find Duplicate File in System (Solution) 611. Valid Triangle Number (Solution) 616. Add Bold Tag in String (Solution) 621. Task Scheduler (Solution) 623. Add One Row to Tree (Solution) 625. Minimum Factorization (Solution) 634. Find the Derangement of An Array (Solution) 636. Exclusive Time of Functions (Solution) 638. Shopping Offers (Solution) 640. Solve the Equation (Solution) 646. Maximum Length of Pair Chain (Solution) 647. Palindromic Substrings (Solution) 648. Replace Words (Solution) 649. Dota2 Senate (Solution) 650. 2 Keys Keyboard (Solution) 651. 4 Keys Keyboard (Solution) 652. Find Duplicate Subtrees (Solution) 654. Maximum Binary Tree (Solution) 655. Print Binary Tree (Solution) 658. Find K Closest Elements (Solution) 659. Split Array into Consecutive Subsequences (Solution) 662. Maximum Width of Binary Tree (Solution) 663. Equal Tree Partition (Solution) 666. Path Sum IV (Solution) 667. Beautiful Arrangement II (Solution) 670. Maximum Swap (Solution) 672. Bulb Switcher II (Solution) 673. Number of Longest Increasing Subsequence (Solution) 675. Cut Off Trees for Golf Event (Solution) 676. Implement Magic Dictionary (Solution) 677. Map Sum Pairs (Solution) 678. Valid Parenthesis String (Solution) 681. Next Closest Time (Solution) 684. Redundant Connection (Solution) 685. Redundant Connection II (Solution) 688. Knight Probability in Chessboard (Solution) 690. Employee Importance (Solution) 692. Top K Frequent Words (Solution) 694. Number of Distinct Islands (Solution) 698. Partition to K Equal Sum Subsets (Solution) 699. Falling Squares (Solution) 711. Number of Distinct Islands II (Solution) 712. Minimum ASCII Delete Sum for Two Strings (Solution) 713. Subarray Product Less Than K (Solution) 716. Max Stack (Solution) 718. Maximum Length of Repeated Subarray (Solution) 722. Remove Comments (Solution) 723. Candy Crush (Solution) 725. Split Linked List in Parts (Solution) 729. My Calendar I (Solution) 733. Flood Fill (Solution) 734. Sentence Similarity (Solution) 735. Asteroid Collision (Solution) 737. Sentence Similarity II (Solution) 738. Monotone Increasing Digits (Solution) 739. Daily Temperatures (Solution) 740. Delete and Earn (Solution) 742. Closest Leaf in a Binary Tree (Solution) 743. Network Delay Time (Solution) 748. Shortest Completing Word (Solution) 750. Number Of Corner Rectangles (Solution) 752. Open the Lock (Solution) 754. Reach a Number (Solution) 755. Pour Water (Solution) 756. Pyramid Transition Matrix (Solution) 763. Partition Labels (Solution) 764. Largest Plus Sign (Solution) 767. Reorganize String (Solution) 768. Max Chunks To Make Sorted II (Solution) 769. Max Chunks To Make Sorted (Solution) 775. Global and Local Inversions (Solution) 777. Swap Adjacent in LR String (Solution) 779. K-th Symbol in Grammar (Solution) 781. Rabbits in Forest (Solution) 785. Is Graph Bipartite? (Solution) 787. Cheapest Flights Within K Stops (Solution) 789. Escape The Ghosts (Solution) 791. Custom Sort String (Solution) 792. Number of Matching Subsequences (Solution) 795. Number of Subarrays with Bounded Maximum (Solution) 797. All Paths From Source to Target (Solution)