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LeetCode OJ is a platform for preparing technical coding interviews. Pick from an expanding library of more than 190 questions, code and submit your solution to see if you have solved it correctly. It is that easy!
Problems & Solutions
Here's my solutions of leetcode problems, and I'll keep it up to date. If you have any ideas about my solution, welcome to post a comment.
(tip: 🔒 means you need to buy a book from LeetCode)
Algorithms category
| # | Title | Solutions | Difficulty |
|---|---|---|---|
| 1 | Two Sum | C++ | Medium |
| 2 | Add Two Numbers | C++ | Medium |
| 3 | Longest Substring Without Repeating Characters | C++ | Medium |
| 4 | Median of Two Sorted Arrays | C | Hard |
| 5 | Longest Palindromic Substring | C++ | Medium |
| 6 | ZigZag Conversion | C++ | Easy |
| 7 | Reverse Integer | C++ | Easy |
| 8 | String to Integer (atoi) | C++ | Easy |
| 9 | Palindrome Number | C++ | Easy |
| 10 | Regular Expression Matching | C | Hard |
| 11 | Container With Most Water | C++ | Medium |
| 12 | Integer to Roman | C++ | Medium |
| 13 | Roman to Integer | C++ | Easy |
| 14 | Longest Common Prefix | C++ | Easy |
| 15 | 3Sum | C++ | Medium |
| 16 | 3Sum Closest | C++ | Medium |
| 17 | Letter Combinations of a Phone Number | C++ | Medium |
| 18 | 4Sum | C++ | Medium |
| 19 | Remove Nth Node From End of List | C++ | Easy |
| 20 | Valid Parentheses | C++ | Easy |
| 21 | Merge Two Sorted Lists | C++ | Easy |
| 22 | Generate Parentheses | C++ | Medium |
| 23 | Merge k Sorted Lists | C++ | Hard |
| 24 | Swap Nodes in Pairs | C++ | Medium |
| 25 | Reverse Nodes in k-Group | C++ | Hard |
| 26 | Remove Duplicates from Sorted Array | C++ | Easy |
| 27 | Remove Element | C++ | Easy |
| 28 | Implement strStr() | C | Easy |
| 29 | Divide Two Integers | C | Medium |
| 30 | Substring with Concatenation of All Words | C++ | Hard |
| 31 | Next Permutation | C++ | Medium |
| 32 | Longest Valid Parentheses | C++ | Hard |
| 33 | Search in Rotated Sorted Array | C++ | Hard |
| 34 | Search for a Range | C++ | Medium |
| 35 | Search Insert Position | C++ | Medium |
| 36 | Valid Sudoku | C++ | Easy |
| 37 | Sudoku Solver | C++ | Hard |
| 38 | Count and Say | C++ | Easy |
| 39 | Combination Sum | C++ | Medium |
| 40 | Combination Sum II | C++ | Medium |
| 41 | First Missing Positive | C++ | Hard |
| 42 | Trapping Rain Water | C++ | Hard |
| 43 | Multiply Strings | C++ | Medium |
| 44 | Wildcard Matching | C++ | Hard |
| 45 | Jump Game II | C++ | Hard |
| 46 | Permutations | C++ | Medium |
| 47 | Permutations II | C++ | Hard |
| 48 | Rotate Image | C++ | Medium |
| 49 | Group Anagrams | C++ | Medium |
| 50 | Pow(x, n) | C++ | Medium |
| 51 | N-Queens | C++ | Hard |
| 52 | N-Queens II | C++ | Hard |
| 53 | Maximum Subarray | C++ | Medium |
| 54 | Spiral Matrix | C++ | Medium |
| 55 | Jump Game | C++ | Medium |
| 56 | Merge Intervals | C++ | Hard |
| 57 | Insert Interval | C++ | Hard |
| 58 | Length of Last Word | C++ | Easy |
| 59 | Spiral Matrix II | C++ | Medium |
| 60 | Permutation Sequence | C++ | Medium |
| 61 | Rotate List | C++ | Medium |
| 62 | Unique Paths | C++ | Medium |
| 63 | Unique Paths II | C++ | Medium |
| 64 | Minimum Path Sum | C++ | Medium |
| 65 | Valid Number | C | Hard |
| 66 | Plus One | C++ | Easy |
| 67 | Add Binary | C++ | Easy |
| 68 | Text Justification | C++ | Hard |
| 69 | Sqrt(x) | C++ | Medium |
| 70 | Climbing Stairs | C++ | Easy |
| 71 | Simplify Path | C++ | Medium |
| 72 | Edit Distance | C++ | Hard |
| 73 | Set Matrix Zeroes | C++ | Medium |
| 74 | Search a 2D Matrix | C++ | Medium |
| 75 | Sort Colors | C++ | Medium |
| 76 | Minimum Window Substring | C++ | Hard |
| 77 | Combinations | C++ | Medium |
| 78 | Subsets | C++ | Medium |
| 79 | Word Search | C++ | Medium |
| 80 | Remove Duplicates from Sorted Array II | C++ | Medium |
| 81 | Search in Rotated Sorted Array II | C++ | Medium |
| 82 | Remove Duplicates from Sorted List II | C++ | Medium |
| 83 | Remove Duplicates from Sorted List | C++ | Easy |
| 84 | Largest Rectangle in Histogram | C++ | Hard |
| 85 | Maximal Rectangle | C++ | Hard |
| 86 | Partition List | C++ | Medium |
| 87 | Scramble String | C++ | Hard |
| 88 | Merge Sorted Array | C++ | Easy |
| 89 | Gray Code | C++ | Medium |
| 90 | Subsets II | C++ | Medium |
| 91 | Decode Ways | C++ | Medium |
| 92 | Reverse Linked List II | C++ | Medium |
| 93 | Restore IP Addresses | C++ | Medium |
| 94 | Binary Tree Inorder Traversal | C++ | Medium |
| 95 | Unique Binary Search Trees II | C++ | Medium |
| 96 | Unique Binary Search Trees | C++ | Medium |
| 97 | Interleaving String | C++ | Hard |
| 98 | Validate Binary Search Tree | C++ | Medium |
| 99 | Recover Binary Search Tree | C++ | Hard |
| 100 | Same Tree | C++ | Easy |
| 101 | Symmetric Tree | C++ | Easy |
| 102 | Binary Tree Level Order Traversal | C++ | Easy |
| 103 | Binary Tree Zigzag Level Order Traversal | C++ | Medium |
| 104 | Maximum Depth of Binary Tree | C++ | Easy |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | C++ | Medium |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | C++ | Medium |
| 107 | Binary Tree Level Order Traversal II | C++ | Easy |
| 108 | Convert Sorted Array to Binary Search Tree | C++ | Medium |
| 109 | Convert Sorted List to Binary Search Tree | C++ | Medium |
| 110 | Balanced Binary Tree | C++ | Easy |
| 111 | Minimum Depth of Binary Tree | C++ | Easy |
| 112 | Path Sum | C++ | Easy |
| 113 | Path Sum II | C++ | Medium |
| 114 | Flatten Binary Tree to Linked List | C++ | Medium |
| 115 | Distinct Subsequences | C++ | Hard |
| 116 | Populating Next Right Pointers in Each Node | C++ | Medium |
| 117 | Populating Next Right Pointers in Each Node II | C++ | Hard |
| 118 | Pascal's Triangle | C++ | Easy |
| 119 | Pascal's Triangle II | C++ | Easy |
| 120 | Triangle | C++ | Medium |
| 121 | Best Time to Buy and Sell Stock | C++ | Medium |
| 122 | Best Time to Buy and Sell Stock II | C++ | Medium |
| 123 | Best Time to Buy and Sell Stock III | C++ | Hard |
| 124 | Binary Tree Maximum Path Sum | C++ | Hard |
| 125 | Valid Palindrome | C++ | Easy |
| 126 | Word Ladder II | C++ | Hard |
| 127 | Word Ladder | C++ | Medium |
| 128 | Longest Consecutive Sequence | C++ | Hard |
| 129 | Sum Root to Leaf Numbers | C++ | Medium |
| 130 | Surrounded Regions | C++ | Medium |
| 131 | Palindrome Partitioning | C++ | Medium |
| 132 | Palindrome Partitioning II | C++ | Hard |
| 133 | Clone Graph | C++ | Medium |
| 134 | Gas Station | C++ | Medium |
| 135 | Candy | C++ | Hard |
| 136 | Single Number | C++, C | Medium |
| 137 | Single Number II | C++ | Medium |
| 138 | Copy List with Random Pointer | C++ | Hard |
| 139 | Word Break | C++ | Medium |
| 140 | Word Break II | C++ | Hard |
| 141 | Linked List Cycle | C, C++ | Medium |
| 142 | Linked List Cycle II | C++ | Medium |
| 143 | Reorder List | C | Medium |
| 144 | Binary Tree Preorder Traversal | C++ | Medium |
| 145 | Binary Tree Postorder Traversal | C++ | Hard |
| 146 | LRU Cache | C++, Python | Hard |
| 147 | Insertion Sort List | C | Medium |
| 148 | Sort List | C++ | Medium |
| 149 | Max Points on a Line | C++ | Hard |
| 150 | Evaluate Reverse Polish Notation | C++ | Medium |
| 151 | Reverse Words in a String | C++ | Medium |
| 152 | Maximum Product Subarray | C++ | Medium |
| 153 | Find Minimum in Rotated Sorted Array | C++ | Medium |
| 154 | Find Minimum in Rotated Sorted Array II | C++ | Hard |
| 155 | Min Stack | C++ | Easy |
| 156 | 🔒 Binary Tree Upside Down | Medium | |
| 157 | 🔒 Read N Characters Given Read4 | Easy | |
| 158 | 🔒 Read N Characters Given Read4 II - Call multiple times | Hard | |
| 159 | 🔒 Longest Substring with At Most Two Distinct Characters | Hard | |
| 160 | Intersection of Two Linked Lists | C, C++ | Easy |
| 161 | 🔒 One Edit Distance | Medium | |
| 162 | Find Peak Element | C++ | Medium |
| 163 | 🔒 Missing Ranges | Medium | |
| 164 | Maximum Gap | C++ | Hard |
| 165 | Compare Version Numbers | C++ | Easy |
| 166 | Fraction to Recurring Decimal | C++ | Medium |
| 167 | Two Sum II - Input array is sorted | C++ | Medium |
| 168 | Excel Sheet Column Title | C++ | Easy |
| 169 | Majority Element | C++ | Easy |
| 170 | 🔒 Two Sum III - Data structure design | Easy | |
| 171 | Excel Sheet Column Number | C++ | Easy |
| 172 | Factorial Trailing Zeroes | C++ | Easy |
| 173 | Binary Search Tree Iterator | C++ | Medium |
| 174 | Dungeon Game | C++ | Hard |
| 179 | Largest Number | C++ | Medium |
| 186 | 🔒 Reverse Words in a String II | Medium | |
| 187 | Repeated DNA Sequences | C++ | Medium |
| 188 | Best Time to Buy and Sell Stock IV | C++ | Hard |
| 189 | Rotate Array | C++ | Easy |
| 190 | Reverse Bits | C | Easy |
| 191 | Number of 1 Bits | C | Easy |
| 198 | House Robber | C++ | Easy |
| 199 | Binary Tree Right Side View | C++ | Medium |
| 200 | Number of Islands | C++ | Medium |
| 201 | Bitwise AND of Numbers Range | C | Medium |
| 202 | Happy Number | C++ | Easy |
| 203 | Remove Linked List Elements | C++ | Easy |
| 204 | Count Primes | C++ | Easy |
| 205 | Isomorphic Strings | C++ | Easy |
| 206 | Reverse Linked List | C++ | Easy |
| 207 | Course Schedule | C++ | Medium |
| 208 | Implement Trie (Prefix Tree) | C++ | Medium |
| 209 | Minimum Size Subarray Sum | C++ | Medium |
| 210 | Course Schedule II | C++ | Medium |
| 211 | Add and Search Word - Data structure design | C++ | Medium |
| 212 | Word Search II | Hard | |
| 213 | House Robber II | Medium | |
| 214 | Shortest Palindrome | Hard | |
| 215 | Kth Largest Element in an Array | C++ | Medium |
| 216 | Combination Sum III | Medium | |
| 217 | Contains Duplicate | C++ | Easy |
| 218 | The Skyline Problem | Hard | |
| 219 | Contains Duplicate II | C++ | Easy |
| 220 | Contains Duplicate III | C++ | Medium |
| 226 | Invert Binary Tree | C++ | Easy |
| 231 | Power of Two | C++ | Easy |
| 232 | Implement Queue using Stacks | C++ | Easy |
| 233 | Number of Digit One | Hard | |
| 234 | Palindrome Linked List | C++ | Easy |
| 235 | Lowest Common Ancestor of a Binary Search Tree | C++ | Easy |
| 236 | Lowest Common Ancestor of a Binary Tree | C++ | Medium |
| 237 | Delete Node in a Linked List | C++ | Easy |
| 238 | Product of Array Except Self | Medium | |
| 239 | Sliding Window Maximum | Hard | |
| 240 | Search a 2D Matrix II | C++ | Medium |
| 241 | Different Ways to Add Parentheses | Medium | |
| 242 | Valid Anagram | C, C++, Java, Python | Easy |
| 243 | 🔒 Shortest Word Distance | Easy | |
| 244 | 🔒 Shortest Word Distance II | Medium | |
| 245 | 🔒 Shortest Word Distance III | Medium | |
| 246 | 🔒 Strobogrammatic Number | Easy | |
| 247 | 🔒 Strobogrammatic Number II | Medium | |
| 248 | 🔒 Strobogrammatic Number III | Hard | |
| 249 | 🔒 Group Shifted Strings | Easy | |
| 250 | 🔒 Count Univalue Subtrees | Medium | |
| 251 | 🔒 Flatten 2D Vector | Medium | |
| 252 | 🔒 Meeting Rooms | Easy | |
| 253 | 🔒 Meeting Rooms II | Medium | |
| 254 | 🔒 Factor Combinations | Medium | |
| 255 | 🔒 Verify Preorder Sequence in Binary Search Tree | Medium | |
| 256 | 🔒 Paint House | Medium | |
| 257 | Binary Tree Paths | C++ | Easy |
| 258 | Add Digits | C++ | Easy |
| 259 | 🔒 3Sum Smaller | Medium | |
| 260 | Single Number III | c++ | Medium |
| 261 | 🔒 Graph Valid Tree | Medium | |
| 263 | Ugly Number | Easy | |
| 264 | Ugly Number II | Medium | |
| 265 | 🔒 Paint House II | Hard | |
| 266 | 🔒 Palindrome Permutation | Easy | |
| 267 | 🔒 Palindrome Permutation II | Medium | |
| 268 | Missing Number | Medium | |
| 269 | 🔒 Alien Dictionary | Hard | |
| 270 | 🔒 Closest Binary Search Tree Value | Easy | |
| 271 | 🔒 Encode and Decode Strings | Medium | |
| 272 | 🔒 Closest Binary Search Tree Value II | Hard | |
| 273 | Integer to English Words | Hard | |
| 274 | H-Index | C++ | Medium |
| 275 | H-Index II | Medium | |
| 276 | 🔒 Paint Fence | Easy | |
| 277 | 🔒 Find the Celebrity | Medium | |
| 278 | First Bad Version | Easy | |
| 279 | Perfect Squares | Medium | |
| 280 | 🔒 Wiggle Sort | Medium | |
| 281 | 🔒 Zigzag Iterator | Medium | |
| 282 | Expression Add Operators | Hard | |
| 283 | Move Zeroes | Easy | |
| 284 | Peeking Iterator | Medium | |
| 285 | 🔒 Inorder Successor in BST | Medium | |
| 286 | 🔒 Walls and Gates | Medium | |
| 287 | Find the Duplicate Number | Hard | |
| 288 | 🔒 Unique Word Abbreviation | Easy | |
| 289 | Game of Life | Medium | |
| 290 | Word Pattern | Easy | |
| 291 | 🔒 Word Pattern II | Hard | |
| 292 | Nim Game | Easy | |
| 293 | 🔒 Flip Game | Easy | |
| 294 | 🔒 Flip Game II | Medium | |
| 295 | Find Median from Data Stream | Hard | |
| 296 | 🔒 Best Meeting Point | Hard | |
| 297 | Serialize and Deserialize Binary Tree | Hard | |
| 298 | 🔒 Binary Tree Longest Consecutive Sequence | Medium | |
| 299 | Bulls and Cows | Easy | |
| 300 | Longest Increasing Subsequence | Medium | |
| 301 | Remove Invalid Parentheses | Hard | |
| 302 | 🔒 Smallest Rectangle Enclosing Black Pixels | Hard | |
| 303 | Range Sum Query - Immutable | Easy | |
| 304 | Range Sum Query 2D - Immutable | Medium | |
| 305 | 🔒 Number of Islands II | Hard | |
| 306 | Additive Number | Medium | |
| 307 | Range Sum Query - Mutable | Medium | |
| 308 | 🔒 Range Sum Query 2D - Mutable | Hard | |
| 309 | Best Time to Buy and Sell Stock with Cooldown | Medium | |
| 310 | Minimum Height Trees | Medium | |
| 311 | 🔒 Sparse Matrix Multiplication | Medium | |
| 312 | Burst Balloons | Hard | |
| 313 | Super Ugly Number | Medium | |
| 314 | 🔒 Binary Tree Vertical Order Traversal | Medium | |
| 315 | Count of Smaller Numbers After Self | Hard | |
| 316 | Remove Duplicate Letters | Hard | |
| 317 | 🔒 Shortest Distance from All Buildings | Hard | |
| 318 | Maximum Product of Word Lengths | Medium | |
| 319 | Bulb Switcher | Medium | |
| 320 | 🔒 Generalized Abbreviation | Medium | |
| 321 | Create Maximum Number | Hard | |
| 322 | Coin Change | Medium | |
| 323 | 🔒 Number of Connected Components in an Undirected Graph | Medium | |
| 324 | Wiggle Sort II | Medium | |
| 325 | 🔒 Maximum Size Subarray Sum Equals k | Medium | |
| 326 | Power of Three | Easy | |
| 327 | Count of Range Sum | Hard | |
| 328 | Odd Even Linked List | Medium | |
| 329 | Longest Increasing Path in a Matrix | Hard | |
| 330 | Patching Array | Hard | |
| 331 | Verify Preorder Serialization of a Binary Tree | Medium | |
| 332 | Reconstruct Itinerary | Medium | |
| 333 | 🔒 Largest BST Subtree | Medium | |
| 334 | Increasing Triplet Subsequence | Medium | |
| 335 | Self Crossing | Hard | |
| 336 | Palindrome Pairs | Hard | |
| 337 | House Robber III | Medium | |
| 338 | Counting Bits | Medium | |
| 339 | 🔒 Nested List Weight Sum | Easy | |
| 340 | 🔒 Longest Substring with At Most K Distinct Characters | Hard | |
| 341 | Flatten Nested List Iterator | Medium | |
| 342 | Power of Four | Easy | |
| 343 | Integer Break | Medium | |
| 344 | Reverse String | Easy | |
| 345 | Reverse Vowels of a String | Easy | |
| 346 | 🔒 Moving Average from Data Stream | Easy | |
| 347 | Top K Frequent Elements | Medium | |
| 348 | 🔒 Design Tic-Tac-Toe | Medium | |
| 349 | Intersection of Two Arrays | Easy | |
| 350 | Intersection of Two Arrays II | Easy | |
| 351 | 🔒 Android Unlock Patterns | Medium | |
| 352 | Data Stream as Disjoint Intervals | Hard | |
| 353 | 🔒 Design Snake Game | Medium | |
| 354 | Russian Doll Envelopes | Hard | |
| 355 | Design Twitter | Medium | |
| 356 | 🔒 Line Reflection | Medium | |
| 357 | Count Numbers with Unique Digits | Medium | |
| 358 | 🔒 Rearrange String k Distance Apart | Hard | |
| 359 | 🔒 Logger Rate Limiter | Easy | |
| 360 | 🔒 Sort Transformed Array | Medium | |
| 361 | 🔒 Bomb Enemy | Medium | |
| 362 | 🔒 Design Hit Counter | Medium | |
| 363 | Max Sum of Rectangle No Larger Than K | Hard | |
| 364 | 🔒 Nested List Weight Sum II | Medium | |
| 365 | Water and Jug Problem | Medium | |
| 366 | 🔒 Find Leaves of Binary Tree | Medium | |
| 367 | Valid Perfect Square | Medium | |
| 368 | Largest Divisible Subset | Medium | |
| 369 | 🔒 Plus One Linked List | Medium | |
| 370 | 🔒 Range Addition | Medium | |
| 371 | Sum of Two Integers | Easy | |
| 372 | Super Pow | Medium | |
| 373 | Find K Pairs with Smallest Sums | Medium | |
| 374 | Guess Number Higher or Lower | Easy | |
| 375 | Guess Number Higher or Lower II | Medium | |
| 376 | Wiggle Subsequence | Medium | |
| 377 | Combination Sum IV | Medium | |
| 378 | Kth Smallest Element in a Sorted Matrix | Medium | |
| 379 | 🔒 Design Phone Directory | Medium | |
| 380 | Insert Delete GetRandom O(1) | Medium | |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | Hard | |
| 382 | Linked List Random Node | Medium | |
| 383 | Ransom Note | Easy | |
| 384 | Shuffle an Array | Medium | |
| 385 | Mini Parser | Medium | |
| 386 | Lexicographical Numbers | Medium | |
| 387 | First Unique Character in a String | Easy | |
| 388 | Longest Absolute File Path | Medium | |
| 389 | Find the Difference | C++, Java | Easy |
| 391 | Perfect Rectangle | Hard | |
| 392 | Is Subsequence | Medium | |
| 393 | UTF-8 Validation | Medium | |
| 394 | Decode String | Medium | |
| 395 | Longest Substring with At Least K Repeating Characters | Medium | |
| 396 | Rotate Function | Medium | |
| 397 | Integer Replacement | Medium | |
| 398 | Random Pick Index | Medium | |
| 399 | Evaluate Division | Medium | |
| 400 | Nth Digit | Easy | |
| 401 | Binary Watch | Easy | |
| 402 | Remove K Digits | Medium | |
| 403 | Frog Jump | Hard | |
| 404 | Sum of Left Leaves | Easy | |
| 405 | Convert a Number to Hexadecimal | Easy | |
| 406 | Queue Reconstruction by Height | Medium | |
| 407 | Trapping Rain Water II | Hard | |
| 408 | Valid Word Abbreviation | Easy | |
| 409 | Longest Palindrome | Easy | |
| 410 | Split Array Largest Sum | Hard | |
| 411 | Minimum Unique Word Abbreviation | Hard | |
| 412 | Fizz Buzz | Easy | |
| 413 | Arithmetic Slices | Medium | |
| 414 | Third Maximum Number | Easy | |
| 415 | Add Strings | Easy | |
| 416 | Partition Equal Subset Sum | Medium | |
| 417 | Pacific Atlantic Water Flow | Medium | |
| 418 | Sentence Screen Fitting | Medium | |
| 419 | Battleships in a Board | Medium | |
| 420 | Strong Password Checker | Hard | |
| 421 | Maximum XOR of Two Numbers in an Array | Medium | |
| 422 | Valid Word Square | Easy | |
| 423 | Reconstruct Original Digits from English | Medium | |
| 424 | Longest Repeating Character Replacement | Medium | |
| 425 | Word Squares | Hard | |
| 432 | All O`one Data Structure | Hard | |
| 434 | Number of Segments in a String | Easy | |
| 435 | Non-overlapping Intervals | Medium | |
| 436 | Find Right Interval | Medium | |
| 437 | Path Sum III | Easy | |
| 438 | Find All Anagrams in a String | Easy | |
| 439 | Ternary Expression Parser | Medium | |
| 440 | K-th Smallest in Lexicographical Order | Hard | |
| 441 | Arranging Coins | Easy | |
| 442 | Find All Duplicates in an Array | Medium | |
| 444 | Sequence Reconstruction | Medium | |
| 445 | Add Two Numbers II | Medium | |
| 446 | Arithmetic Slices II - Subsequence | Hard | |
| 447 | Number of Boomerangs | Easy | |
| 448 | Find All Numbers Disappeared in an Array | Easy | |
| 449 | Serialize and Deserialize BST | Medium | |
| 450 | Delete Node in a BST | Medium | |
| 451 | Sort Characters By Frequency | Medium | |
| 452 | Minimum Number of Arrows to Burst Balloons | Medium | |
| 453 | Minimum Moves to Equal Array Elements | Easy | |
| 454 | 4Sum II | C++ | Medium |
| 455 | Assign Cookies | Easy | |
| 456 | 132 Pattern | Medium | |
| 459 | Repeated Substring Pattern | Easy | |
| 460 | LFU Cache | Hard | |
| 461 | Hamming Distance | Easy | |
| 462 | Minimum Moves to Equal Array Elements II | Medium | |
| 463 | Island Perimeter | Easy | |
| 464 | Can I Win | Medium | |
| 465 | Optimal Account Balancing | Hard | |
| 466 | Count The Repetitions | Hard | |
| 467 | Unique Substrings in Wraparound String | Medium | |
| 468 | Validate IP Address | Medium | |
| 469 | Convex Polygon | Medium | |
| 471 | Encode String with Shortest Length | Hard | |
| 472 | Concatenated Words | Hard | |
| 473 | Matchsticks to Square | Medium | |
| 474 | Ones and Zeroes | Medium | |
| 475 | Heaters | Easy | |
| 476 | Number Complement | Easy | |
| 477 | Total Hamming Distance | Medium | |
| 480 | Sliding Window Median | Hard | |
| 481 | Magical String | Medium | |
| 482 | License Key Formatting | Medium | |
| 483 | Smallest Good Base | Hard | |
| 484 | Find Permutation | Medium | |
| 485 | Max Consecutive Ones | Easy | |
| 486 | Predict the Winner | Medium | |
| 487 | Max Consecutive Ones II | Medium | |
| 488 | Zuma Game | Hard | |
| 490 | The Maze | Medium | |
| 491 | Increasing Subsequences | Medium | |
| 492 | Construct the Rectangle | Easy | |
| 493 | Reverse Pairs | Hard | |
| 494 | Target Sum | Medium | |
| 495 | Teemo Attacking | Medium | |
| 496 | Next Greater Element I | Easy | |
| 498 | Diagonal Traverse | Medium | |
| 499 | The Maze III | Hard | |
| 500 | Keyboard Row | Easy | |
| 501 | Find Mode in Binary Search Tree | Easy | |
| 502 | IPO | Hard | |
| 503 | Next Greater Element II | Medium | |
| 504 | Base 7 | Easy | |
| 505 | The Maze II | Medium | |
| 506 | Relative Ranks | Easy | |
| 507 | Perfect Number | Easy | |
| 508 | Most Frequent Subtree Sum | Medium | |
| 513 | Find Bottom Left Tree Value | Medium | |
| 514 | Freedom Trail | Hard | |
| 515 | Find Largest Value in Each Tree Row | Medium | |
| 516 | Longest Palindromic Subsequence | Medium | |
| 517 | Super Washing Machines | Hard | |
| 520 | Detect Capital | Easy | |
| 521 | Longest Uncommon Subsequence I | Easy | |
| 522 | Longest Uncommon Subsequence II | Medium | |
| 523 | Continuous Subarray Sum | Medium | |
| 524 | Longest Word in Dictionary through Deleting | Medium | |
| 525 | Contiguous Array | Medium | |
| 526 | Beautiful Arrangement | Medium | |
| 527 | Word Abbreviation | Hard | |
| 529 | Minesweeper | Medium | |
| 530 | Minimum Absolute Difference in BST | Easy | |
| 531 | Lonely Pixel I | Medium | |
| 532 | K-diff Pairs in an Array | Easy | |
| 533 | Lonely Pixel II | Medium | |
| 535 | Encode and Decode TinyURL | C++ | Medium |
| 536 | Construct Binary Tree from String | Medium | |
| 537 | Complex Number Multiplication | Medium | |
| 538 | Convert BST to Greater Tree | Medium | |
| 539 | Minimum Time Difference | Medium | |
| 541 | Reverse String II | Easy | |
| 542 | 01 Matrix | Medium | |
| 543 | Diameter of Binary Tree | Easy | |
| 544 | Output Contest Matches | Medium | |
| 545 | Boundary of Binary Tree | Medium | |
| 546 | Remove Boxes | Hard | |
| 547 | Friend Circles | Medium | |
| 548 | Split Array with Equal Sum | Medium | |
| 549 | Binary Tree Longest Consecutive Sequence II | C++ | Medium |
| 551 | Student Attendance Record I | C++ | Easy |
| 552 | Student Attendance Record II | Hard | |
| 553 | Optimal Division | C++ | Medium |
| 554 | Brick Wall | C++ | Medium |
| 555 | Split Assembled Strings | C++ | Hard |
| 556 | Next Greater Element III | C++ | Medium |
| 557 | Reverse Words in a String III | C++ | Easy |
| 560 | Subarray Sum Equals K New | Medium | |
| 561 | Array Partition I | Easy | |
| 562 | Longest Line of Consecutive One in Matrix | Medium | |
| 563 | Binary Tree Tilt | Easy | |
| 564 | Find the Closest Palindrome | Hard | |
| 566 | Reshape the Matrix | C++ | Easy |
| 567 | Permutation in String | C++ | Medium |
| 568 | Maximum Vacation Days New | Hard | |
| 652 | Find Duplicate Subtrees | C++ | Medium |
Concurrency category
| # | Title | Solutions | Difficulty |
|---|---|---|---|
| 1114 | Print in Order | C++ | Easy |
| 1115 | Print FooBar Alternately | C++ | Medium |
| 1116 | Print Zero Even Odd | C++ | Medium |
| 1117 | Building H2O | C++ | Medium |
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