The number of LeetCode questions is increasing every week. For more questions and solutions, you can see my LintCode repository. I'll keep updating for full summary and better solutions. Stay tuned for updates. (Notes: "📖" means you need to subscribe to LeetCode premium membership for the access to premium questions.)
- Bit Manipulation
- Array
- String
- Linked List
- Stack
- Queue
- Heap
- Tree
- Hash Table
- Math
- Two Pointers
- Sort
- Recursion
- Binary Search
- Binary Search Tree
- Breadth-First Search
- Depth-First Search
- Backtracking
- Dynamic Programming
- Greedy
- Graph
- Geometry
- Design
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 020 | Valid Parentheses | C++ Python | O(n) | O(n) | Easy | ||
| 032 | Longest Valid Parentheses | C++ Python | O(n) | O(1) | Hard | ||
| 071 | Simplify Path | C++ Python | O(n) | O(n) | Medium | ||
| 084 | Largest Rectangle in Histogram | C++ Python | O(n) | O(n) | Hard | Ascending Stack, DP | |
| 085 | Maximal Rectangle | C++ Python | O(m * n) | O(n) | Hard | EPI | Ascending Stack |
| 101 | Symmetric Tree | C++ Python | O(n) | O(h) | Easy | ||
| 150 | Evaluate Reverse Polish Notation | C++ Python | O(n) | O(n) | Medium | ||
| 155 | Min Stack | C++ Python | O(n) | O(1) | Easy | ||
| 173 | Binary Search Tree Iterator | C++ Python | O(1) | O(h) | Medium | ||
| 224 | Basic Calculator | C++ Python | O(n) | O(n) | Hard | ||
| 227 | Basic Calculator II | C++ Python | O(n) | O(n) | Medium | ||
| 232 | Implement Queue using Stacks | C++ Python | O(1), amortized | O(n) | Easy | EPI, LintCode | |
| 255 | Verify Preorder Sequence in Binary Search Tree | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 272 | Closest Binary Search Tree Value II | C++ Python | O(h + k) | O(h) | Hard | 📖 | |
| 331 | Verify Preorder Serialization of a Binary Tree | C++ Python | O(n) | O(1) | Medium | ||
| 341 | Flatten Nested List Iterator | C++ Python | O(n) | O(h) | Medium | 📖 | Iterator |
| 385 | Mini Parser | C++ Python | O(n) | O(h) | Medium | ||
| 394 | Decode String | C++ Python | O(n) | O(h) | Medium | ||
| 439 | Ternary Expression Parser | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 456 | 132 Pattern | C++ Python | O(n) | O(n) | Medium | ||
| 636 | Exclusive Time of Functions | C++ Python | O(n) | O(n) | Medium | ||
| 682 | Baseball Game | C++ Python | O(n) | O(n) | Easy | ||
| 726 | Number of Atoms | C++ Python | O(n) | O(n) | Hard | ||
| 735 | Asteroid Collision | C++ Python | O(n) | O(n) | Medium | ||
| 736 | Parse Lisp Expression | C++ Python | O(n^2) | O(n^2) | Hard | ||
| 739 | Daily Temperatures | C++ Python | O(n) | O(n) | Medium | ||
| 770 | Basic Calculator IV | C++ Python | add: O(d * t) sub: O(d * t) mul: O(d * t^2) eval: O(d * t) to_list: O(d * tlogt) |
O(e + d * t) | Hard | ||
| 772 | Basic Calculator III | C++ Python | O(n) | O(n) | Hard |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 239 | Sliding Window Maximum | C++ Python | O(n) | O(k) | Hard | EPI, LintCode | |
| 281 | Zigzag Iterator | C++ Python | O(n) | O(k) | Medium | 📖 | |
| 346 | Moving Average from Data Stream | C++ Python | O(1) | O(w) | Easy | 📖 |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 264 | Ugly Number II | C++ Python | O(n) | O(1) | Medium | CTCI, LintCode | BST, Heap |
| 295 | Find Median from Data Stream | C++ Python | O(nlogn) | O(n) | Hard | EPI, LintCode | BST, Heap |
| 313 | Super Ugly Number | C++ Python | O(n * k) | O(n + k) | Medium | BST, Heap | |
| 358 | Rearrange String k Distance Apart | C++ Python | O(n) | O(n) | Hard | 📖 | Greedy, Heap |
| 373 | Find K Pairs with Smallest Sums | C++ Python | O(k * log(min(n, m, k))) | O(min(n, m, k)) | Medium | ||
| 378 | Kth Smallest Element in a Sorted Matrix | C++ Python | O(k * log(min(n, m, k))) | O(min(n, m, k)) | Medium | LintCode | |
| 407 | Trapping Rain Water II | C++ Python | O(m * n * (logm + logn)) | O(m * n) | Hard | LintCode | |
| 632 | Smallest Range | C++ Python | O(nlogk) | O(k) | Hard |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 094 | Binary Tree Inorder Traversal | C++ Python | O(n) | O(1) | Medium | Morris Traversal |
|
| 099 | Recover Binary Search Tree | C++ Python | O(n) | O(1) | Hard | Morris Traversal |
|
| 144 | Binary Tree Preorder Traversal | C++ Python | O(n) | O(1) | Medium | Morris Traversal |
|
| 145 | Binary Tree Postorder Traversal | C++ Python | O(n) | O(1) | Hard | Morris Traversal |
|
| 208 | Implement Trie (Prefix Tree) | C++ Python | O(n) | O(1) | Medium | Trie | |
| 211 | Add and Search Word - Data structure design | C++ Python | O(min(n, h)) | O(min(n, h)) | Medium | Trie, DFS | |
| 226 | Invert Binary Tree | C++ Python | O(n) | O(h), O(w) | Easy | ||
| 297 | Serialize and Deserialize Binary Tree | C++ Python | O(n) | O(h) | Hard | LintCode | DFS |
| 307 | Range Sum Query - Mutable | C++ Python | ctor: O(n), update: O(logn), query: O(logn) | O(n) | Medium | LintCode | DFS, Segment Tree, BIT |
| 308 | Range Sum Query 2D - Mutable | C++ Python | ctor: O(m * n), update: O(logm + logn), query: O(logm + logn) | O(m * n) | Hard | 📖 | DFS, Segment Tree, BIT |
| 315 | Count of Smaller Numbers After Self | C++ Python | O(nlogn) | O(n) | Hard | LintCode | BST, BIT, Divide and Conquer |
| 525 | Contiguous Array | C++ Python | O(n) | O(n) | Medium | ||
| 529 | Minesweeper | C++ Python | O(m * n) | O(m + n) | Medium | ||
| 536 | Construct Binary Tree from String | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 538 | Convert BST to Greater Tree | C++ Python | O(n) | O(h) | Easy | ||
| 543 | Diameter of Binary Tree | C++ Python | O(n) | O(h) | Easy | ||
| 545 | Boundary of Binary Tree | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 548 | Split Array with Equal Sum | C++ Python | O(n^2) | O(n) | Medium | 📖 | |
| 563 | Binary Tree Tilt | C++ Python | O(n) | O(n) | Easy | ||
| 572 | Subtree of Another Tree | C++ Python | O(m * n) | O(h) | Easy | ||
| 606 | Construct String from Binary Tree | C++ Python | O(n) | O(h) | Easy | ||
| 617 | Merge Two Binary Trees | C++ Python | O(n) | O(h) | Easy | ||
| 623 | Add One Row to Tree | C++ Python | O(n) | O(h) | Medium | ||
| 637 | Average of Levels in Binary Tree | C++ Python | O(n) | O(h) | Easy | ||
| 652 | Find Duplicate Subtrees | C++ Python | O(n) | O(n) | Medium | DFS, Hash | |
| 653 | Two Sum IV - Input is a BST | C++ Python | O(n) | O(h) | Easy | Two Pointers | |
| 654 | Maximum Binary Tree | C++ Python | O(n) | O(n) | Medium | LintCode | Descending Stack |
| 655 | Print Binary Tree | C++ Python | O(n) | O(h) | Medium | ||
| 662 | Maximum Width of Binary Tree | C++ Python | O(n) | O(h) | Medium | DFS | |
| 663 | Equal Tree Partition | C++ Python | O(n) | O(n) | Medium | 📖 | Hash |
| 677 | Map Sum Pairs | C++ Python | O(n) | O(t) | Medium | Trie | |
| 684 | Redundant Connection | C++ Python | O(n) | O(n) | Medium | Union Find | |
| 685 | Redundant Connection II | C++ Python | O(n) | O(n) | Hard | Union Find | |
| 687 | Longest Univalue Path | C++ Python | O(n) | O(h) | Easy | ||
| 699 | Falling Squares | C++ Python | O(nlogn) | O(n) | Hard | Segment Tree |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 007 | Reverse Integer | C++ Python | O(1) | O(1) | Easy | ||
| 009 | Palindrome Number | C++ Python | O(1) | O(1) | Easy | ||
| 012 | Integer to Roman | C++ Python | O(n) | O(1) | Medium | ||
| 013 | Roman to Integer | C++ Python | O(n) | O(1) | Easy | ||
| 029 | Divide Two Integers | C++ Python | O(1) | O(1) | Medium | ||
| 050 | Pow(x, n) | C++ Python | O(1) | O(1) | Medium | ||
| 060 | Permutation Sequence | C++ Python | O(n^2) | O(n) | Medium | Cantor Ordering |
|
| 065 | Valid Number | C++ Python | O(n) | O(1) | Hard | Automata |
|
| 089 | Gray Code | C++ Python | O(2^n) | O(1) | Medium | ||
| 166 | Fraction to Recurring Decimal | C++ Python | O(logn) | O(1) | Medium | ||
| 168 | Excel Sheet Column Title | C++ Python | O(logn) | O(1) | Easy | ||
| 171 | Excel Sheet Column Number | C++ Python | O(n) | O(1) | Easy | ||
| 172 | Factorial Trailing Zeroes | C++ Python | O(1) | O(1) | Easy | ||
| 223 | Rectangle Area | C++ Python | O(1) | O(1) | Easy | ||
| 233 | Number of Digit One | C++ Python | O(1) | O(1) | Hard | CTCI, LintCode | |
| 248 | Strobogrammatic Number III | C++ Python | O(5^(n/2)) | O(n) | Hard | 📖 | |
| 258 | Add Digits | C++ Python | O(1) | O(1) | Easy | ||
| 263 | Ugly Number | C++ Python | O(1) | O(1) | Easy | ||
| 292 | Nim Game | C++ Python | O(1) | O(1) | Easy | LintCode | |
| 319 | Bulb Switcher | C++ Python | O(1) | O(1) | Medium | ||
| 326 | Power of Three | C++ Python | O(1) | O(1) | Easy | ||
| 335 | Self Crossing | C++ Python | O(n) | O(1) | Hard | ||
| 338 | Counting Bits | C++ Python | O(n) | O(n) | Medium | ||
| 343 | Integer Break | C++ Python | O(logn) | O(1) | Medium | Tricky, DP | |
| 365 | Water and Jug Problem | C++ Python | O(logn) | O(1) | Medium | Bézout's identity |
|
| 372 | Super Pow | C++ Python | O(n) | O(1) | Medium | ||
| 382 | Linked List Random Node | C++ Python | O(n) | O(1) | Medium | Reservoir Sampling |
|
| 386 | Lexicographical Numbers | C++ Python | O(n) | O(1) | Medium | ||
| 390 | Elimination Game | C++ Python | O(logn) | O(1) | Medium | ||
| 391 | Perfect Rectangle | C++ Python | O(n) | O(n) | Hard | ||
| 398 | Random Pick Index | C++ Python | O(n) | O(1) | Medium | Reservoir Sampling |
|
| 400 | Nth Digit | C++ Python | O(logn) | O(1) | Easy | ||
| 413 | Arithmetic Slices | C++ Python | O(n) | O(1) | Medium | ||
| 423 | Reconstruct Original Digits from English | C++ Python | O(n) | O(1) | Medium | GCJ2016 - Round 1B | |
| 441 | Arranging Coins | C++ Python | O(nlogn) | O(1) | Easy | Binary Search | |
| 453 | Minimum Moves to Equal Array Elements | C++ Python | O(n) | O(1) | Easy | ||
| 458 | Poor Pigs | C++ Python | O(n) | O(1) | Easy | ||
| 469 | Convex Polygon | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 537 | Complex Number Multiplication | C++ Python | O(1) | O(1) | Medium | ||
| 553 | Optimal Division | C++ Python | O(n) | O(1) | Medium | ||
| 573 | Squirrel Simulation | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 592 | Fraction Addition and Subtraction | C++ Python | O(nlogx) | O(n) | Medium | ||
| 593 | Valid Square | C++ Python | O(1) | O(1) | Medium | ||
| 598 | Range Addition II | C++ Python | O(p) | O(1) | Easy | ||
| 625 | Minimum Factorization | C++ Python | O(loga) | O(1) | Medium | 📖 | |
| 628 | Maximum Product of Three Numbers | C++ Python | O(n) | O(1) | Easy | ||
| 633 | Sum of Square Numbers | C++ Python | O(sqrt(c) * logc) | O(1) | Easy | ||
| 634 | Find the Derangement of An Array | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 640 | Solve the Equation | C++ Python | O(n) | O(n) | Medium | ||
| 651 | 4 Keys Keyboard | C++ Python | O(1) | O(1) | Medium | 📖 | Math, DP |
| 660 | Remove 9 | C++ Python | O(logn) | O(1) | Hard | 📖 | |
| 672 | Bulb Switcher II | C++ Python | O(1) | O(1) | Medium | ||
| 728 | Self Dividing Numbers | C++ Python | O(n) | O(1) | Medium | ||
| 754 | Reach a Number | C++ Python | O(logn) | O(1) | Medium | ||
| 775 | Global and Local Inversions | C++ Python | O(n) | O(1) | Medium | ||
| 779 | K-th Symbol in Grammar | C++ Python | O(1) | O(1) | Medium | ||
| 780 | Reaching Points | C++ Python | O(log(max(m, n))) | O(1) | Hard | ||
| 781 | Rabbits in Forest | C++ Python | O(n) | O(n) | Medium | ||
| 782 | Transform to Chessboard | C++ Python | O(n^2) | O(n) | Hard |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 056 | Merge Intervals | C++ Python | O(nlogn) | O(1) | Hard | ||
| 057 | Insert Interval | C++ Python | O(n) | O(1) | Hard | ||
| 075 | Sort Colors | C++ Python | O(n) | O(1) | Medium | Tri Partition | |
| 088 | Merge Sorted Array | C++ Python | O(n) | O(1) | Easy | ||
| 147 | Insertion Sort List | C++ Python | O(n^2) | O(1) | Medium | ||
| 148 | Sort List | C++ Python | O(nlogn) | O(logn) | Medium | ||
| 164 | Maximum Gap | C++ Python | O(n) | O(n) | Hard | Tricky | |
| 179 | Largest Number | C++ Python | O(nlogn) | O(1) | Medium | ||
| 218 | The Skyline Problem | C++ Python | O(nlogn) | O(n) | Hard | Sort, BST | |
| 252 | Meeting Rooms | C++ Python | O(nlogn) | O(n) | Easy | 📖 | |
| 253 | Meeting Rooms II | C++ Python | O(nlogn) | O(n) | Medium | 📖 | |
| 274 | H-Index | C++ Python | O(n) | O(n) | Medium | Counting Sort | |
| 280 | Wiggle Sort | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 324 | Wiggle Sort II | C++ Python | O(n) on average | O(1) | Medium | variant of Sort Colors | Tri Partition |
| 347 | Top K Frequent Elements | C++ Python | O(n) | O(n) | Medium | Quick Select, Heap, Bucket Sort | |
| 406 | Queue Reconstruction by Height | C++ Python | O(n * sqrt(n)) | O(n) | Medium | Tricky | |
| 451 | Sort Characters By Frequency | C++ Python | O(n) | O(n) | Medium | ||
| 692 | Top K Frequent Words | C++ Python | O(n + klogk) on average | O(n) | Medium | Quick Select, Heap, Bucket Sort |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 019 | Remove Nth Node From End of List | C++ Python | O(n) | O(1) | Easy | ||
| 086 | Partition List | C++ Python | O(n) | O(1) | Medium | ||
| 141 | Linked List Cycle | C++ Python | O(n) | O(1) | Easy | ||
| 142 | Linked List Cycle II | C++ Python | O(n) | O(1) | Medium | ||
| 143 | Reorder List | C++ Python | O(n) | O(1) | Medium | ||
| 167 | Two Sum II - Input array is sorted | C++ Python | O(n) | O(1) | Medium | ||
| 259 | 3Sum Smaller | C++ Python | O(n^2) | O(1) | Medium | 📖, LintCode | |
| 283 | Move Zeroes | C++ Python | O(n) | O(1) | Easy | ||
| 287 | Find the Duplicate Number | C++ Python | O(n) | O(1) | Hard | Binary Search, Two Pointers | |
| 344 | Reverse String | C++ Python | O(n) | O(1) | Easy | ||
| 345 | Reverse Vowels of a String | C++ Python | O(n) | O(1) | Easy | ||
| 349 | Intersection of Two Arrays | C++ Python | O(m + n) | O(min(m, n)) | Easy | EPI | Hash, Binary Search |
| 350 | Intersection of Two Arrays II | C++ Python | O(m + n) | O(1) | Easy | EPI | Hash, Binary Search |
| 360 | Sort Transformed Array | C++ Python | O(n) | O(1) | Medium | 📖 | |
| 457 | Circular Array Loop | C++ Python | O(n) | O(1) | Medium | ||
| 567 | Permutation in String | C++ Python | O(n) | O(1) | Medium | ||
| 611 | Valid Triangle Number | C++ Python | O(n^2) | O(1) | Medium | ||
| 777 | Swap Adjacent in LR String | C++ Python | O(n) | O(1) | Medium |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 220 | Contains Duplicate III | C++ Python | O(nlogk) | O(k) | Medium | ||
| 230 | Kth Smallest Element in a BST | C++ Python | O(max(h, k)) | O(min(h, k)) | Medium | ||
| 235 | Lowest Common Ancestor of a Binary Search Tree | C++ Python | O(h) | O(1) | Easy | EPI | |
| 270 | Closest Binary Search Tree Value | C++ Python | O(h) | O(1) | Easy | 📖 | |
| 285 | Inorder Successor in BST | C++ Python | O(h) | O(1) | Medium | 📖 | |
| 352 | Data Stream as Disjoint Intervals | C++ Python | O(logn) | O(n) | Hard | ||
| 449 | Serialize and Deserialize BST | C++ Python | O(n) | O(h) | Medium | ||
| 450 | Delete Node in a BST | C++ Python | O(h) | O(h) | Medium | ||
| 530 | Minimum Absolute Difference in BST | C++ Python | O(n) | O(h) | Easy | ||
| 776 | Split BST | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 783 | Minimum Distance Between BST Nodes | C++ Python | O(n) | O(h) | Easy |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 102 | Binary Tree Level Order Traversal | C++ Python | O(n) | O(n) | Easy | ||
| 107 | Binary Tree Level Order Traversal II | Python | O(n) | O(n) | Easy | ||
| 103 | Binary Tree Zigzag Level Order Traversal | Python | O(n) | O(n) | Medium | ||
| 117 | Populating Next Right Pointers in Each Node II | Python | O(n) | O(1) | Hard | ||
| 127 | Word Ladder | Python | O(n * d) | O(d) | Medium | ||
| 130 | Surrounded Regions | C++ Python | O(m * n) | O(m + n) | Medium | ||
| 133 | Clone Graph | Python | O(n) | O(n) | Medium | ||
| 207 | Course Schedule | Python | O(|V| + |E|) | O(|E|) | Medium | Topological Sort | |
| 210 | Course Schedule II | Python | O(|V| + |E|) | O(|E|) | Medium | Topological Sort | |
| 261 | Graph Valid Tree | C++ Python | O(|V| + |E|) | O(|V| + |E|) | Medium | 📖 | |
| 269 | Alien Dictionary | C++ Python | O(n) | O(1) | Hard | 📖 | Topological Sort, BFS, DFS |
| 286 | Walls and Gates | C++ Python | O(m * n) | O(g) | Medium | 📖 | |
| 310 | Minimum Height Trees | C++ Python | O(n) | O(n) | Medium | ||
| 317 | Shortest Distance from All Buildings | C++ Python | O(k * m * n) | O(m * n) | Hard | 📖 | |
| 433 | Minimum Genetic Mutation | C++ Python | O(n * b) | O(b) | Medium | ||
| 444 | Sequence Reconstruction | C++ Python | O(n * s) | O(n) | Medium | 📖 | Topological Sort |
| 542 | 01 Matrix | C++ Python | O(m * n) | O(m * n) | Medium | DP | |
| 666 | Path Sum IV | C++ Python | O(n) | O(w) | Medium | 📖 | Topological Sort |
| 675 | Cut Off Trees for Golf Event | C++ Python | O(t * m * n) | O(m * n) | Hard | A* Search Algorithm |
|
| 742 | Closest Leaf in a Binary Tree | C++ Python | O(n) | O(n) | Medium | ||
| 743 | Network Delay Time | C++ Python | O(|E| + |V|log|V|) | O(|E| + |V|) | Medium | Dijkstra's algorithm |
|
| 752 | Open the Lock | C++ Python | O(k * n^k + d) | O(k * n^k + d) | Medium | ||
| 773 | Sliding Puzzle | C++ Python | O((m * n) * (m * n)!) | O((m * n) * (m * n)!) | Hard | A* Search Algorithm |
|
| 787 | Cheapest Flights Within K Stops | C++ Python | O(|E| + |V|log|V|) | O(|E| + |V|) | Medium | Dijkstra's algorithm |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 112 | Path Sum | Python | O(n) | O(h) | Easy | ||
| 113 | Path Sum II | Python | O(n) | O(h) | Medium | ||
| 199 | Binary Tree Right Side View | Python | O(n) | O(h) | Medium | ||
| 200 | Number of Islands | Python | O(m * n) | O(m * n) | Medium | ||
| 236 | Lowest Common Ancestor of a Binary Tree | C++ Python | O(n) | O(h) | Medium | EPI | |
| 247 | Strobogrammatic Number II | C++ Python | O(n^2 * 5^(n/2)) | O(n) | Medium | 📖 | |
| 250 | Count Univalue Subtrees | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 257 | Binary Tree Paths | C++ Python | O(n * h) | O(h) | Easy | ||
| 282 | Expression Add Operators | C++ Python | O(4^n) | O(n) | Hard | ||
| 301 | Remove Invalid Parentheses | C++ Python | O(C(n, c)) | O(c) | Hard | ||
| 329 | Longest Increasing Path in a Matrix | C++ Python | O(m * n) | O(m * n) | Hard | ||
| 332 | Reconstruct Itinerary | C++ Python | O(t! / (n1! * n2! * ... nk!)) | O(t) | Medium | ||
| 339 | Nested List Weight Sum | C++ Python | O(n) | O(h) | Easy | 📖 | |
| 364 | Nested List Weight Sum II | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 366 | Find Leaves of Binary Tree | C++ Python | O(n) | O(h) | Medium | 📖 | |
| 399 | Evaluate Division | C++ Python | O(q * |V|!) | O(e) | Medium | ||
| 417 | Pacific Atlantic Water Flow | C++ Python | O(m * n) | O(m * n) | Medium | ||
| 440 | K-th Smallest in Lexicographical Order | C++ Python | O(logn) | O(logn) | Hard | ||
| 464 | Can I Win | C++ Python | O(n!) | O(n) | Medium | ||
| 547 | Friend Circles | C++ Python | O(n^2) | O(n) | Medium | Union Find | |
| 582 | Kill Process | C++ Python | O(n) | O(n) | Medium | 📖 | DFS, BFS |
| 638 | Shopping Offers | C++ Python | O(n * 2^n) | O(n) | Medium | ||
| 690 | Employee Importance | C++ Python | O(n) | O(h) | Easy | DFS, BFS | |
| 694 | Number of Distinct Islands | C++ Python | O(m * n) | O(m * n) | Medium | 📖 | |
| 695 | Max Area of Island | C++ Python | O(m * n) | O(m * n) | Easy | ||
| 711 | Number of Distinct Islands II | C++ Python | O((m * n) * log(m * n)) | O(m * n) | Hard | 📖 | Hash |
| 733 | Max Area of Island | C++ Python | O(m * n) | O(m * n) | Easy | ||
| 749 | Contain Virus | C++ Python | O((m * n)^(4/3)) | O(m * n) | Hard | Simulation | |
| 753 | Cracking the Safe | C++ Python | O(k^n) | O(k^n) | Hard | de Bruijn sequences, Lyndon word |
|
| 756 | Pyramid Transition Matrix | C++ Python | O(a^b) | O(a^b) | Medium | ||
| 785 | Is Graph Bipartite? | C++ Python | O(|V| + |E|) | O(|V|) | Medium |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 017 | Letter Combinations of a Phone Number | Python | O(n * 4^n) | O(n) | Medium | ||
| 022 | Generate Parentheses | Python | O(4^n / n^(3/2)) | O(n) | Medium | ||
| 037 | Sudoku Solver | Python | O((9!)^9) | O(1) | Hard | ||
| 039 | Combination Sum | Python | O(k * n^k) | O(k) | Medium | ||
| 040 | Combination Sum II | Python | O(k * C(n, k)) | O(k) | Medium | ||
| 046 | Permutations | Python | O(n * n!) | O(n) | Medium | ||
| 047 | Permutations II | Python | O(n * n!) | O(n) | Medium | ||
| 051 | N-Queens | Python | O(n!) | O(n) | Hard | ||
| 052 | N-Queens-II | Python | O(n!) | O(n) | Hard | ||
| 077 | Combinations | Python | O(n!) | O(n) | Medium | ||
| 079 | Word Search | Python | O(m * n * l) | O(l) | Medium | ||
| 093 | Restore IP Addresses | Python | O(1) | O(1) | Medium | ||
| 078 | Subsets | C++ Python | O(n * 2^n) | O(1) | Medium | ||
| 090 | Subsets II | C++ Python | O(n * 2^n) | O(1) | Medium | ||
| 126 | Word Ladder II | Python | O(n * d) | O(d) | Hard | ||
| 131 | Palindrome Partitioning | Python | O(n^2) ~ O(2^n) | O(n^2) | Medium | ||
| 140 | Word Break II | C++ Python | O(n * l^2 + n * r) | O(n^2) | Hard | ||
| 212 | Word Search II | C++ Python | O(m * n * l) | O(l) | Hard | LintCode | Trie, DFS |
| 216 | Combination Sum III | C++ Python | O(k * C(n, k)) | O(k) | Medium | ||
| 254 | Factor Combinations | C++ Python | O(nlogn) | O(logn) | Medium | 📖 | |
| 267 | Palindrome Permutation II | C++ Python | O(n * n!) | O(n) | Medium | 📖 | |
| 291 | Word Pattern II | C++ Python | O(n * C(n - 1, c - 1)) | O(n + c) | Hard | 📖 | |
| 294 | Flip Game II | C++ Python | O(n + c^2) | O(c) | Medium | 📖 | DP, Hash |
| 320 | Generalized Abbreviation | C++ Python | O(n * 2^n) | O(n) | Medium | 📖 | |
| 425 | Word Squares | C++ Python | O(n^2 * n!) | O(n^2) | Hard | 📖 | |
| 526 | Beautiful Arrangement | C++ Python | O(n!) | O(n) | Medium | ||
| 676 | Implement Magic Dictionary | C++ Python | O(n) | O(d) | Medium | Trie, DFS | |
| 679 | 24 Game | C++ Python | O(1) | O(1) | Hard | DFS | |
| 698 | Partition to K Equal Sum Subsets | C++ Python | O(n * 2^n) | O(2^n) | Medium | DFS, DP, Memoization | |
| 718 | Maximum Length of Repeated Subarray | C++ Python | O(m * n) | O(min(m, n)) | Medium | DP, Hash, Binary Search | |
| 784 | Letter Case Permutation | C++ Python | O(n * 2^n) | O(1) | Easy |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 011 | Container With Most Water | C++ Python | O(n) | O(1) | Medium | ||
| 042 | Trapping Rain Water | C++ Python | O(n) | O(1) | Hard | Tricky | |
| 044 | Wildcard Matching | Python | O(m + n) | O(1) | Hard | Tricky | |
| 045 | Jump Game II | Python | O(n) | O(1) | Hard | ||
| 055 | Jump Game | Python | O(n) | O(1) | Medium | ||
| 122 | Best Time to Buy and Sell Stock II | Python | O(n) | O(1) | Easy | ||
| 134 | Gas Station | Python | O(n) | O(1) | Medium | ||
| 135 | Candy | C++ Python | O(n) | O(n) | Hard | ||
| 316 | Remove Duplicate Letters | C++ Python | O(n) | O(k) | Hard | Ascending Stack | |
| 321 | Create Maximum Number | C++ Python | O(k * (m + n + k)) ~ O(k * (m + n + k^2)) | O(m + n + k^2) | Hard | variant of Delete Digits | Greedy, DP |
| 330 | Patching Array | C++ Python | O(s + logn) | O(1) | Hard | ||
| 376 | Wiggle Subsequence | C++ Python | O(n) | O(1) | Medium | ||
| 392 | Is Subsequence | C++ Python | O(n) | O(1) | Medium | ||
| 397 | Integer Replacement | C++ Python | O(n) | O(1) | Medium | Math | |
| 402 | Remove K Digits | C++ Python | O(n) | O(n) | Medium | LintCode | |
| 435 | Non-overlapping Intervals | C++ Python | O(nlogn) | O(1) | Medium | Scan Line | |
| 452 | Minimum Number of Arrows to Burst Balloons | C++ Python | O(nlogn) | O(1) | Medium | ||
| 455 | Assign Cookies | C++ Python | O(nlogn) | O(1) | Easy | ||
| 621 | Task Scheduler | C++ Python | O(n) | O(1) | Medium | ||
| 630 | Course Schedule III | C++ Python | O(nlogn) | O(k) | Hard | ||
| 646 | Maximum Length of Pair Chain | C++ Python | O(nlogn) | O(1) | Medium | similar to Non-overlapping Intervals | Scan Line |
| 649 | Dota2 Senate | C++ Python | O(n) | O(n) | Medium | ||
| 659 | Split Array into Consecutive Subsequences | C++ Python | O(n) | O(1) | Medium | ||
| 738 | Monotone Increasing Digits | C++ Python | O(1) | O(1) | Medium | ||
| 757 | Set Intersection Size At Least Two | C++ Python | O(nlogn) | O(n) | Hard | ||
| 759 | Employee Free Time | C++ Python | O(m * logn) | O(n) | Hard | ||
| 763 | Partition Labels | C++ Python | O(n) | O(n) | Medium | ||
| 767 | Reorganize String | C++ Python | O(n) | O(1) | Medium |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 765 | Couples Holding Hands | C++ Python | O(n) | O(n) | Hard |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 587 | Erect the Fence | C++ Python | O(nlogn) | O(n) | Hard | Monotone Chain |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 146 | LRU Cache | C++ Python | O(1) | O(k) | Hard | ||
| 225 | Implement Stack using Queues | C++ Python | push: O(n), pop: O(1), top: O(1) | O(n) | Easy | ||
| 284 | Peeking Iterator | C++ Python | O(1) | O(1) | Medium | ||
| 348 | Design Tic-Tac-Toe | C++ Python | O(1) | O(n^2) | Medium | 📖 | |
| 353 | Design Snake Game | C++ Python | O(1) | O(s) | Medium | 📖 | Deque |
| 355 | Design Twitter | C++ Python | O(klogu) | O(t + f) | Medium | LintCode | Heap |
| 359 | Logger Rate Limiter | C++ Python | O(1), amortized | O(k) | Easy | 📖 | Deque |
| 362 | Design Hit Counter | C++ Python | O(1), amortized | O(k) | Medium | 📖 | Deque |
| 379 | Design Phone Directory | C++ Python | O(1) | O(n) | Medium | 📖 | |
| 380 | Insert Delete GetRandom O(1) | C++ Python | O(1) | O(n) | Hard | ||
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | C++ Python | O(1) | O(n) | Hard | ||
| 432 | All O`one Data Structure | C++ Python | O(1) | O(n) | Hard | ||
| 460 | LFU Cache | C++ Python | O(1) | O(k) | Hard | ||
| 535 | Encode and Decode TinyURL | C++ Python | O(1) | O(n) | Medium | ||
| 588 | Design In-Memory File System | C++ Python | ls: O(l + klogk) mkdir: O(l) addContentToFile: O(l + c) readContentFromFile: O(l + c) |
O(n + s) | Hard | 📖 | |
| 604 | Design Compressed String Iterator | C++ Python | O(1) | O(1) | Easy | 📖 | |
| 631 | Design Excel Sum Formula | C++ Python | set: O((r * c)^2) get: O(1) sum: O((r * c)^2) |
O(r * c) | Hard | 📖 | |
| 635 | Design Log Storage System | C++ Python | put: O(1) retrieve: O(n + dlogd) |
O(n) | Medium | 📖 | |
| 642 | Design Search Autocomplete System | C++ Python | O(p^2) | O(p * t + s) | Hard | 📖 | |
| 715 | Range Module | C++ Python | add: O(n) remove: O(n) query: O(logn) |
O(n) | Hard | ||
| 716 | Max Stack | C++ Python | push: O(logn) pop: O(logn) popMax: O(logn) top: O(1) peekMax: O(1) |
O(n) | Easy | ||
| 745 | Prefix and Suffix Search | C++ Python | ctor: O(w * l^2) search : O(p + s) |
O(t) | Hard | Trie |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 175 | Combine Two Tables | MySQL | O(m + n) | O(m + n) | Easy | ||
| 176 | Second Highest Salary | MySQL | O(n) | O(1) | Easy | ||
| 177 | Nth Highest Salary | MySQL | O(n^2) | O(n) | Medium | ||
| 178 | Rank Scores | MySQL | O(n^2) | O(n) | Medium | ||
| 180 | Consecutive Numbers | MySQL | O(n) | O(n) | Medium | ||
| 181 | Employees Earning More Than Their Managers | MySQL | O(n^2) | O(1) | Easy | ||
| 182 | Duplicate Emails | MySQL | O(n^2) | O(n) | Easy | ||
| 183 | Customers Who Never Order | MySQL | O(n^2) | O(1) | Easy | ||
| 184 | Department Highest Salary | MySQL | O(n^2) | O(n) | Medium | ||
| 185 | Department Top Three Salaries | MySQL | O(n^2) | O(n) | Hard | ||
| 196 | Delete Duplicate Emails | MySQL | O(n^2) | O(n) | Easy | ||
| 197 | Rising Temperature | MySQL | O(n^2) | O(n) | Easy | ||
| 262 | Trips and Users | MySQL | O((t * u) + tlogt) | O(t) | Hard |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 192 | Word Frequency | Shell | O(n) | O(k) | Medium | ||
| 193 | Valid Phone Numbers | Shell | O(n) | O(1) | Easy | ||
| 194 | Transpose File | Shell | O(n^2) | O(n^2) | Medium | ||
| 195 | Tenth Line | Shell | O(n) | O(1) | Easy |