LeetCode
![Travis](https://camo.githubusercontent.com/6e4ec12390d978090653b9f7cb54af6e1aacc30f240b3a1a1b27e4d373348045/68747470733a2f2f7472617669732d63692e6f72672f6b616d79753130342f4c656574436f64652e7376673f6272616e63683d6d6173746572)
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: "๐" means you need to subscribe to LeetCode premium membership for the access to premium questions.)
Algorithms
- 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
- Simulation
- Design
Database
Shell
Reference
- C++
- Python
Bit Manipulation
Array
String
Linked List
Stack
# | 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 | ๐ | |
272 | Closest Binary Search Tree Value II | C++ Python | O(h + k) | O(h) | Hard | ๐ | |
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 | ๐ | 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 | ๐ | |
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 | ||
853 | Car Fleet | C++ Python | O(nlogn) | O(n) | Medium | ||
856 | Score of Parentheses | C++ Python | O(n) | O(1) | Medium | ||
872 | Leaf-Similar Trees | C++ Python | O(n) | O(h) | Easy | ||
895 | Maximum Frequency Stack | C++ Python | O(1) | O(n) | Hard | Hash |
Queue
# | 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 | ๐ | |
346 | Moving Average from Data Stream | C++ Python | O(1) | O(w) | Easy | ๐ | |
862 | Shortest Subarray with Sum at Least K | C++ Python | O(n) | O(n) | Hard |
Heap
# | 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 | ๐ | 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 | ||
846 | Hand of Straights | C++ Python | O(nlogn) | O(n) | Medium | ||
855 | Exam Room | C++ Python | seat: O(logn) leave: O(logn) |
O(n) | Medium | BST, Hash | |
857 | Minimum Cost to Hire K Workers | C++ Python | O(nlogn) | O(n) | Hard | Sort | |
871 | Minimum Number of Refueling Stops | C++ Python | O(nlogn) | O(n) | Hard | Sort |
Tree
# | 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 | ๐ | 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 | ๐ | |
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 | ๐ | |
548 | Split Array with Equal Sum | C++ Python | O(n^2) | O(n) | Medium | ๐ | |
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 | ๐ | 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 | |
814 | Binary Tree Pruning | C++ Python | O(n) | O(h) | Medium | DFS | |
850 | Rectangle Area II | C++ Python | O(nlogn) | O(n) | Hard | Segment Tree | |
863 | All Nodes Distance K in Binary Tree | C++ Python | O(n) | O(n) | Medium | DFS + BFS | |
866 | Smallest Subtree with all the Deepest Nodes | C++ Python | O(n) | O(h) | Medium | DFS | |
889 | Construct Binary Tree from Preorder and Postorder Traversal | C++ Python | O(n) | O(h) | Medium | DFS, stack |
Hash Table
Math
Sort
# | 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 | ๐ | |
253 | Meeting Rooms II | C++ Python | O(nlogn) | O(n) | Medium | ๐ | |
274 | H-Index | C++ Python | O(n) | O(n) | Medium | Counting Sort | |
280 | Wiggle Sort | C++ Python | O(n) | O(1) | Medium | ๐ | |
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 |
Two Pointers
# | 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 | ๐, 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 | ๐ | |
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 | ||
826 | Most Profit Assigning Work | C++ Python | O(mlogm + nlogn) | O(n) | Medium | ||
828 | Unique Letter String | C++ Python | O(n) | O(1) | Hard | ||
844 | Backspace String Compare | C++ Python | O(m + n) | O(1) | Easy | ||
876 | Middle of the Linked List | C++ Python | O(n) | O(1) | Easy |
Recursion
Binary Search
Binary Search Tree
# | 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 | ๐ | |
285 | Inorder Successor in BST | C++ Python | O(h) | O(1) | Medium | ๐ | |
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 | ๐ | |
783 | Minimum Distance Between BST Nodes | C++ Python | O(n) | O(h) | Easy |
Breadth-First Search
# | 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 | ๐ | |
269 | Alien Dictionary | C++ Python | O(n) | O(1) | Hard | ๐ | Topological Sort, BFS, DFS |
286 | Walls and Gates | C++ Python | O(m * n) | O(g) | Medium | ๐ | |
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 | ๐ | |
433 | Minimum Genetic Mutation | C++ Python | O(n * b) | O(b) | Medium | ||
444 | Sequence Reconstruction | C++ Python | O(n * s) | O(n) | Medium | ๐ | 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 | ๐ | 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| * log|V|) | O(|E|) | 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| * log|V|) | O(|E|) | Medium | Dijkstra's algorithm |
|
815 | Bus Routes | C++ Python | O(|E| + |V|) | O(|E| + |V|) | Hard | ||
854 | K-Similar Strings | C++ Python | O(n * n!/(c_a!*...*c_z!)) | O(n * n!/(c_a!*...*c_z!)) | Hard | ||
865 | Shortest Path to Get All Keys | C++ Python | O(k * r * c + k^3*2^k) | O(k*2^k) | Hard | Dijkstra's algorithm |
|
882 | Reachable Nodes In Subdivided Graph | C++ Python | O(|E| * log|V|) | O(|E|) | Hard | Dijkstra's algorithm |
|
886 | Possible Bipartition | C++ Python | O(|V| + |E|) | O(|V| + |E|) | Medium |
Depth-First Search
# | 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 | ๐ | |
250 | Count Univalue Subtrees | C++ Python | O(n) | O(h) | Medium | ๐ | |
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 | ๐ | |
364 | Nested List Weight Sum II | C++ Python | O(n) | O(h) | Medium | ๐ | |
366 | Find Leaves of Binary Tree | C++ Python | O(n) | O(h) | Medium | ๐ | |
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 | ||
515 | Find Largest Value in Each Tree Row | C++ Python | O(n) | O(h) | Medium | ||
547 | Friend Circles | C++ Python | O(n^2) | O(n) | Medium | Union Find | |
582 | Kill Process | C++ Python | O(n) | O(n) | Medium | ๐ | 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 | ๐ | |
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 | ๐ | 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 | ||
797 | All Paths From Source to Target | C++ Python | O(p + r * n) | O(n) | Medium | ||
802 | Find Eventual Safe States | C++ Python | O(|V| + |E|) | O(|V|) | Medium | ||
827 | Making A Large Island | C++ Python | O(n^2) | O(n^2) | Hard | ||
834 | Sum of Distances in Tree | C++ Python | O(n) | O(n) | Hard | ||
841 | Keys and Rooms | C++ Python | O(n!) | O(n) | Medium | ||
851 | Loud and Rich | C++ Python | O(q + r) | O(q + r) | Medium |
Backtracking
# | 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(O(k * C(n, k))) | O(k) | 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 | ๐ | |
267 | Palindrome Permutation II | C++ Python | O(n * n!) | O(n) | Medium | ๐ | |
291 | Word Pattern II | C++ Python | O(n * C(n - 1, c - 1)) | O(n + c) | Hard | ๐ | |
294 | Flip Game II | C++ Python | O(n + c^2) | O(c) | Medium | ๐ | DP, Hash |
320 | Generalized Abbreviation | C++ Python | O(n * 2^n) | O(n) | Medium | ๐ | |
425 | Word Squares | C++ Python | O(n^2 * n!) | O(n^2) | Hard | ๐ | |
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 |
Dynamic Programming
# | Title | Solution | Time | Space | Difficulty | Tag | Note |
---|---|---|---|---|---|---|---|
010 | Regular Expression Matching | Python | O(m * n) | O(n) | Hard | ||
053 | Maximum Subarray | Python | O(n) | O(1) | Medium | ||
062 | Unique Paths | Python | O(m * n) | O(m + n) | Medium | ||
063 | Unique Paths II | Python | O(m * n) | O(m + n) | Medium | ||
064 | Minimum Path Sum | Python | O(m * n) | O(m + n) | Medium | ||
070 | Climbing Stairs | Python | O(n) | O(1) | Easy | ||
072 | Edit Distance | Python | O(m * n) | O(m + n) | Hard | ||
087 | Scramble String | Python | O(n^4) | O(n^3) | Hard | ||
091 | Decode Ways | C++ Python | O(n) | O(1) | Medium | ||
096 | Unique Binary Search Trees | Python | O(n) | O(1) | Medium | Math | |
097 | Interleaving String | Python | O(m * n) | O(m + n) | Hard | ||
115 | Distinct Subsequences | Python | O(n^2) | O(n) | Hard | ||
120 | Triangle | Python | O(m * n) | O(n) | Medium | ||
123 | Best Time to Buy and Sell Stock III | Python | O(n) | O(1) | Hard | ||
132 | Palindrome Partitioning II | Python | O(n^2) | O(n^2) | Hard | ||
139 | Word Break | C++ Python | O(n * l^2) | O(n) | Medium | ||
152 | Maximum Product Subarray | Python | O(n) | O(1) | Medium | ||
174 | Dungeon Game | Python | O(m * n) | O(m + n) | Hard | ||
188 | Best Time to Buy and Sell Stock IV | Python | O(k * n) | O(k) | Hard | ||
198 | House Robber | Python | O(n) | O(1) | Easy | ||
213 | House Robber II | C++ Python | O(n) | O(1) | Medium | ||
221 | Maximal Square | C++ Python | O(n^2) | O(n) | Medium | EPI | |
256 | Paint House | C++ Python | O(n) | O(1) | Medium | ๐ | |
265 | Paint House II | C++ Python | O(n * k) | O(k) | Hard | ๐ | |
276 | Paint Fence | C++ Python | O(n) | O(1) | Easy | ๐ | |
279 | Perfect Squares | C++ Python | O(n * sqrt(n)) | O(n) | Medium | Hash | |
303 | Range Sum Query - Immutable | C++ Python | ctor: O(n), lookup: O(1) | O(n) | Easy | ||
304 | Range Sum Query 2D - Immutable | C++ Python | ctor: O(m * n), lookup: O(1) | O(m * n) | Medium | ||
309 | Best Time to Buy and Sell Stock with Cooldown | C++ Python | O(n) | O(1) | Medium | ||
312 | Burst Balloons | C++ Python | O(n^3) | O(n^2) | Hard | ||
322 | Coin Change | C++ Python | O(n * k) | O(k) | Medium | ||
351 | Android Unlock Patterns | C++ Python | O(9^2 * 2^9) | O(9 * 2^9) | Medium | ๐ | Backtracking |
357 | Count Numbers with Unique Digits | C++ Python | O(n) | O(1) | Medium | Backtracking, Math | |
361 | Bomb Enemy | C++ Python | O(m * n) | O(m * n) | Medium | ๐ | |
368 | Largest Divisible Subset | C++ Python | O(n^2) | O(n) | Medium | ||
375 | Guess Number Higher or Lower II | C++ Python | O(n^2) | O(n^2) | Medium | ||
377 | Combination Sum IV | C++ Python | O(nlogn + n * t) | O(t) | Medium | ||
403 | Frog Jump | C++ Python | O(n) | O(n) ~ O(n^2) | Hard | ||
416 | Partition Equal Subset Sum | C++ Python | O(n * s) | O(s) | Medium | ||
418 | Sentence Screen Fitting | C++ Python | O(r + n * c) | O(n) | Medium | ๐ | |
446 | Arithmetic Slices II - Subsequence | C++ Python | O(n^2) | O(n * d) | Hard | ||
465 | Optimal Account Balancing | C++ Python | O(n * 2^n) | O(n * 2^n) | Hard | ๐ | |
466 | Count The Repetitions | C++ Python | O(s1 * min(s2, n1)) | O(s2) | Hard | ||
467 | Unique Substrings in Wraparound String | C++ Python | O(n) | O(1) | Medium | ||
471 | Encode String with Shortest Length | C++ Python | O(n^3) on average | O(n^2) | Medium | ๐ | |
472 | Concatenated Words | C++ Python | O(n * l^2) | O(n * l) | Medium | ||
474 | Ones and Zeroes | C++ Python | O(s * m * n) | O(m * n) | Medium | ||
486 | Predict the Winner | C++ Python | O(n^2) | O(n) | Medium | ||
514 | Freedom Trail | C++ Python | O(k) ~ O(k * r^2) | O(r) | Hard | ||
516 | Longest Palindromic Subsequence | C++ Python | O(n^2) | O(n) | Medium | ||
546 | Remove Boxes | C++ Python | O(n^3) ~ O(n^4) | O(n^3) | Hard | ||
552 | Student Attendance Record II | C++ Python | O(n) | O(1) | Hard | ||
562 | Longest Line of Consecutive One in Matrix | C++ Python | O(m * n) | O(n) | Medium | ๐ | |
568 | Maximum Vacation Days | C++ Python | O(n^2 * k) | O(k) | Hard | ๐ | |
576 | Out of Boundary Paths | C++ Python | O(N * m * n) | O(m * n) | Medium | ||
583 | Delete Operation for Two Strings | C++ Python | O(m * n) | O(n) | Medium | ||
600 | Non-negative Integers without Consecutive Ones | C++ Python | O(1) | O(1) | Hard | ||
629 | K Inverse Pairs Array | C++ Python | O(n * k) | O(k) | Hard | ||
639 | Decode Ways II | C++ Python | O(n) | O(1) | Hard | ||
650 | 2 Keys Keyboard | C++ Python | O(sqrt(n)) | O(1) | Medium | ||
656 | Coin Path | C++ Python | O(n * B) | O(n) | Hard | ๐ | |
664 | Strange Printer | C++ Python | O(n^3) | O(n^2) | Hard | ||
673 | Number of Longest Increasing Subsequence | C++ Python | O(n^2) | O(n) | Medium | ||
688 | Knight Probability in Chessboard | C++ Python | O(k * n^2) | O(n^2) | Medium | ||
689 | Maximum Sum of 3 Non-Overlapping Subarrays | C++ Python | O(n) | O(n) | Hard | ||
691 | Stickers to Spell Word | C++ Python | O(T * S^T) | O(T * S^T) | Hard | Backtracking, Memoization | |
712 | Minimum ASCII Delete Sum for Two Strings | C++ Python | O(m * n) | O(n) | Medium | ||
714 | Best Time to Buy and Sell Stock with Transaction Fee | C++ Python | O(n) | O(1) | Medium | ||
727 | Minimum Window Subsequence | C++ Python | O(s * t) | O(s) | Hard | ๐ | |
730 | Count Different Palindromic Subsequences | C++ Python | O(n^2) | O(n) | Hard | ||
740 | Delete and Earn | C++ Python | O(n) | O(1) | Medium | ||
741 | Cherry Pickup | C++ Python | O(n^3) | O(n^2) | Hard | ||
746 | Min Cost Climbing Stairs | C++ Python | O(n) | O(1) | Easy | ||
750 | Number Of Corner Rectangles | C++ Python | O(n * m^2) | O(n * m) | Medium | ||
764 | Largest Plus Sign | C++ Python | O(n^2) | O(n^2) | Medium | ||
788 | Rotated Digits | C++ Python | O(logn) | O(logn) | Easy | Memoization | |
790 | Domino and Tromino Tiling | C++ Python | O(logn) | O(logn) | Medium | Matrix Exponentiation | |
799 | Champagne Tower | C++ Python | O(n^2) | O(n) | Medium | ||
801 | Minimum Swaps To Make Sequences Increasing | C++ Python | O(n) | O(1) | Medium | ||
805 | Split Array With Same Average | C++ Python | O(n^4) | O(n^3) | Hard | ||
808 | Soup Servings | C++ Python | O(1) | O(1) | Medium | Memoization | |
813 | Largest Sum of Averages | C++ Python | O(k * n^2) | O(n) | Medium | ||
818 | Race Car | C++ Python | O(nlogn) | O(n) | Hard | ||
823 | Binary Trees With Factors | C++ Python | O(n^2) | O(n) | Medium | ||
837 | New 21 Game | C++ Python | O(n) | O(n) | Medium | ||
838 | Push Dominoes | C++ Python | O(n) | O(n) | Medium | ||
847 | Shortest Path Visiting All Nodes | C++ Python | O(n *2^n) | O(n * 2^n) | Hard | BFS | |
877 | Stone Game | C++ Python | O(n^2) | O(n) | Medium | variant of Predict the Winner | |
879 | Profitable Schemes | C++ Python | O(n * p * g) | O(p * g) |
Greedy
# | 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 | Line Sweep | |
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 | Line Sweep |
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 | ||
798 | Smallest Rotation with Highest Score | C++ Python | O(n) | O(1) | Hard | ||
843 | Guess the Word | C++ Python | O(n^2) | O(n) | Hard | MinMax | |
861 | Score After Flipping Matrix | C++ Python | O(r * c) | O(1) | Medium | ||
870 | Advantage Shuffle | C++ Python | O(nlogn) | O(n) | Medium | ||
881 | Boats to Save People | C++ Python | O(nlogn) | O(n) | Medium |
Graph
# | Title | Solution | Time | Space | Difficulty | Tag | Note |
---|---|---|---|---|---|---|---|
765 | Couples Holding Hands | C++ Python | O(n) | O(n) | Hard |
Geometry
# | Title | Solution | Time | Space | Difficulty | Tag | Note |
---|---|---|---|---|---|---|---|
587 | Erect the Fence | C++ Python | O(nlogn) | O(n) | Hard | Monotone Chain |
|
892 | Surface Area of 3D Shapes | C++ Python | O(n^2) | O(1) | Easy |
Simulation
# | Title | Solution | Time | Space | Difficulty | Tag | Note |
---|---|---|---|---|---|---|---|
874 | Walking Robot Simulation | C++ Python | O(n + k) | O(k) | Easy |
Design
# | 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 | ๐ | |
353 | Design Snake Game | C++ Python | O(1) | O(s) | Medium | ๐ | 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 | ๐ | Deque |
362 | Design Hit Counter | C++ Python | O(1), amortized | O(k) | Medium | ๐ | Deque |
379 | Design Phone Directory | C++ Python | O(1) | O(n) | Medium | ๐ | |
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 | ๐ | |
604 | Design Compressed String Iterator | C++ Python | O(1) | O(1) | Easy | ๐ | |
631 | Design Excel Sum Formula | C++ Python | set: O((r * c)^2) get: O(1) sum: O((r * c)^2) |
O(r * c) | Hard | ๐ | |
635 | Design Log Storage System | C++ Python | put: O(1) retrieve: O(n + dlogd) |
O(n) | Medium | ๐ | |
642 | Design Search Autocomplete System | C++ Python | O(p^2) | O(p * t + s) | Hard | ๐ | |
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 |
SQL
# | 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 |
Shell Script
# | 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 |