Leetcode-Solutions
PYTHON
Array
Backtracking
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0017 | Letter Combinations of a Phone Number | Python | O(n * 4^n) | O(n) | Medium | ||
| 0022 | Generate Parentheses | Python | O(4^n / n^(3/2)) | O(n) | Medium | ||
| 0078 | Subsets | Python | O(n * 2^n) | O(1) | Medium | ||
| 0079 | Word Search | Python | O(m * n * 3^l) | O(l) | Medium | ||
| 0090 | Subsets II | Python | O(n * 2^n) | O(1) | Medium |
Binary Heap
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0703 | Kth Largest Element in a Stream | Python | O(nlogk) | O(k) | Easy | ||
| 1046 | Last Stone Weight | Python | O(nlogn) | O(n) | Easy |
Binary Search
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0033 | Search in Rotated Sorted Array | Python | O(logn) | O(1) | Medium | ||
| 0162 | Find Peak Element | Python | O(logn) | O(1) | Medium | ||
| 0034 | Search for a Range | Python | O(logn) | O(1) | Medium | ||
| 0035 | Search Insert Position | Python | O(logn) | O(1) | Easy | ||
| 0074 | Search a 2D Matrix | Python | O(logm + logn) | O(1) | Medium | ||
| 0153 | Find Minimum in Rotated Sorted Array | Python | O(logn) | O(1) | Medium | ||
| 0278 | First Bad Version | Python | O(logn) | O(1) | Easy | LintCode | |
| 0367 | Valid Perfect Square | Python | O(logn) | O(1) | Easy | ||
| 0374 | Guess Number Higher or Lower | Python | O(logn) | O(1) | Easy | ||
| 0658 | Find K Closest Elements | Python | O(logn + k) | O(1) | Medium | ||
| 0700 | Search in a Binary Search Tree | Python | O(logn) | O(logn) | Easy | ||
| 0702 | Search in a Sorted Array of Unknown Size | Python | O(logn) | O(logn) | Easy | ||
| 0875 | Koko Eating Bananas | Python | O(nlogr) | O(1) | Medium |
Binary Search Tree
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0230 | Kth Smallest Element in a BST | Python | O(max(h, k)) | O(min(h, k)) | Medium | ||
| 0235 | Lowest Common Ancestor of a Binary Search Tree | Python | O(h) | O(1) | Easy | EPI | |
| 0270 | Closest Binary Search Tree Value | Python | O(h) | O(1) | Easy | ||
| 0450 | Delete Node in a BST | Python | O(h) | O(h) | Medium |
Bit Manipulation
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0190 | Reverse Bits | Python | O(1) | O(1) | Easy | ||
| 0191 | Number of 1 Bits | Python | O(1) | O(1) | Easy | ||
| 0268 | Missing Number | Python | O(n) | O(1) | Medium | ||
| 0342 | Power of Four | Python | O(1) | O(1) | Easy | ||
| 0389 | Find the Difference | Python | O(n) | O(1) | Easy |
Breadth-First Search
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0102 | Binary Tree Level Order Traversal | Python | O(n) | O(n) | Medium | ||
| 0103 | Binary Tree Zigzag Level Order Traversal | Python | O(n) | O(n) | Medium | ||
| 0133 | Clone Graph | Python | O(n) | O(n) | Medium | ||
| 0286 | Walls and Gates | Python | O(m * n) | O(g) | Medium | 🔒 | |
| 0339 | Nested List Weight Sum | Python | O(N) | O(N) | Medium | ||
| 0364 | Nested List Weight Sum II | Python | O(N) | O(N) | Medium | ||
| 0490 | The Maze | Python | O(max(r, c) * w) | O(w) | Medium | ||
| 0994 | Rotting Oranges | Python | O(m * n) | O(m * n) | Medium | ||
| 9997 | Zombie in Matrix | Python | O(m * n) | O(m * n) | Medium |
Depth-First Search
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0112 | Path Sum | Python | O(n) | O(h) | Easy | ||
| 0113 | Path Sum II | Python | O(n) | O(h) | Medium | ||
| 0199 | Binary Tree Right Side View | Python | O(n) | O(h) | Medium | ||
| 0200 | Number of Islands | Python | O(m * n) | O(m * n) | Medium | ||
| 0207 | Course Schedule | Python | O(|V| + |E|) | O(|E|) | Medium | Topological Sort | |
| 0210 | Course Schedule II | Python | O(|V| + |E|) | O(|E|) | Medium | Topological Sort | |
| 0236 | Lowest Common Ancestor of a Binary Tree | Python | O(n) | O(h) | Medium | EPI | |
| 0250 | Count Univalue Subtrees | Python | O(n) | O(h) | Medium | 🔒 | |
| 0257 | Binary Tree Paths | Python | O(n * h) | O(h) | Easy |
Design
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0146 | LRU Cache | Python | O(1) | O(k) | Hard | ||
| 0346 | Moving Average from Data Stream | Python | O(N) | O(M) | Easy | ||
| 1348 | Tweet Counts Per Frequency | Python | add: O(logn) query: O(c) |
O(n) | Medium | ||
| 1570 | Dot Product of Two Sparse Vectors | Python | ctor: O(n) dot_product: O(min(n, m)) |
O(n) | Medium | 🔒 |
Dynamic Programming
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0053 | Maximum Subarray | Python | O(n) | O(1) | Medium | ||
| 0062 | Unique Paths | Python | O(m * n) | O(m + n) | Medium | ||
| 0063 | Unique Paths II | Python | O(m * n) | O(m + n) | Medium | ||
| 0070 | Climbing Stairs | Python | O(logn) | O(1) | Easy | Matrix Exponentiation | |
| 0096 | Unique Binary Search Trees | Python | O(n) | O(1) | Medium | Math | |
| 0123 | Best Time to Buy and Sell Stock III | Python | O(n) | O(1) | Hard | ||
| 0152 | Maximum Product Subarray | Python | O(n) | O(1) | Medium | ||
| 0198 | House Robber | Python | O(n) | O(1) | Medium | ||
| 0213 | House Robber II | Python | O(n) | O(1) | Medium | ||
| 0303 | Range Sum Query - Immutable | Python | ctor: O(n), lookup: O(1) | O(n) | Easy | ||
| 0322 | Coin Change | Python | O(n * k) | O(k) | Medium | ||
| 0718 | Maximum Length of Repeated Subarray | Python | O(m * n) | O(min(m, n)) | Medium | DP, Hash, Binary Search |
Greedy
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0055 | Jump Game | Python | O(n) | O(1) | Medium | ||
| 0122 | Best Time to Buy and Sell Stock II | Python | O(n) | O(1) | Easy | ||
| 0435 | Non-overlapping Intervals | Python | O(nlogn) | O(1) | Medium | Line Sweep | |
| 0621 | Task Scheduler | Python | O(n) | O(1) | Medium | ||
| 0763 | Partition Labels | Python | O(n) | O(n) | Medium | ||
| 1249 | Minimum Remove to Make Valid Parentheses | Python | O(n) | O(1) | Medium | Stack | |
| 1710 | Maximum Units on a Truck | Python | O(nlogn) | O(1) | Easy |
Hash Table
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0001 | Two Sum | Python | O(n) | O(n) | Easy | ||
| 0003 | Longest Substring Without Repeating Characters | Python | O(n) | O(1) | Medium | ||
| 0036 | Valid Sudoku | Python | O(9^2) | O(9) | Easy | ||
| 0049 | Group Anagrams | Python | O(n * glogg) | O(n) | Medium | ||
| 0205 | Isomorphic Strings | Python | O(n) | O(1) | Easy | ||
| 0217 | Contains Duplicate | Python | O(n) | O(n) | Easy | ||
| 0249 | Group Shifted Strings | Python | O(nlogn) | O(n) | Medium | 🔒 | |
| 0387 | First Unique Character in a String | Python | O(n) | O(n) | Easy | ||
| 0438 | Find All Anagrams in a String | Python | O(n) | O(1) | Easy | ||
| 0523 | Continuous Subarray Sum | Python | O(n) | O(k) | Medium | ||
| 0560 | Subarray Sum Equals K | Python | O(n) | O(n) | Medium | ||
| 0599 | Minimum Index Sum of Two Lists | Python | O((m + n) * l) | O(m * l) | Easy | ||
| 0811 | Subdomain Visit Count | Python | O(n) | O(n) | Medium | ||
| 1152 | Analyze User Website Visit Pattern | Python | O(n^3) | O(n^3) | Medium | 🔒 | Hash |
| 1817 | Finding the Users Active Minutes | Python | O(n) | O(n) | Medium |
Linked List
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0002 | Add Two Numbers | Python | O(n) | O(1) | Medium | ||
| 0021 | Merge Two Sorted Lists | Python | O(n) | O(1) | Easy | ||
| 0024 | Swap Nodes in Pairs | Python | O(n) | O(1) | Easy | ||
| 0138 | Copy List with Random Pointer | Python | O(n) | O(1) | Medium | ||
| 0206 | Reverse Linked List | Python | O(n) | O(1) | Easy | ||
| 0986 | Interval List Intersections | Python | O(m + n) | O(1) | Medium |
Math
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0007 | Reverse Integer | Python | O(1) | O(1) | Easy | ||
| 0013 | Roman to Integer | Python | O(n) | O(1) | Easy | ||
| 0326 | Power of Three | Python | O(1) | O(1) | Easy | ||
| 0338 | Counting Bits | Python | O(n) | O(n) | Medium | ||
| 1492 | The kth Factor of n | Python | O(sqrt(n)) | O(1) | Medium | ||
| 1904 | The Number of Full Rounds You Have Played | Python | O(1) | O(1) | Medium |
Recursion
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0046 | Permutations | Python | O(n * n!) | O(n) | Medium | ||
| 0047 | Permutations II | Python | O(n * n!) | O(n) | Medium | ||
| 0095 | Unique Binary Search Trees II | Python | O(4^n / n^(3/2) | O(4^n / n^(3/2) | Medium | ||
| 0098 | Validate Binary Search Tree | Python | O(n) | O(1) | Medium | ||
| 0100 | Same Tree | Python | O(n) | O(h) | Easy | ||
| 0104 | Maximum Depth of Binary Tree | Python | O(n) | O(h) | Easy | Blind 75 | |
| 0110 | Balanced Binary Tree | Python | O(n) | O(h) | Easy | ||
| 0404 | Sum of Left Leaves | Python | O(n) | O(h) | Easy | ||
| 0437 | Path Sum III | Python](./Python/path-sum-iii.py) | O(n) | O(h) | Easy |
Sort
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0056 | Merge Intervals | Python | O(nlogn) | O(1) | Medium | ||
| 0057 | Insert Interval | Python | O(n) | O(1) | Medium | ||
| 0075 | Sort Colors | Python | O(n) | O(1) | Medium | Tri Partition | |
| 0088 | Merge Sorted Array | Python | O(n) | O(1) | Easy | ||
| 0252 | Meeting Rooms | Python | O(nlogn) | O(n) | Easy | 🔒 | |
| 0253 | Meeting Rooms II | Python | O(nlogn) | O(n) | Medium | 🔒 | |
| 0274 | H-Index | Python | O(n) | O(n) | Medium | Counting Sort | |
| 0347 | Top K Frequent Elements | Python | O(n) | O(n) | Medium | Quick Select, Heap, Bucket Sort | |
| 0692 | Top K Frequent Words | Python | O(n + klogk) on average | O(n) | Medium | Quick Select, Heap, Bucket Sort | |
| 0969 | Pancake Sorting | Python | O(n^2) | O(l) | Medium | ||
| 0973 | K Closest Points to Origin | Python | O(n) on average | O(1) | Medium | Quick Select, Heap | |
| 1094 | Car Pooling | Python | O(nlogn) | O(n) | Medium | variant of Meeting Rooms II | |
| 9999 | Top K Frequently Mentioned Keywords | Python | O(n) on average | O(1) | Medium | Quick Select, Heap |
Stack
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0020 | Valid Parentheses | Python | O(n) | O(n) | Easy | ||
| 0071 | Simplify Path | Python | O(n) | O(n) | Medium | ||
| 0101 | Symmetric Tree | Python | O(n) | O(h) | Easy | ||
| 0150 | Evaluate Reverse Polish Notation | Python | O(n) | O(n) | Medium | ||
| 0682 | Baseball Game | Python | O(n) | O(n) | Easy | ||
| 0739 | Daily Temperatures | Python | O(n) | O(n) | Medium |
String
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0005 | Longest Palindromic Substring | Python | O(n) | O(n) | Medium | Blind75 | |
| 0008 | String to Integer (atoi) | Python | O(n) | O(1) | Medium | ||
| 0014 | Longest Common Prefix | Python | O(n * k) | O(1) | Easy | ||
| 0028 | Implement strStr() | Python | O(n + k) | O(k) | Easy | KMP Algorithm |
|
| 0038 | Count and Say | Python | O(n * 2^n) | O(2^n) | Easy | ||
| 0043 | Multiply Strings | Python | O(m * n) | O(m + n) | Medium | ||
| 0067 | Add Binary | Python | O(n) | O(1) | Easy | ||
| 0076 | Minimum Window Substring | Python | O(n) | O(k) | Hard | ||
| 0125 | Valid Palindrome | Python | O(n) | O(1) | Easy | Blind 75 | |
| 0151 | Reverse Words in a String | Python | O(n) | O(1) | Medium | ||
| 0271 | Encode and Decode Strings | Python | O(n) | O(1) | Medium | 🔒 | |
| 0383 | Ransom Note | Python | O(n) | O(1) | Easy | ||
| 0415 | Add Strings | Python | O(n) | O(1) | Easy | ||
| 0468 | Validate IP Address | Python | O(1) | O(1) | Medium | ||
| 0557 | Reverse Words in a String III | Python | O(n) | O(1) | Easy | ||
| 0647 | Palindromic Substrings | Python | O(n) | O(n) | Medium | ||
| 0680 | Valid Palindrome II | Python | O(n) | O(1) | Easy | ||
| 0819 | Most Common Word | Python | O(m + n) | O(m + n) | Easy | ||
| 0953 | Verifying an Alien Dictionary | Python | O(n * l) | O(1) | Easy | ||
| 1347 | Minimum Number of Steps to Make Two Strings Anagram | Python | O(n) | O(1) | Medium |
Tree
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0094 | Binary Tree Inorder Traversal | Python | O(n) | O(1) | Medium | Morris Traversal |
|
| 0144 | Binary Tree Preorder Traversal | Python | O(n) | O(1) | Medium | Morris Traversal |
|
| 0145 | Binary Tree Postorder Traversal | Python | O(n) | O(1) | Hard | Morris Traversal |
|
| 0226 | Invert Binary Tree | Python | O(n) | O(h), O(w) | Easy | ||
| 0543 | Diameter of Binary Tree | Python | O(n) | O(h) | Easy | ||
| 0572 | Subtree of Another Tree | Python | O(m * n) | O(h) | Easy | ||
| 0938 | Range Sum of BST | Python | O(n) | O(h) | Easy | DFS | |
| 0987 | Vertical Order Traversal of a Binary Tree | Python | O(nlogn) | O(n) | Medium | DFS |
Two Pointers
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0019 | Remove Nth Node From End of List | Python | O(n) | O(1) | Easy | ||
| 0143 | Reorder List | Python | O(n) | O(1) | Medium | ||
| 0167 | Two Sum II - Input array is sorted | Python | O(n) | O(1) | Medium | ||
| 0209 | Minimum Size Subarray Sum | Python | O(n) | O(1) | Medium | Binary Search, Sliding Window | |
| 0283 | Move Zeroes | Python | O(n) | O(1) | Easy | ||
| 0287 | Find the Duplicate Number | Python | O(n) | O(1) | Medium | Binary Search, Two Pointers | |
| 0344 | Reverse String | Python | O(n) | O(1) | Easy | ||
| 0345 | Reverse Vowels of a String | Python | O(n) | O(1) | Easy | ||
| 0349 | Intersection of Two Arrays | Python | O(m + n) | O(min(m, n)) | Easy | EPI | Hash, Binary Search |
| 0424 | Longest Repeating Character Replacement | Python | O(n) | O(1) | Medium | Sliding Window | |
| 0350 | Intersection of Two Arrays II | Python | O(m + n) | O(1) | Easy | ||
| 0567 | Permutation in String | Python | O(n) | O(1) | Medium | ||
| 1248 | Count Number of Nice Subarrays | Python | O(n) | O(k) | Medium | variant of Subarrays with K Different Integers | Two Pointers, Sliding Window |
| 1493 | Longest Subarray of 1's After Deleting One Element | Python | O(n) | O(1) | Medium | Sliding Window | |
| 1604 | Alert Using Same Key-Card Three or More Times in a One Hour Period | Python | O(nlogn) | O(n) | Medium | Two Pointers, Sliding Window |