Solutions with code and explanations to leetcode problems I have worked on
| Number | Category | Problem name | Code | Whiteboard |
|---|---|---|---|---|
| 1 | Dictionary/Misc | Two sum | python | explanation |
| 2 | Linked List, Recursion | Add two numbers | python | explanation |
| 3 | Sliding Window | Longest substring without repeating characters | python | explanation |
| 5 | DP | Longest palindroming substring | python | explanation |
| 14 | String | Longest common prefix | python | explanation |
| 16 | Sort, Two Pointers | 3 sum closest | python | explanation |
| 17 | Recursion | Letter combinations of phone numbers | python | explanation |
| 18 | Strings | 4Sum | python | explanation |
| 19 | Linked List | Remove Nth node from end of list | python | explanation |
| 21 | Linked List | Merge two sorted lists | python | explanation |
| 22 | Recursion/Backtracking | Generate parantheses | python | explanation |
| 27 | Two Pointers | Remove element | python | explanation |
| 33 | Binary Search | Search in rotated sorted array | python | explanation |
| 34 | Binary Search | Find first last position in sorted array | python | explanation |
| 38 | String | Count and say | python | explanation |
| 41 | Array | First missing positive | python | explanation |
| 56 | Sorting, Queue | Merge intervals | python | explanation |
| 60 | Misc | Permutation sequence | python | explanation |
| 71 | Stack | Simplify path | python | explanation |
| 75 | Sorting | Sort colours | python | explanation |
| 78 | Recursion/Backtracking | Subsets | python | explanation |
| 79 | Recursion/Backtracking | Word search | python | explanation |
| 88 | Merge Sort | Merge Sorted Array | python | explanation |
| 92 | Linked List | Reverse linked list II | python | explanation |
| 102 | BFS | Binary tree level order traversal | python | explanation |
| 120 | DP | Triangle | python | explanation |
| 128 | Dictionary | Longest consecutive sequence | python | explanation |
| 129 | Backtracking/DFS | Sum root to leaf numbers | python | explanation |
| 138 | Linked List | Copy list with random pointer | python | explanation |
| 139 | DP/Memoize | Word break | python | explanation |
| 141 | Linked List | Linked list cycle | python | explanation |
| 153 | Binary Search | Find minimum in rotated sorted array | python | explanation |
| 162 | Binary Search | Find peak element | python | explanation |
| 167 | Two Pointers | Two sum II | python | explanation |
| 198 | DP | House robber | python | explanation |
| 199 | BFS | Binary tree right side view | python | explanation |
| 206 | Linked List | Reverse linked list | python | explanation |
| 211 | Trie, Recursion | Design add and search words data structure | python | explanation |
| 213 | DP | House robber II | python | explanation |
| 215 | Sorting, Recursion | Kth largest element in an array | python | explanation |
| 216 | Backtracking | Combination sum III | python | explanation |
| 219 | Sliding Window | Contains duplicate II | python | explanation |
| 227 | Stack, Queue | Basic calculator II | python | explanation |
| 231 | Bit Manipulation | Power of two | python | explanation |
| 236 | Binary Tree, BFS/DFS | Lowest common ancestor of a binary tree | python | explanation |
| 249 | Dictionary | Group shifted strings | python | explanation |
| 270 | Recursion | Closest Binary Search Tree Value | python | explanation |
| 296 | Array | Best meeting point | python | explanation |
| 301 | Backtracking, DFS | Remove invalid parantheses | python | explanation |
| 311 | Array | Sparse matrix multiplication | python | explanation |
| 314 | BFS/DFS | Binary tree vertical order traversal | python | explanation |
| 322 | DP/Memoize | Coin Change | python | explanation |
| 323 | DFS/Union Find | Number of connected components in an undirected graph | python | explanation |
| 339 | Recursion | Nested list weight sum | python | explanation |
| 346 | Queue | Moving average from data stream | python | explanation |
| 347 | Recursion, Quick select/Heap | Top k frequent elements | TODO | explanation |
| 351 | Backtracking | Android unlock patterns | python | explanation |
| 352 | BST, Dictionary | Data stream as disjoint intervals | python | explanation |
| 356 | Dictionary | Line Reflection | python | explanation |
| 362 | Queue | Design hit counter | python | explanation |
| 380 | List, Dictionary | Insert delete get random O(1) | python | explanation |
| 399 | BFS | Evaluate division | python | explanation |
| 406 | Sorting | Queue reconstruction by height | python | explanation |
| 408 | String | Valid word abbreviation | python | explanation |
| 415 | Array, String | Add strings | python | explanation |
| 426 | Recursion/Tree traversal | Convert binary search tree to sorted doubly linked list | python | explanation |
| 443 | Two Pointer/Queue | String compression | python | explanation |
| 452 | Sorting, Greedy | Minimum number of arrows to burst balloons | python | explanation |
| 465 | Array | Optimal Account Balancing | python | explanation |
| 516 | DP/Memoize | Longest palindromic subsequence | python | explanation |
| 518 | DP/Memoize | Coin change 2 | python | explanation |
| 523 | Dictionary, Array, Precompute prefix | Continuous subarray sum | python | explanation |
| 528 | Binary Search | Random pick with weight | python | explanation |
| 632 | Heap, Sliding Window | Smallest range covering rlements from K lists | python | explanation |
| 636 | Stack | Exclusive time of functions | python | explanation |
| 642 | Trie | Design search autocomplete system | python | explanation |
| 670 | Sorting, Array | Maximum swap | python | explanation |
| 680 | Recursion | Valid Palindrome II | python | explanation |
| 691 | Recursion/Backtracking | Stickers to spell word | python | explanation |
| 708 | Linked List | Insert into a sorted circular linked list | python | explanation |
| 719 | Binary Search, Sliding Window | Find k-th smallest pair distance | python | explanation |
| 721 | Connected Components | Accounts Merge | python | explanation |
| 751 | Binary strings | IP to CIDE | python | explanation |
| 766 | Array | Toeplitz matrix | python | explanation |
| 791 | Dictionary | Custom sort string | python | explanation |
| 799 | DP | Champagne Tower | python | explanation |
| 809 | Two Pointers | Expressive words | TODO | explanation |
| 827 | Connected Components, DFS | Expressive words | python | explanation |
| 856 | Stack | Score of parantheses | python | explanation |
| 871 | Greedy, Heap/DP | Minimum number of refuelling stops | python | explanation |
| 921 | Stack | Minimum add to make parantheses valid | python | explanation |
| 938 | Recursion | Range sum of BST | python | explanation |
| 973 | Heap | K closest points to origin | python | explanation |
| 978 | Sliding Window | Longest turbulent subarray | python | TODO |
| 980 | Backtracking | Unique paths III | python | explanation |
| 981 | Binary Search, Dictionary | Time based key value store | python | explanation |
| 1047 | Stack | Remove all adjacent duplicates | python | explanation |
| 1091 | BFS | Shortest path in binary matrix | TODO | explanation |
| 1162 | BFS | As far from land as possible | python | TODO |
| 1249 | Stack | Minimum remove to make valid parentheses | python | explanation |
| 1293 | BFS | Shortest path in a grid with obstacles elimination | python | explanation |
| 1306 | BFS/DFS | Jump Game III | python | explanation |
| 1331 | Sorting, Array/Dictionary | Rank transform of an array | python | explanation |
| 1512 | Dictionary | Number of good pairs | python | Explanation |
| 1535 | Array | Find the winner of an array game | python | Explanation |
| 1650 | Binary Tree | Lowest common ancestor of a binary tree III | python | Explanation |
| 1762 | Array | Buildings with an ocean view | python | explanation |
| 1926 | BFS | Nearest exit from entrance in maze | python | explanation |
| 2002 | Enumerative/DP | Max product of length of two palindromic subsequences | python | explanation |
| 2095 | Linked List | Delete the middle node of a linked list | python | explanation |
| 2115 | Recursion/Topological Sort | Find all possible recipes from given supplies | python | explanation |
| 2232 | String | Minimize result by adding parantheses to expression | python | explanation |
| 2251 | Queue, Heap | Number of flowers in full bloom | python | explanation |
| 2265 | Recursion/Tree Traversal | Count nodes equal to average of subtree | python | explanation |
| 2302 | Sliding Window | Count subarrays with score less than k | python | explanation |
| 2433 | Bit Manipulation | Find the original array of prefix XOR | python | explanation |
| 2483 | Array | Minimum penalty for a shop | python | explanation |
| 2815 | Array | Max pair sum in array | python | explanation |
| 2817 | Minimum absolute difference between elements with constraint | TODO | explanation | |
| 2843 | Array | Count symmetric integers | python | explanation |
| 2845 | Misc | Count of interesting sub arrays | python | explanation |
| 2859 | Bit Manipulation | Sum of values at indices with K set bits | python | explanation |
| 2860 | Queue, Stack, Sorting | Happy students | python | explanation |
| 2861 | Linear Programming/Binary Search | Maximum number of alloys | python | explanation |
| 3002 | Math, Sets | Maximum size of a set after removals | python | explanation |