| 1 Two Sum |
Hash map |
| 3 Longest Substring Without Repeating Characters |
Sliding window, hash map |
| 5 Longest Palindromic Substring |
Expand-around-center, DP |
| 9 Palindrome Number |
Math, string handling |
| 10 Regular Expression Matching |
Dynamic Programming |
| 11 Container With Most Water |
Two-pointers |
| 15 3Sum |
hash, sorting |
| 16 3Sum Closest |
Sorting, two-pointers |
| 18 4Sum |
Hash, sorting, two-pointers |
| 20 Valid Parentheses |
Stack |
| 22 Generate Parentheses |
Backtracking |
| 26 Remove Duplicates from Sorted Array |
Two-pointers |
| 27 Remove Element |
Two-pointers |
| 28 Find the index of the First Occurrence in a String |
String matching, KMP |
| 31 Next Permutation |
Array, reverse suffix |
| 33 Search in Rotated Sorted Array |
Modified binary search |
| 37 Sudoku Solver |
Backtracking, constraint checking |
| 42 Trapping Rain Water |
Two-pointers, monotonic stack |
| 44 Wildcard Matching |
Dynamic Programming |
| 45 Jump Game II |
Greedy |
| 48 Rotate Image |
Matrix rotation, in-place |
| 49 Group Anagrams |
Sorting, hash map |
| 51 N-Queens |
Backtracking |
| 53 Maximum Subarray |
Kadane's algorithm, divide and conquer |
| 54 Spiral Matrix |
Simulation, boundaries |
| 66 Plus One |
Array manipulation, carry |
| 67 Add Binary |
String manipulation, carry |
| 75 Sort Colors |
Dutch National Flag, two-pointers |
| 92 Reverse Linked List II |
Linked list, in-place reversal |
| 121 Best Time to Buy and Sell Stock |
One-pass, greedy |
| 128 Longest Consecutive Sequence |
Hash set |
| 152 Maximum Product Subarray |
Dynamic Programming |
| 169 Majority Element |
Hash map, Boyer-Moore voting |
| 175 Combine Two Tables |
SQL JOIN |
| 189 Rotate Array |
Reverse, cycle replacement |
| 198 House Robber |
Dynamic Programming |
| 202 Happy Number |
Hash set, Floyd cycle detection |
| 206 Reverse Linked List |
Iterative, recursive |
| 231 Power of Two |
Bit manipulation |
| 239 Sliding Window Maximum |
Monotonic deque, sliding window |
| 283 Move Zeros |
Two-pointers, in-place |
| 349 Intersection of Two Arrays |
Hash set |
| 394 Decode String |
Stack, recursion |
| 410 Split Array Largest Sum |
Binary search, greedy |
| 560 Subarray Sum Equals K |
Prefix sum, hash map |
| 584 Find Customer Referee |
SQL filtering, NULL handling |
| 643 Maximum Average Subarray I |
Sliding window |
| 796 Rotate String |
String manipulation, rotation check |
| 875 Koko Eating Bananas |
Binary search |
| 912 Sort an Array |
Merge sort, quicksort |
| 1768 Merge Strings Alternately |
Two-pointers |
| 2667 Create Hello World Function |
Closure, higher-order function |