111 efficient solutions to LeetCode problems # Question Solution Difficulty 1 Two Sum Solution Easy 2 Add Two Numbers Solution Medium 4 Median of Two Sorted Arrays Solution Hard 5 Longest Palindromic Substring Solution Medium 15 3sum Solution Medium 16 3sum Closest Solution Medium 17 Letter Combinations of a Phone Number Solution Medium 19 Remove Nth Node From End of List Solution Medium 20 Valid Parentheses Solution Easy 21 Merge Two Sorted Lists Solution Easy 22 Generate Parentheses Solution Medium 23 Merge k Sorted Lists Solution Hard 28 Implement strStr() Solution Easy 33 Search in Rotated Sorted Array Solution Medium 42 Trapping Rain Water Solution Hard 46 Permutations Solution Medium 47 Permutations II Solution Medium 48 Rotate Image Solution Medium 49 Group Anagrams Solution Medium 51 N-Queens Solution Hard 52 N-Queens II Solution Hard 53 Maximum Subarray Solution Easy 55 Jump Game Solution Medium 62 Unique Paths Solution Medium 63 Unique Paths II Solution Medium 70 Climbing Stairs Solution Easy 73 Set Matrix Zeroes Solution Medium 78 Subsets Solution Medium 81 Search in Rotated Sorted Array II Solution Medium 90 Subsets II Solution Medium 92 Reverse Linked List II Solution Medium 94 Binary Tree Inorder Traversal Solution Medium 98 Validate Binary Search Tree Solution Medium 102 Binary Tree Level Order Traversal Solution Medium 104 Maximum Depth of Binary Tree Solution Easy 108 Convert Sorted Array to Binary Search Tree Solution Easy 110 Balanced Binary Tree Solution Easy 127 Word Ladder Solution Medium 136 Single Number Solution Easy 139 Word Break Solution Medium 141 Linked List Cycle Solution Easy 142 Linked List Cycle II Solution Medium 143 Reorder List Solution Medium 144 Binary Tree Preorder Traversal Solution Medium 145 Binary Tree Postorder Traversal Solution Hard 146 LRU Cache Solution Medium 148 Sort List Solution Medium 149 Max Points on a Line Solution Hard 151 Reverse Words in a String Solution Medium 155 Min Stack Solution Easy 160 Intersection of Two linked Lists Solution Easy 162 Find Peak Element Solution Medium 169 Majority Element Solution Easy 172 Factorial Trailing Zeroes Solution Easy 189 Rotate Array Solution Easy 200 Number of Islands Solution Medium 206 Reverse Linked List Solution Easy 207 Course Schedule Solution Medium 208 Implement Trie (Prefix Tree) Solution Medium 210 Course Schedule II Solution Medium 231 Power of Two Solution Easy 232 Implement Queue using Stacks Solution Easy 234 Palindrome Linked List Solution Easy 235 Lowest Common Ancestor of a Binary Search Tree Solution Easy 236 Lowest Common Ancestor of a Binary Tree Solution Medium 237 Delete Node in a Linked List Solution Easy 239 Sliding Window Maximum Solution Hard 240 Search a 2D Matrix II Solution Medium 242 Valid Anagram Solution Easy 264 Ugly Number II Solution Medium 268 Missing Number Solution Easy 273 Integer to English Words Solution Hard 290 Word Pattern Solution Easy 295 Find Median from Data Stream Solution Hard 300 Longest Increasing Subsequence Solution Medium 347 Top K Frequent Elements Solution Medium 354 Russian Doll Envelopes Solution Hard 371 Sum of Two Integers Solution Easy 380 Insert Delete GetRandom O(1) Solution Medium 381 Insert Delete GetRandom O(1) - Duplicates allowed Solution Hard 383 Ransom Note Solution Easy 384 Shuffle an Array Solution Medium 429 N-ary Tree Level Order Traversal Solution Easy 437 Path Sum III Solution Easy 443 String Compression Solution Easy 445 Add Two Numbers II Solution Medium 454 4Sum II Solution Medium 470 Implement Rand10() Using Rand7() Solution Medium 509 Fibonacci Number Solution Easy 516 Longest Palindromic Subsequence Solution Medium 518 Coin Change 2 Solution Medium 525 Contiguous Array Solution Medium 559 Maximum Depth of N-ary Tree Solution Easy 560 Subarray Sum Equals K Solution Medium 572 Subtree of Another Tree Solution Easy 581 Shortest Unsorted Continuous Subarray Solution Easy 589 N-ary Tree Preorder Traversal Solution Easy 590 N-ary Tree Postorder Traversal Solution Easy 692 Top K Frequent Words Solution Medium 695 Max Area of Island Solution Medium 703 Kth Largest Element in a Stream Solution Easy 704 Binary Search Solution Easy 706 Design HashMap Solution Easy 707 Design Linked List Solution Easy 733 Flood Fill Solution Easy 912 Sort an Array Solution Medium 976 Largest Perimeter Triangle Solution Easy 1010 Pairs of Songs With Total Durations Divisible by 60 Solution Easy 1092 Shortest Common Supersequence Solution Hard 1114 Print in Order Solution Easy 1139 Largest 1-Bordered Square Solution Medium
