LeetCode Solutions LeetCode # Title Solution Difficulty 1 Two Sum JAVA Easy 2 Add Two Numbers JAVA Medium 3 Longest Substring Without Repeating Characters JAVA Medium 5 Longest Palindromic Substring JAVA Medium 6 ZigZag Conversion JAVA Medium 7 Reverse Integer JAVA Easy 9 Palindrome Number JAVA Easy 10 Regular Expression Matching JAVA Hard 11 Container With Most Water JAVA Medium 12 Integer to Roman JAVA Medium 15 3Sum JAVA Medium 17 Letter Combinations of a Phone Number JAVA Medium 19 Remove Nth Node From End of List JAVA Medium 20 Valid Parentheses JAVA Easy 21 Merge Two Sorted Lists JAVA Easy 22 Generate Parentheses JAVA Medium 29 Divide Two Integers JAVA Medium 31 Next Permutation JAVA Medium 33 Search in Rotated Sorted Array JAVA Medium 34 Find First and Last Position of Element in Sorted Array JAVA Medium 35 Search Insert Position JAVA Easy 36 Valid Sudoku JAVA Medium 39 Combination Sum JAVA Medium 46 Permutations JAVA Medium 48 Rotate Image JAVA Medium 49 Group Anagrams JAVA Medium 50 Pow(x, n) JAVA Medium 53 Maximum Subarray JAVA Easy 54 Spiral Matrix JAVA Medium 55 Jump Game JAVA Medium 56 Merge Intervals JAVA Medium 59 Spiral Matrix II JAVA Medium 60 Permutation Sequence JAVA Medium 62 Unique Paths JAVA Medium 63 Unique Paths II JAVA Medium 64 Minimum Path Sum JAVA Medium 66 Plus One JAVA Easy 67 Add Binary JAVA Easy 70 Climbing Stairs JAVA Easy 73 Set Matrix Zeroes JAVA Medium 74 Search a 2D Matrix JAVA Medium 75 Sort Colors JAVA Medium 78 Subsets JAVA Medium 79 Word Search JAVA Medium 80 Remove Duplicates from Sorted Array II JAVA Medium 81 Search in Rotated Sorted Array II JAVA Medium 83 Remove Duplicates from Sorted List JAVA Easy 91 Decode Ways JAVA Medium 94 Binary Tree Inorder Traversal JAVA Medium 96 Unique Binary Search Trees JAVA Medium 98 Validate Binary Search Tree JAVA Medium 101 Symmetric Tree JAVA Easy 102 Binary Tree Level Order Traversal JAVA Medium 103 Binary Tree Zigzag Level Order Traversal JAVA Medium 104 Maximum Depth of Binary Tree JAVA Easy 105 Construct Binary Tree from Preorder and Inorder Traversal JAVA Medium 108 Convert Sorted Array to Binary Search Tree JAVA Medium 114 Flatten Binary Tree to Linked List JAVA Medium 116 Populating Next Right Pointers in Each Node JAVA Medium 118 Pascal's Triangle JAVA Easy 121 Best Time to Buy and Sell Stock JAVA Easy 122 Best Time to Buy and Sell Stock II JAVA Easy 123 Valid Palindrome JAVA Easy 124 Binary Tree Maximum Path Sum JAVA Hard 136 Single Number JAVA Easy 139 Word Break JAVA Medium 141 Linked List Cycle JAVA Easy 142 Linked List Cycle II JAVA Medium 146 LRU Cache JAVA Medium 148 Sort List JAVA Medium