ID Title Difficulty Note Java Python 1 Two Sum Easy noNote Java Python 2 Add Two Numbers Medium noNote Java Python 3 Longest Substring Without Repeating Characters Medium noNote Java Python 4 Median of Two Sorted Arrays Hard noNote no no 5 Longest Palindromic Substring Medium noNote no no 6 ZigZag Conversion Medium noNote Java Python 7 Reverse Integer Easy noNote Java Python 8 String to Integer (atoi) Medium noNote Java no 9 Palindrome Number Easy noNote Java Python 10 Regular Expression Matching Hard noNote Java no 11 Container With Most Water Medium noNote Java no 12 Integer to Roman Medium noNote Java Python 13 Roman to Integer Easy noNote Java Python 14 Longest Common Prefix Easy noNote Java Python 15 3Sum Medium noNote Java Python 16 3Sum Closest Medium noNote Java no 17 Letter Combinations of a Phone Number Medium noNote Java Python 18 4Sum Medium noNote Java no 19 Remove Nth Node From End of List Medium noNote Java Python 20 Valid Parentheses Easy noNote Java no 21 Merge Two Sorted Lists Easy noNote Java Python 22 Generate Parentheses Medium noNote Java Python 23 Merge k Sorted Lists Hard noNote Java Python 24 Swap Nodes in Pairs Medium noNote Java Python 25 Reverse Nodes in k-Group Hard noNote Java no 26 Remove Duplicates from Sorted Array Easy noNote Java Python 27 Remove Element Easy noNote Java Python 28 Implement strStr() Easy noNote Java no 29 Divide Two Integers Medium noNote Java no 30 Substring with Concatenation of All Words Hard noNote no no 31 Next Permutation Medium noNote Java Python 32 Longest Valid Parentheses Hard noNote Java no 33 Search in Rotated Sorted Array Medium noNote Java no 34 Search for a Range Medium noNote Java Python 35 Search Insert Position Easy noNote Java Python 36 Valid Sudoku Medium noNote Java no 37 Sudoku Solver Hard noNote Java no 38 Count and Say Easy noNote Java no 39 Combination Sum Medium noNote Java Python 40 Combination Sum II Medium noNote Java no 41 First Missing Positive Hard noNote Java Python 42 Trapping Rain Water Hard noNote Java no 43 Multiply Strings Medium noNote Java Python 44 Wildcard Matching Hard noNote no no 45 Jump Game II Hard noNote Java no 46 Permutations Medium noNote Java Python 47 Permutations II Medium noNote Java Python 48 Rotate Image Medium noNote Java Python 49 Group Anagrams Medium noNote Java Python 50 Pow(x, n) Medium noNote Java Python 51 N-Queens Hard noNote Java Python 52 N-Queens II Hard noNote Java Python 53 Maximum Subarray Easy noNote Java Python 54 Spiral Matrix Medium noNote Java Python 55 Jump Game Medium noNote Java Python 56 Merge Intervals Medium noNote Java no 57 Insert Interval Hard noNote Java Python 58 Length of Last Word Easy noNote Java Python 59 Spiral Matrix II Medium noNote Java Python 60 Permutation Sequence Medium noNote Java Python 61 Rotate List Medium noNote Java Python 62 Unique Paths Medium noNote Java Python 63 Unique Paths II Medium noNote Java Python 64 Minimum Path Sum Medium noNote Java Python 65 Valid Number Hard noNote no no 66 Plus One Easy noNote Java no 67 Add Binary Easy noNote Java Python 68 Text Justification Hard noNote Java Python 69 Sqrt(x) Easy noNote Java Python 70 Climbing Stairs Easy noNote Java Python 71 Simplify Path Medium noNote no no 72 Edit Distance Hard noNote Java Python 73 Set Matrix Zeroes Medium noNote Java Python 74 Search a 2D Matrix Medium noNote Java Python 75 Sort Colors Medium noNote Java Python 76 Minimum Window Substring Hard noNote no no 77 Combinations Medium noNote Java Python 78 Subsets Medium noNote Java Python 79 Word Search Medium noNote Java no 80 Remove Duplicates from Sorted Array II Medium noNote Java Python 81 Search in Rotated Sorted Array II Medium noNote Java no 82 Remove Duplicates from Sorted List II Medium noNote Java Python 83 Remove Duplicates from Sorted List Easy noNote Java Python 84 Largest Rectangle in Histogram Hard noNote no no 85 Maximal Rectangle Hard noNote no no 86 Partition List Medium noNote Java Python 87 Scramble String Hard noNote Java Python 88 Merge Sorted Array Easy noNote Java Python 89 Gray Code Medium noNote Java Python 90 Subsets II Medium noNote Java Python 91 Decode Ways Medium noNote Java Python 92 Reverse Linked List II Medium noNote Java no 93 Restore IP Addresses Medium noNote Java Python 94 Binary Tree Inorder Traversal Medium noNote Java Python 95 Unique Binary Search Trees II Medium noNote Java no 96 Unique Binary Search Trees Medium noNote Java Python 97 Interleaving String Hard noNote Java Python 98 Validate Binary Search Tree Medium noNote Java Python 99 Recover Binary Search Tree Hard noNote no Python 100 Same Tree Easy noNote Java Python