ID Problem Solution Difficulty Remark 0001 Two Sum Solution Easy 0002 Add Two Numbers Solution Medium 0003 Longest Substring Without Repeating Characters Solution Medium 0004 Median of Two Sorted Arrays Solution Hard 0005 Longest Palindromic Substring Solution Medium To Optimize 0006 ZigZag Conversion Solution Medium 0007 Reverse Integer Solution Easy 0008 String to Integer (atoi) Solution Medium Not Recommend 0009 Palindrome Number Solution Easy 0011 Container With Most Water Solution Medium 0013 Roman to Integer Solution Easy Not Recommend 0014 Longest Common Prefix Solution Easy 0015 3Sum Solution Medium 0016 3Sum Closest Solution Medium 0017 Letter Combinations of a Phone Number Solution Medium 0018 4Sum Solution Medium 0019 Remove Nth Node From End of List Solution Medium Double-Pointer 0020 Valid Parentheses Solution Easy 0021 Merge Two Sorted Lists Solution Easy 0026 Remove Duplicates from Sorted Array Solution Easy 0027 Remove Element Solution Easy 0035 Search Insert Position Solution Easy 0039 Combination Sum Solution Medium Backtracing 0040 Combination Sum II Solution Medium Backtracing 0046 Permutations Solution Medium 0047 Permutations Solution Medium Backtracing 0049 Group Anagrams Solution Medium 0051 N-Queens Solution Hard BackTracing 0052 N-Queens II Solution Hard BackTracing 0053 Maximum Subarray Solution Easy DP 0062 Unique Paths Solution Medium 0063 Unique Paths II Solution Medium 0064 Minimum Path Sum Solution Medium 0066 Plus One Solution Easy 0070 Climbing Stairs Solution Easy 0075 Sort Colors Solution Medium 0076 Minimum Window Substring Solution Hard 0080 Remove Duplicates from Sorted Array II Solution Medium 0088 Merge Sorted Array Solution Easy 0091 Decode Ways Solution Medium 0093 Restore IP Addresses Solution Medium 0096 Unique Binary Search Trees Solution Medium 0104 Maximum Depth of Binary Tree Solution Easy Recursion 0120 Triangle Solution Medium 0121 Best Time to Buy and Sell Stock Solution Easy DP 0122 Best Time to Buy and Sell Stock II Solution Easy DP 0123 Best Time to Buy and Sell Stock III Solution Hard DP 0125 Valid Palindrome Solution Medium 0131 Palindrome Partitioning Solution Medium 0149 Max Points on a Line Solution Hard 0167 Two Sum II - Input array is sorted Solution Easy 0188 Best Time to Buy and Sell Stock IV Solution Hard DP 0198 House Robber Solution Easy 0199 Binary Tree Right Side View Solution Medium BackTracing 0202 Happy Number Solution Easy 0203 Remove Linked List Elements Solution Easy 0205 Isomorphic Strings Solution Easy 0206 Reverse Linked List Solution Easy 0208 Implement Trie (Prefix Tree) Solution Medium 0209 Minimum Size Subarray Sum Solution Medium 0211 Add and Search Word - Data structure design Solution Medium 0213 House Robber II Solution Medium 0215 Kth Largest Element in an Array Solution Medium 0216 Combination Sum III Solution Medium Backtracing 0217 Contains Duplicate Solution Easy 0219 Contains Duplicate II Solution Easy 0220 Contains Duplicate III Solution Medium 0242 Valid Anagram Solution Easy 0279 Valid Anagram Solution Medium 0283 Move Zeroes Solution Easy 0290 Word Pattern Solution Easy 0300 Longest Increasing Subsequence Solution Medium 0303 Range Sum Query - Immutable Solution Easy 0307 Range Sum Query - Mutable Solution Medium 0309 Best Time to Buy and Sell Stock with Cooldown Solution Medium DP 0332 Reconstruct Itinerary Solution Medium Graph 0338 Counting Bits Solution Medium 0343 Integer Break Solution Medium 0344 Reverse String Solution Easy 0345 Reverse Vowels of a String Solution Easy 0347 Top K Frequent Elements Solution Medium 0349 Intersection of Two Arrays Solution Easy 0350 Intersection of Two Arrays II Solution Easy 0376 Wiggle Subsequence Solution Medium 0438 Find All Anagrams in a String Solution Medium 0447 Number of Boomerangs Solution Easy 0454 4Sum II Solution Medium 0530 Minimum Absolute Difference in BST Solution Easy 0557 Reverse Words in a String III Solution Easy 0606 Construct String from Binary Tree Solution Easy 0677 Map Sum Pairs Solution Medium 0700 Search in a Binary Search Tree Solution Easy 0783 Minimum Distance Between BST Nodes Solution Easy 0804 Unique Morse Code Words Solution Easy 0877 Stone Game Solution Medium 0938 Range Sum of BST Solution Easy 1025 Divisor Game Solution Easy
