Top 100 Liked Questions # Problems Difficulty Solution 001 Two_Sum Easy Java 002 Add Two Numbers Medium Java 003 Longest Substring Without Repeating Characters Medium Java 004 Median of Two Sorted Arrays Hard Java 005 Longest Palindromic Substring Medium Java 010 Regular Expression Matching Hard Java 011 Container With Most Water Medium Java 015 3Sum Medium Java 017 Letter Combinations of a Phone Number Medium Java 019 Remove Nth Node From End of List Easy Java 020 Valid Parentheses Easy Java 021 Merge Two Sorted Lists Easy Java 022 Generate Parentheses Medium Java 023 Merge k Sorted Lists Hard Java 032 Longest Valid Parentheses Hard Java 033 Search in Rotated Sorted Array Medium Java 034 Search for a Range Medium Java 035 Search Insert Position Medium Java 039 Combination Sum Medium Java 042 Trapping Rain Water Hard Java 046 Permutations Medium Java 048 Rotate Image Medium Java 049 Group Anagrams Medium Java 053 Maximum Subarray Medium Java 055 Jump Game Medium Java 056 Merge Intervals Medium Java 062 Unique Paths Medium Java 064 Minimum Path Sum Medium Java 070 Climbing Stairs Easy Java 072 Edit Distance Hard Java 075 Sort Colors Medium Java 076 Minimum Window Substring Hard Java 078 Subsets Medium Java 079 Word Search Medium Java 084 Largest Rectangle in Histogram Hard Java 085 Maximal Rectangle Hard Java 094 Binary Tree Inorder Traversal Medium Java 096 Unique Binary Search Trees Medium Java 098 Validate Binary Search Tree Medium Java 101 Symmetric Tree Easy Java 102 Binary Tree Level Order Traversal Easy Java 104 Maximum Depth of Binary Tree Easy Java 105 Construct Binary Tree from Preorder and Inorder Traversal Medium Java 114 Flatten Binary Tree to Linked List Medium Java 121 Best Time to Buy and Sell Stock Easy Java 124 Binary Tree Maximum Path Sum Hard Java 128 Longest Consecutive Sequence Hard Java 136 Single Number Easy Java 139 Word Break Medium Java 141 Linked List Cycle Easy Java 142 Linked List Cycle II Medium Java 146 LRU Cache Hard Java 148 Sort List Medium Java 152 Maximum Product Subarray Medium Java 155 Min Stack Easy Java 160 Intersection of Two Linked Lists Easy Java 169 Majority Element Easy Java 198 House Robber Easy Java 200 Number of Islands Medium Java 206 Reverse Linked List Easy Java 207 Course Schedule Medium Java 208 Implement Trie (Prefix Tree) Medium Java 215 Kth Largest Element in an Array Medium Java 221 Maximal Square Medium Java 226 Invert Binary Tree Easy Java 234 Palindrome Linked List Easy Java 236 Lowest Common Ancestor of a Binary Tree Medium Java 238 Product of Array Except Self Medium Java 239 Sliding Window Maximum Hard Java 240 Search a 2D Matrix II Medium Java 253 Meeting Rooms II Medium 没权限 279 Perfect Squares Medium Java 283 Move Zeroes Easy Java 287 Find the Duplicate Number Hard Java 297 Serialize and Deserialize Binary Tree Hard Java 300 Longest Increasing Subsequence Medium Java 301 Remove Invalid Parentheses Hard Java 309 Best Time to Buy and Sell Stock with Cooldown Medium Java 312 Burst Balloons Hard Java 322 Coin Change Medium Java 337 House Robber III Medium Java 338 Counting Bits Medium Java 347 Top K Frequent Elements Medium Java 394 Decode String Medium Java 406 Queue Reconstruction by Height Medium Java 416 Partition Equal Subset Sum Medium Java 437 Path Sum III Easy Java 438 Find All Anagrams in a String Easy Java 448 Find All Numbers Disappeared in an Array Easy Java 461 Hamming Distance Easy Java 494 Target Sum Medium Java 538 Convert BST to Greater Tree Easy Java 543 Diameter of Binary Tree Easy Java 560 Subarray Sum Equals K Medium Java 572 Subtree of Another Tree Easy Java 581 Shortest Unsorted Continuous Subarray Easy Java 617 Merge Two Binary Trees Easy Java 621 Task Scheduler Medium Java 647 Palindromic Substrings Medium Java 771 Jewels and Stones Easy Java