1 Two Sum 2 Add Two Numbers 146 LRU Cache 5 Longest Palindromic Substring 4 Median of Two Sorted Arrays 42 Trapping Rain Water 3 Longest Substring Without Repeating Characters 200 Number of Islands 15 3Sum 53 Maximum Subarray 21 Merge Two Sorted Lists 20 Valid Parentheses 23 Merge k Sorted Lists 937 Reorder Data in Log Files 206 Reverse Linked List 238 Product of Array Except Self 273 Integer to English Words 56 Merge Intervals 297 Serialize and Deserialize Binary Tree 76 Minimum Window Substring 289 Game of Life 301 Remove Invalid Parentheses 973 K Closest Points to Origin 253 Meeting Rooms II 11 Container With Most Water 202 Happy Number 121 Best Time to Buy and Sell Stock 54 Spiral Matrix 49 Group Anagrams 22 Generate Parentheses 68 Text Justification 33 Search in Rotated Sorted Array 7 Reverse Integer 88 Merge Sorted Array 380 Insert Delete GetRandom O(1) 560 Subarray Sum Equals K 17 Letter Combinations of a Phone Number 336 Palindrome Pairs 91 Decode Ways 394 Decode String 41 First Missing Positive 79 Word Search 46 Permutations 609 Find Duplicate File in System 31 Next Permutation 85 Maximal Rectangle 138 Copy List with Random Pointer 10 Regular Expression Matching 13 Roman to Integer 175 Combine Two Tables 269 Alien Dictionary 1007 Minimum Domino Rotations For Equal Row 741 Cherry Pickup 312 Burst Balloons 139 Word Break 127 Word Ladder 218 The Skyline Problem 295 Find Median from Data Stream 344 Reverse String 155 Min Stack 393 UTF-8 Validation 410 Split Array Largest Sum 322 Coin Change 6 ZigZag Conversion 221 Maximal Square 412 Fizz Buzz 539 Minimum Time Difference 9 Palindrome Number 12 Integer to Roman 212 Word Search II 124 Binary Tree Maximum Path Sum 51 N-Queens 981 Time Based Key-Value Store 642 Design Search Autocomplete System 362 Design Hit Counter 535 Encode and Decode TinyURL 547 Friend Circles 32 Longest Valid Parentheses 1048 Longest String Chain 125 Valid Palindrome 72 Edit Distance 332 Reconstruct Itinerary 166 Fraction to Recurring Decimal 176 Second Highest Salary 986 Interval List Intersections 341 Flatten Nested List Iterator 70 Climbing Stairs 215 Kth Largest Element in an Array 45 Jump Game II 25 Reverse Nodes in k-Group 364 Nested List Weight Sum II 771 Jewels and Stones 460 LFU Cache 315 Count of Smaller Numbers After Self 24 Swap Nodes in Pairs 39 Combination Sum 811 Subdomain Visit Count 37 Sudoku Solver 529 Minesweeper 347 Top K Frequent Elements