203 efficient solutions to LeetCode problems # Question Solution Difficulty 1 Two Sum Solution Easy 2 Add Two Numbers Solution Medium 4 Median of Two Sorted Arrays Solution Hard 5 Longest Palindromic Substring Solution Medium 7 Reverse Integer Solution Easy 9 Palindrome Number Solution Easy 13 Roman to Integer Solution Easy 14 Longest Common Prefix Solution Easy 15 3sum Solution Medium 16 3sum Closest Solution Medium 17 Letter Combinations of a Phone Number Solution Medium 19 Remove Nth Node From End of List Solution Medium 20 Valid Parentheses Solution Easy 21 Merge Two Sorted Lists Solution Easy 22 Generate Parentheses Solution Medium 23 Merge k Sorted Lists Solution Hard 26 Remove Duplicates from Sorted Array Solution Easy 27 Remove Element Solution Easy 28 Implement strStr() Solution Easy 33 Search in Rotated Sorted Array Solution Medium 34 Find First and Last Position of Element in Sorted Array Solution Medium 35 Search Insert Position Solution Easy 38 Count and Say Solution Easy 42 Trapping Rain Water Solution Hard 46 Permutations Solution Medium 47 Permutations II Solution Medium 48 Rotate Image Solution Medium 49 Group Anagrams Solution Medium 51 N-Queens Solution Hard 52 N-Queens II Solution Hard 53 Maximum Subarray Solution Easy 55 Jump Game Solution Medium 58 Length of Last Word Solution Easy 62 Unique Paths Solution Medium 63 Unique Paths II Solution Medium 66 Plus One Solution Easy 67 Add Binary Solution Easy 69 Sqrt(x) Solution Easy 70 Climbing Stairs Solution Easy 73 Set Matrix Zeroes Solution Medium 78 Subsets Solution Medium 80 Remove Duplicates from Sorted Array II Solution Medium 81 Search in Rotated Sorted Array II Solution Medium 82 Remove Duplicates from Sorted List II Solution Medium 83 Remove Duplicates from Sorted List Solution Easy 88 Merge Sorted Array Solution Easy 90 Subsets II Solution Medium 92 Reverse Linked List II Solution Medium 94 Binary Tree Inorder Traversal Solution Medium 98 Validate Binary Search Tree Solution Medium 100 Same Tree Solution Easy 101 Symmetric Tree Solution Easy 102 Binary Tree Level Order Traversal Solution Medium 104 Maximum Depth of Binary Tree Solution Easy 107 Binary Tree Level Order Traversal II Solution Easy 108 Convert Sorted Array to Binary Search Tree Solution Easy 110 Balanced Binary Tree Solution Easy 111 Minimum Depth of Binary Tree Solution Easy 118 Pascal's Triangle Solution Easy 119 Pascal's Triangle II Solution Easy 121 Best Time to Buy and Sell Stock Solution Easy 122 Best Time to Buy and Sell Stock II Solution Easy 125 Valid Palindrome Solution Easy 127 Word Ladder Solution Medium 136 Single Number Solution Easy 139 Word Break Solution Medium 141 Linked List Cycle Solution Easy 142 Linked List Cycle II Solution Medium 143 Reorder List Solution Medium 144 Binary Tree Preorder Traversal Solution Medium 145 Binary Tree Postorder Traversal Solution Hard 146 LRU Cache Solution Medium 148 Sort List Solution Medium 149 Max Points on a Line Solution Hard 151 Reverse Words in a String Solution Medium 155 Min Stack Solution Easy 160 Intersection of Two linked Lists Solution Easy 162 Find Peak Element Solution Medium 167 Two Sum II - Input array is sorted Solution Easy 168 Excel Sheet Column Title Solution Easy 169 Majority Element Solution Easy 171 Excel Sheet Column Number Solution Easy 172 Factorial Trailing Zeroes Solution Easy 175 Combine Two Tables Solution Easy 176 Second Highest Salary Solution Easy 177 Nth Highest Salary Solution Medium 178 Rank Scores Solution Medium 180 Consecutive Numbers Solution Medium 181 Employees Earning More Than Their Managers Solution Easy 182 Duplicate Emails Solution Easy 183 Customers Who Never Order Solution Easy 184 Department Highest Salary Solution Medium 185 Department Top Three Salaries Solution Hard 189 Rotate Array Solution Easy 190 Reverse Bits Solution Easy 191 Number of 1 Bits Solution Easy 196 Delete Duplicate Emails Solution Easy 197 Rising Temperature Solution Easy 198 House Robber Solution Easy 200 Number of Islands Solution Medium 202 Happy Number Solution Easy 203 Remove Linked List Elements Solution Easy 204 Count Primes Solution Easy 206 Reverse Linked List Solution Easy 207 Course Schedule Solution Medium 208 Implement Trie (Prefix Tree) Solution Medium 210 Course Schedule II Solution Medium 217 Contains Duplicate Solution Easy 226 Invert Binary Tree Solution Easy 231 Power of Two Solution Easy 232 Implement Queue using Stacks Solution Easy 234 Palindrome Linked List Solution Easy 235 Lowest Common Ancestor of a Binary Search Tree Solution Easy 236 Lowest Common Ancestor of a Binary Tree Solution Medium 237 Delete Node in a Linked List Solution Easy 238 Product of Array Except Self Solution Medium 239 Sliding Window Maximum Solution Hard 240 Search a 2D Matrix II Solution Medium 242 Valid Anagram Solution Easy 262 Trips and Users Solution Hard 263 Ugly Number Solution Easy 264 Ugly Number II Solution Medium 268 Missing Number Solution Easy 273 Integer to English Words Solution Hard 278 First Bad Version Solution Easy 283 Move Zeroes Solution Easy 290 Word Pattern Solution Easy 292 Nim Game Solution Easy 295 Find Median from Data Stream Solution Hard 300 Longest Increasing Subsequence Solution Medium 303 Range Sum Query - Immutable Solution Easy 309 Best Time to Buy and Sell Stock with Cooldown Solution Medium 326 Power of Three Solution Easy 328 Odd Even Linked List Solution Medium 342 Power of Four Solution Easy 344 Reverse String Solution Easy 347 Top K Frequent Elements Solution Medium 349 Intersection of Two Arrays Solution Easy 350 Intersection of Two Arrays II Solution Easy 354 Russian Doll Envelopes Solution Hard 367 Valid Perfect Square Solution Easy 371 Sum of Two Integers Solution Easy 380 Insert Delete GetRandom O(1) Solution Medium 381 Insert Delete GetRandom O(1) - Duplicates allowed Solution Hard 383 Ransom Note Solution Easy 384 Shuffle an Array Solution Medium 387 First Unique Character in a String Solution Easy 389 Find the Difference Solution Easy 412 Fizz Buzz Solution Easy 414 Third Maximum Number Solution Easy 429 N-ary Tree Level Order Traversal Solution Easy 437 Path Sum III Solution Easy 442 Find All Duplicates in an Array Solution Medium 443 String Compression Solution Easy 445 Add Two Numbers II Solution Medium 448 Find All Numbers Disappeared in an Array Solution Easy 454 4Sum II Solution Medium 461 Hamming Distance Solution Easy 470 Implement Rand10() Using Rand7() Solution Medium 477 Total Hamming Distance Solution Medium 480 Sliding Window Median Solution Hard 500 Keyboard Row Solution Easy 509 Fibonacci Number Solution Easy 516 Longest Palindromic Subsequence Solution Medium 518 Coin Change 2 Solution Medium 520 Detect Capital Solution Easy 525 Contiguous Array Solution Medium 543 Diameter of Binary Tree Solution Easy 559 Maximum Depth of N-ary Tree Solution Easy 560 Subarray Sum Equals K Solution Medium 572 Subtree of Another Tree Solution Easy 581 Shortest Unsorted Continuous Subarray Solution Easy 589 N-ary Tree Preorder Traversal Solution Easy 590 N-ary Tree Postorder Traversal Solution Easy 595 Big Countries Solution Easy 596 Classes More Than 5 Students Solution Easy 601 Human Traffic of Stadium Solution Hard 617 Merge Two Binary Trees Solution Easy 620 Not Boring Movies Solution Easy 626 Exchange Seats Solution Medium 627 Swap Salary Solution Easy 692 Top K Frequent Words Solution Medium 695 Max Area of Island Solution Medium 703 Kth Largest Element in a Stream Solution Easy 704 Binary Search Solution Easy 706 Design HashMap Solution Easy 707 Design Linked List Solution Easy 709 To Lower Case Solution Easy 733 Flood Fill Solution Easy 771 Jewels and Stones Solution Easy 895 Maximum Frequency Stack Solution Hard 912 Sort an Array Solution Medium 976 Largest Perimeter Triangle Solution Easy 1010 Pairs of Songs With Total Durations Divisible by 60 Solution Easy 1092 Shortest Common Supersequence Solution Hard 1114 Print in Order Solution Easy 1115 Print FooBar Alternately Solution Medium 1116 Print Zero Even Odd Solution Medium 1117 Building H2O Solution Medium 1139 Largest 1-Bordered Square Solution Medium 1179 Reformat Department Table Solution Easy 1195 Fizz Buzz Multithreaded Solution Medium 1207 Unique Number of Occurrences Solution Easy
