Problem Difficulty Tags 1. Two Sum Easy *2. Add Two Numbers Medium 🔗 Linked List 9. Palindrome Number Easy 13. Roman to Integer Easy 14. Longest Common Prefix Easy String 20. Valid Parentheses Easy 21. Merge Two Sorted Lists Easy *35. Search Insert Position Easy 🌳 Binary Tree 53. Maximum Subarray Medium *57. Insert Interval Medium Array 66. Plus One Easy Array 67. Add Binary Easy 🌳 Binary Tree 70. Climbing Stairs Easy *98. Validate Binary Search Tree Medium 🌳 Binary Tree 100. Same Tree Easy 🌳 Binary Tree 101. Symmetric Tree Easy 🌳 Binary Tree *102. Binary Tree Level Order Traversal Medium 🌳 Binary Tree 104. Maximum Depth of Binary Tree Easy 🌳 Binary Tree *108. Convert Sorted Array to Binary Search Tree Easy 🌳 Binary Tree 110. Balanced Binary Tree Easy 🌳 Binary Tree 121. Best Time to Buy and Sell Stock Easy 136. Single Number Easy 💻 Bits 141. Linked List Cycle Easy 🔗 Linked List 155. Min Stack Medium Stack *190. Reverse Bits Easy 💻 Bits 191. Number of 1 Bits Easy 💻 Bits *199. Binary Tree Right Side View Medium 🌳 Binary Tree 169. Majority Element Easy 206. Reverse Linked List Easy 🔗 Linked List 217. Contains Duplicate Easy 232. Implement Queue using Stacks Easy 234. Palindrome Linked List Easy 🔗 Linked List 235. Lowest Common Ancestor of a Binary Search Tree Medium 🌳 Binary Tree *237. Delete Node in a Linked List Medium 🔗 Linked List 268. Missing Number Easy Array 278. First Bad Version Easy 283. Move Zeroes Easy *287. Find the Duplicate Number Medium 338. Counting Bits Easy 383. Ransom Note Easy 409. Longest Palindrome Easy 412. Fizz Buzz Easy *542. 01 Matrix Medium Dynamic Programming 543. Diameter of Binary Tree Easy 🌳 Binary Tree *572. Subtree of Another Tree Easy 🌳 Binary Tree 704. Binary Search Easy 🌳 Binary Tree 733. Flood Fill Easy 844. Backspace String Compare Easy 876. Middle of the Linked List Easy Array 976. Largest Perimeter Triangle Easy Array 977. Squares of a Sorted Array Easy 🔗 Linked List 1337. The K Weakest Rows in a Matrix Easy 1342. Number of Steps to Reduce a Number to Zero Easy 💻 Bits 1672. Richest Customer Wealth Easy Matrix 1920. Build Array from Permutation Easy Array 1929. Concatenation of Array Easy Array 2095. Delete the Middle Node of a Linked List Medium 🔗 Linked List 2235. Add Two Integers Easy Math Legend: * Needs review (didn’t come up with solution or implementation myself). This list is a work in progress.