A list of the best LeetCode questions that teach you core concepts and techniques for each category/type of problem. Many other LeetCode questions are a mashup of the techniques from these individual questions.
- Two Sum
- Best Time to Buy and Sell Stock
- Contains Duplicate
- Product of Array Except Self
- Maximum Subarray
- Maximum Product Subarray
- Find Minimum in Rotated Sorted Array
- Search in Rotated Sorted Array
- 3Sum
- Container With Most Water
- Climbing Stairs
- Coin Change
- Longest Increasing Subsequence
- Longest Common Subsequence
- Word Break Problem
- Combination Sum
- House Robber
- House Robber II
- Decode Ways
- Unique Paths
- Jump Game
- Clone Graph
- Course Schedule
- Pacific Atlantic Water Flow
- Number of Islands
- Longest Consecutive Sequence
- Alien Dictionary (Leetcode Premium)
- Graph Valid Tree (Leetcode Premium)
- Number of Connected Components in an Undirected Graph (Leetcode Premium)
- Insert Interval
- Merge Intervals
- Non-overlapping Intervals
- Meeting Rooms (Leetcode Premium)
- Meeting Rooms II (Leetcode Premium)
- Reverse a Linked List
- Detect Cycle in a Linked List
- Merge Two Sorted Lists
- Merge K Sorted Lists
- Remove Nth Node From End Of List
- Reorder List
- Longest Substring Without Repeating Characters
- Longest Repeating Character Replacement
- Minimum Window Substring
- Valid Anagram
- Group Anagrams
- Valid Parentheses
- Valid Palindrome
- Longest Palindromic Substring
- Palindromic Substrings
- Encode and Decode Strings (Leetcode Premium)
- Maximum Depth of Binary Tree
- Same Tree
- Invert/Flip Binary Tree
- Binary Tree Maximum Path Sum
- Binary Tree Level Order Traversal
- Serialize and Deserialize Binary Tree
- Subtree of Another Tree
- Construct Binary Tree from Preorder and Inorder Traversal
- Validate Binary Search Tree
- Kth Smallest Element in a BST
- Lowest Common Ancestor of BST
- Implement Trie (Prefix Tree)
- Add and Search Word
- Word Search II