Blind 75 LeetCode Questions

LeetCode is a popular platform for practicing coding problems, especially when preparing for technical interviews. The "Blind 75" is a collection of 75 carefully selected questions from LeetCode that are particularly useful for interview preparation. These questions cover a range of topics and difficulty levels, and they are chosen based on their frequency and importance in real interviews.

This collection is divided into several categories, such as arrays, strings, linked lists, trees, dynamic programming, and more. Each category contains a mix of easy, medium, and hard problems, allowing you to gradually build your skills.

Array

• Two Sum <span style={{color: 'green'}}>(Easy)</span> HashMap Solution
• Best Time to Buy and Sell Stock <span style={{color: 'green'}}>(Easy)</span> Two Pointer Solution
• Contains Duplicate <span style={{color: 'green'}}>(Easy)</span> HashSet Solution
• Product of Array Except Self <span style={{color: 'orange'}}>(Medium)</span> Prefix and Suffix product array Solution
• Maximum Subarray <span style={{color: 'orange'}}>(Medium)</span> Kadane's algorithm (Dynamic Programming) Solution
• Maximum Product Subarray <span style={{color: 'orange'}}>(Medium)</span> Kadane's algorithm (Dynamic Programming) Solution
• Find Minimum in Rotated Sorted Array <span style={{color: 'orange'}}>(Medium)</span> Binary Search Solution
• Search in Rotated Sorted Array <span style={{color: 'orange'}}>(Medium)</span> Binary Search Solution
• 3Sum <span style={{color: 'orange'}}>(Medium)</span> Two Pointer Solution
• Container With Most Water <span style={{color: 'orange'}}>(Medium)</span> Two Pointer Solution

Binary

• Sum of Two Integers <span style={{color: 'orange'}}>(Medium)</span> Bit Manipulation Solution
• Number of 1 Bits <span style={{color: 'green'}}>(Easy)</span> Bit Manipulation Solution
• Counting Bits <span style={{color: 'green'}}>(Easy)</span> Bit Manipulation (Dynamic Programming) Solution
• Missing Number <span style={{color: 'green'}}>(Easy)</span> Bit Manipulation Solution
• Reverse Bits <span style={{color: 'green'}}>(Easy)</span> Bit Manipulation Solution

Dynamic Programming

• Climbing Stairs <span style={{color: 'green'}}>(Easy)</span> Dynamic Programming Solution
• Coin Change <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Longest Increasing Subsequence <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Longest Common Subsequence <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Word Break Problem <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Combination Sum <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• House Robber <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• House Robber II <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Decode Ways <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Unique Paths <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution
• Jump Game <span style={{color: 'orange'}}>(Medium)</span> Dynamic Programming Solution

Graph

• Clone Graph <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution
• Course Schedule <span style={{color: 'orange'}}>(Medium)</span> Topological Sort Solution
• Pacific Atlantic Water Flow <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution
• Number of Islands <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution
• Longest Consecutive Sequence <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution
• Alien Dictionary (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> Topological Sort Solution
• Graph Valid Tree (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution
• Number of Connected Components in an Undirected Graph (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> Graph Traversal Solution

Interval

• Insert Interval <span style={{color: 'orange'}}>(Medium)</span> Interval Solution
• Merge Intervals <span style={{color: 'orange'}}>(Medium)</span> Interval Solution
• Non-overlapping Intervals <span style={{color: 'orange'}}>(Medium)</span> Interval Solution
• Meeting Rooms (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> Interval Solution
• Meeting Rooms II (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> Interval Solution

Linked List

• Reverse a Linked List <span style={{color: 'green'}}>(Easy)</span> Linked List Solution
• Detect Cycle in a Linked List <span style={{color: 'green'}}>(Easy)</span> Linked List Two Pointers Solution
• Merge Two Sorted Lists <span style={{color: 'green'}}>(Easy)</span> Linked List Solution
• Merge K Sorted Lists <span style={{color: 'red'}}>(Hard)</span> Linked List Divide and Conquer Solution
• Remove Nth Node From End Of List <span style={{color: 'orange'}}>(Medium)</span> Linked List Solution
• Reorder List <span style={{color: 'orange'}}>(Medium)</span> Linked List Solution

Matrix

• Set Matrix Zeroes <span style={{color: 'green'}}>(Easy)</span> Matrix Solution
• Spiral Matrix <span style={{color: 'orange'}}>(Medium)</span> Matrix right,left,top,bottom Solution
• Rotate Image <span style={{color: 'orange'}}>(Medium)</span> Matrix change rows with columns then rotate each row Solution
• Word Search <span style={{color: 'orange'}}>(Medium)</span> Matrix DFS Solution

String

• Longest Substring Without Repeating Characters <span style={{color: 'orange'}}>(Medium)</span> Sliding Window Solution
• Longest Repeating Character Replacement <span style={{color: 'orange'}}>(Medium)</span> Sliding Window Solution
• Minimum Window Substring <span style={{color: 'red'}}>(Hard)</span> Sliding Window Solution
• Valid Anagram <span style={{color: 'green'}}>(Easy)</span> HashMap Solution
• Group Anagrams <span style={{color: 'orange'}}>(Medium)</span> HashMap Solution
• Valid Parentheses <span style={{color: 'green'}}>(Easy)</span> Stack Solution
• Valid Palindrome <span style={{color: 'green'}}>(Easy)</span> Two Pointer Solution
• Longest Palindromic Substring <span style={{color: 'orange'}}>(Medium)</span> Two Pointer expand around center Solution
• Palindromic Substrings <span style={{color: 'orange'}}>(Medium)</span> Two Pointer Solution
• Encode and Decode Strings (Leetcode Premium) <span style={{color: 'orange'}}>(Medium)</span> String Solution

Tree

• Maximum Depth of Binary Tree <span style={{color: 'green'}}>(Easy)</span> Tree Traversal Solution
• Same Tree <span style={{color: 'green'}}>(Easy)</span> Tree Traversal Solution
• Invert/Flip Binary Tree <span style={{color: 'green'}}>(Easy)</span> Tree Traversal Solution
• Binary Tree Maximum Path Sum <span style={{color: 'red'}}>(Hard)</span> Tree Traversal Solution
• Binary Tree Level Order Traversal <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Serialize and Deserialize Binary Tree <span style={{color: 'red'}}>(Hard)</span> Tree Traversal Solution
• Subtree of Another Tree <span style={{color: 'green'}}>(Easy)</span> Tree Traversal Solution
• Construct Binary Tree from Preorder and Inorder Traversal <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Validate Binary Search Tree <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Kth Smallest Element in a BST <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Lowest Common Ancestor of BST <span style={{color: 'oragne'}}>(Medium)</span> Tree Traversal Solution
• Implement Trie (Prefix Tree) <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Add and Search Word <span style={{color: 'orange'}}>(Medium)</span> Tree Traversal Solution
• Word Search II <span style={{color: 'red'}}>(Hard)</span> Tree Traversal Solution

Heap

• Merge K Sorted Lists <span style={{color: 'red'}}>(Hard)</span> Heap Solution
• Top K Frequent Elements <span style={{color: 'orange'}}>(Medium)</span> Heap Solution
• Find Median from Data Stream <span style={{color: 'red'}}>(Hard)</span> Heap Solution

Important Link:

14 Patterns to Ace Any Coding Interview Question

How to Use This List

• Start with Basics: Begin with easier problems to build your confidence.
• Focus on Patterns: Identify common patterns and algorithms.
• Practice Regularly: Consistency is key in problem-solving.
• Review Solutions: Understand not just the how, but also the why behind each solution.
• Mock Interviews: Use these problems to simulate real interview scenarios.

Resources

• LeetCode
• Blind 75 Discussion Forum
• Coding Interview Resources
• LeetCode Patterns
• LeetCode Explore
• Blind 75 spreadsheet
• Coding Patterns

Remember, the goal is not just to solve all 75 problems, but to understand the underlying principles and patterns that will enable you to tackle any new problem with confidence.