The Blind 75 is a curated list of LeetCode problems created by Yangshun Tay, an engineer who was active on Blind (the anonymous professional network). The idea is simple: instead of grinding 500+ random problems, focus on 75 that cover the most important patterns.

This list has helped thousands of engineers land offers at Google, Meta, Amazon, and other top companies. I used it myself when preparing for interviews, and it's the most efficient way I've found to prepare for coding interviews.

Blind 75 Quick Stats

Total Problems

75 carefully selected

Time to Complete

4-8 weeks (2-3 hours/day)

Topics Covered

15 core patterns

Difficulty Mix

Easy: 15, Medium: 45, Hard: 15

Why Blind 75 Works

Quality Over Quantity

Pattern recognition: 75 problems that teach you the most common patterns, not obscure tricks
Interview relevance: These problems (or variations) frequently appear in real interviews
Time efficient: 4-8 weeks vs. months of random grinding
Confidence building: Finishing a defined list feels achievable

The Categories

Array (9 problems)

Foundation of everything. 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.

Time: 3-4 days | Key patterns: Two pointers, sliding window, prefix sums

Binary (5 problems)

Bit manipulation basics. Sum of Two Integers, Number of 1 Bits, Counting Bits, Missing Number, Reverse Bits.

Time: 1-2 days | Key patterns: XOR tricks, bit counting

Dynamic Programming (11 problems)

The category that scares people most. Climbing Stairs, Coin Change, Longest Increasing Subsequence, Longest Common Subsequence, Word Break, Combination Sum, House Robber I & II, Decode Ways, Unique Paths, Jump Game.

Time: 5-7 days | Key patterns: 1D DP, 2D DP, state machines

Graph (8 problems)

Critical for system design discussions too. Clone Graph, Course Schedule, Pacific Atlantic Water Flow, Number of Islands, Longest Consecutive Sequence, Alien Dictionary, Graph Valid Tree, Number of Connected Components.

Time: 4-5 days | Key patterns: BFS, DFS, Union Find, topological sort

Interval (5 problems)

Surprisingly common. Insert Interval, Merge Intervals, Non-overlapping Intervals, Meeting Rooms I & II.

Time: 2 days | Key patterns: Sorting, greedy, sweep line

Linked List (6 problems)

Classic interview favorite. Reverse a Linked List, Detect Cycle, Merge Two Sorted Lists, Merge K Sorted Lists, Remove Nth Node From End, Reorder List.

Time: 2-3 days | Key patterns: Fast/slow pointers, dummy head

Matrix (4 problems)

2D array mastery. Set Matrix Zeroes, Spiral Matrix, Rotate Image, Word Search.

Time: 2 days | Key patterns: In-place modification, DFS on grids

String (8 problems)

Always on interviews. Longest Substring Without Repeating Characters, Longest Repeating Character Replacement, Minimum Window Substring, Valid Anagram, Group Anagrams, Valid Parentheses, Valid Palindrome, Longest Palindromic Substring.

Time: 3-4 days | Key patterns: Sliding window, hash maps, two pointers

Tree (14 problems)

The largest category. Maximum Depth, Same Tree, Invert Binary Tree, Binary Tree Maximum Path Sum, Level Order Traversal, Serialize/Deserialize, Subtree of Another Tree, BST Lowest Common Ancestor, BST Kth Smallest, Validate BST, Implement Trie, Add/Search Word, Word Search II.

Time: 5-6 days | Key patterns: Recursion, BFS, DFS, Trie

Heap (3 problems)

Priority queue essentials. Merge K Sorted Lists, Top K Frequent Elements, Find Median from Data Stream.

Time: 1-2 days | Key patterns: Min/max heap, two heaps

Recommended Study Order

Week-by-Week Plan

Week 1

Arrays & Strings

Start here. These patterns appear everywhere. ~17 problems.

Week 2

Linked Lists & Binary

Classic data structure manipulation. ~11 problems.

Week 3

Trees & Tries

Recursion practice. Take your time. ~14 problems.

Week 4

Graphs

BFS, DFS, Union Find. ~8 problems.

Week 5

Dynamic Programming

The boss level. Go slow, understand each solution. ~11 problems.

Week 6

Intervals, Matrix, Heap

Cleanup week. ~12 problems.

Week 7-8

Review & Revisit

Redo problems you struggled with. Time yourself.

How to Actually Study

The Right Approach

1
Attempt first (15-20 min)
Struggle is learning. Don't look at solutions immediately.
2
Study the solution (if stuck)
Understand why it works. Don't just memorize code.
3
Implement from scratch
Close the solution. Code it yourself. This is where learning happens.
4
Explain out loud
Practice articulating your approach. Interviews require communication.
5
Revisit after 3 days
Spaced repetition. Can you still solve it without hints?

Practice Explaining Your Solutions

Coding is only half the battle. Craqly helps you practice articulating your approach in real-time, just like in actual interviews.

Common Mistakes

What Not to Do

✗ Rushing through problems — Speed comes from understanding, not memorization
✗ Looking at solutions too quickly — Struggle builds pattern recognition
✗ Skipping easy problems — They build foundations for harder ones
✗ Only solving, never reviewing — You'll forget without spaced repetition
✗ Ignoring time complexity — Always analyze Big O

The Bottom Line

The Blind 75 works because it's focused. Instead of randomly solving problems and hoping you hit the right patterns, you systematically cover the patterns that actually appear in interviews.

Give it 6-8 weeks of focused effort. By the end, you won't have memorized 75 solutions—you'll have internalized the patterns that let you solve problems you've never seen before.

The Core 75: Essential Coding Interview Problems & Study Strategy 2026