What the Blind 75 is
The Blind 75 is a list of 75 LeetCode problems first shared on the Blind forum as the shortest path through the patterns that coding interviews keep returning to: two pointers, sliding window, binary search, BFS and DFS, dynamic programming, intervals, heaps and tries. It is not the most problems you can do, but the most coverage per problem.
This page lists all 75 in the list’s usual ten groups, with the LeetCode number and difficulty. Every problem links to a full write-up on this site: each one explains the approaches, walks through complexity, and gives code in Python, Java, Go, JavaScript and C#, and C++ on the newest pages.
Coverage: all 75 problems have a full solution on this site.
How to work through it
- Go group by group, not in random order. Each group teaches one family of patterns, and later problems in a group reuse earlier ideas.
- Do the Easy problems first in each group, then the Mediums. Leave the Hard ones (Merge k Sorted Lists, Minimum Window Substring, Alien Dictionary, Serialize and Deserialize Binary Tree, Word Search II) until the pattern feels natural.
- Time-box each attempt to 25-30 minutes. If you’re stuck, read the approach, close it, and write the solution again from memory the next day.
- Say the complexity out loud before you code. Interviewers care about why an approach is O(n log n) as much as about the code.
- Plan for 6-8 weeks at about 10 problems a week. Revisit any problem you couldn’t solve cleanly a week later.
Array
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Two Sum | 1 | Easy |
| 2 | Best Time to Buy and Sell Stock | 121 | Easy |
| 3 | Contains Duplicate | 217 | Easy |
| 4 | Product of Array Except Self | 238 | Medium |
| 5 | Maximum Subarray | 53 | Medium |
| 6 | Maximum Product Subarray | 152 | Medium |
| 7 | Find Minimum in Rotated Sorted Array | 153 | Medium |
| 8 | Search in Rotated Sorted Array | 33 | Medium |
| 9 | 3Sum | 15 | Medium |
| 10 | Container With Most Water | 11 | Medium |
Binary
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Sum of Two Integers | 371 | Medium |
| 2 | Number of 1 Bits | 191 | Easy |
| 3 | Counting Bits | 338 | Easy |
| 4 | Missing Number | 268 | Easy |
| 5 | Reverse Bits | 190 | Easy |
Dynamic Programming
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Climbing Stairs | 70 | Easy |
| 2 | Coin Change | 322 | Medium |
| 3 | Longest Increasing Subsequence | 300 | Medium |
| 4 | Longest Common Subsequence | 1143 | Medium |
| 5 | Word Break | 139 | Medium |
| 6 | Combination Sum IV | 377 | Medium |
| 7 | House Robber | 198 | Medium |
| 8 | House Robber II | 213 | Medium |
| 9 | Decode Ways | 91 | Medium |
| 10 | Unique Paths | 62 | Medium |
| 11 | Jump Game | 55 | Medium |
Graph
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Clone Graph | 133 | Medium |
| 2 | Course Schedule | 207 | Medium |
| 3 | Pacific Atlantic Water Flow | 417 | Medium |
| 4 | Number of Islands | 200 | Medium |
| 5 | Longest Consecutive Sequence | 128 | Medium |
| 6 | Alien Dictionary | 269 | Hard |
| 7 | Graph Valid Tree | 261 | Medium |
| 8 | Number of Connected Components in an Undirected Graph | 323 | Medium |
Interval
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Insert Interval | 57 | Medium |
| 2 | Merge Intervals | 56 | Medium |
| 3 | Non-overlapping Intervals | 435 | Medium |
| 4 | Meeting Rooms | 252 | Easy |
| 5 | Meeting Rooms II | 253 | Medium |
Linked List
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Reverse Linked List | 206 | Easy |
| 2 | Linked List Cycle | 141 | Easy |
| 3 | Merge Two Sorted Lists | 21 | Easy |
| 4 | Merge k Sorted Lists | 23 | Hard |
| 5 | Remove Nth Node From End of List | 19 | Medium |
| 6 | Reorder List | 143 | Medium |
Matrix
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Set Matrix Zeroes | 73 | Medium |
| 2 | Spiral Matrix | 54 | Medium |
| 3 | Rotate Image | 48 | Medium |
| 4 | Word Search | 79 | Medium |
String
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Longest Substring Without Repeating Characters | 3 | Medium |
| 2 | Longest Repeating Character Replacement | 424 | Medium |
| 3 | Minimum Window Substring | 76 | Hard |
| 4 | Valid Anagram | 242 | Easy |
| 5 | Group Anagrams | 49 | Medium |
| 6 | Valid Parentheses | 20 | Easy |
| 7 | Valid Palindrome | 125 | Easy |
| 8 | Longest Palindromic Substring | 5 | Medium |
| 9 | Palindromic Substrings | 647 | Medium |
| 10 | Encode and Decode Strings | 271 | Medium |
Tree
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Maximum Depth of Binary Tree | 104 | Easy |
| 2 | Same Tree | 100 | Easy |
| 3 | Invert Binary Tree | 226 | Easy |
| 4 | Binary Tree Maximum Path Sum | 124 | Hard |
| 5 | Binary Tree Level Order Traversal | 102 | Medium |
| 6 | Serialize and Deserialize Binary Tree | 297 | Hard |
| 7 | Subtree of Another Tree | 572 | Easy |
| 8 | Construct Binary Tree from Preorder and Inorder Traversal | 105 | Medium |
| 9 | Validate Binary Search Tree | 98 | Medium |
| 10 | Kth Smallest Element in a BST | 230 | Medium |
| 11 | Lowest Common Ancestor of a BST | 235 | Medium |
| 12 | Implement Trie (Prefix Tree) | 208 | Medium |
| 13 | Design Add and Search Words Data Structure | 211 | Medium |
| 14 | Word Search II | 212 | Hard |
Heap
| # | Problem | LeetCode | Difficulty |
|---|---|---|---|
| 1 | Merge k Sorted Lists | 23 | Hard |
| 2 | Top K Frequent Elements | 347 | Medium |
| 3 | Find Median from Data Stream | 295 | Hard |
Merge k Sorted Lists appears in both the Linked List and Heap groups; it counts once.
After the Blind 75
- For a company-specific plan, see the FAANG coding interview prep plan and the Google, Meta and Amazon plans.
- For system design rounds, follow the system design interview plan.
- For more practice by pattern, browse all coding problems.