Blind 75

The Blind 75 is a curated list of 75 essential LeetCode coding problems designed to prepare software engineers for technical interviews at top tech companies.

Video walkthroughs

• Contains Duplicate - LeetCode 217: Remember What You've Seen in One Pass (Python & Java) (4:50)
• Valid Anagram - LeetCode 242: Count Up, Count Down, Cancel Out (Python & Java) (4:48)
• Two Sum - LeetCode 1: Look Up What's Missing in One Pass (Python & Java) (4:59)
• Group Anagrams - LeetCode 49: Sort Each Word Into a Key (Python & Java) (5:00)
• Top K Frequent Elements - LeetCode 347: Can You Beat O(n log n)? (Python & Java) (5:07)
• Encode and Decode Strings - LeetCode 271: Why Joining with a Separator Breaks (Python & Java) (5:03)
• Product of Array Except Self - LeetCode 238: Why Division Breaks on a Zero (Python & Java) (5:11)
• Longest Consecutive Sequence - LeetCode 128: Count Only From the Start of a Run (Python & Java) (4:59)
• Valid Palindrome - LeetCode 125: Check It Without Copying the String (Python & Java) (4:58)
• 3Sum - LeetCode 15: No Duplicate Triplets, No Hash Set (Python & Java) (5:57)
• Container With Most Water - LeetCode 11 - Two Pointers (Python & Java) (5:39)
• Best Time to Buy and Sell Stock - LeetCode 121 - Sliding Window (Python & Java) (5:12)
• Longest Substring Without Repeating Characters - LeetCode 3 - Sliding Window (Python & Java) (5:37)
• Longest Repeating Character Replacement - LeetCode 424 - Sliding Window (Python & Java) (5:55)
• Minimum Window Substring - LeetCode 76 - Sliding Window (Python & Java) (6:24)
• Valid Parentheses - LeetCode 20: One Stack, Three Ways to Return False (Python & Java) (5:38)
• Find Minimum in Rotated Sorted Array - LeetCode 153: Binary Search for the Drop (Python & Java) (5:16)
• Search in Rotated Sorted Array - LeetCode 33: Which Half Is Sorted? (Python & Java) (5:51)
• Reverse Linked List - LeetCode 206: Three Pointers, One Pass (Python & Java) (4:41)
• Merge Two Sorted Lists - LeetCode 21: Dummy Node and a Tail Pointer (Python & Java) (5:28)
• Linked List Cycle - LeetCode 141: Why Fast Always Catches Slow (Floyd's, Python & Java) (5:08)
• Reorder List - LeetCode 143: Split, Reverse, Weave in O(1) Space (Python & Java) (5:39)
• Remove Nth Node From End of List - LeetCode 19: One Pass with a Dummy Node (Python & Java) (5:01)
• Merge K Sorted Lists - LeetCode 23: Heap + Dummy Node, Explained Visually (Python & Java) (5:39)
• Invert Binary Tree - LeetCode 226: Swap Every Node's Children, Explained Visually (Python & Java) (4:52)
• Maximum Depth of Binary Tree - LeetCode 104: 1 + Max(Left, Right) Explained Visually (Python & Java) (4:57)
• Same Tree - LeetCode 100: Check Both Pairs of Subtrees, Explained Visually (Python & Java) (5:21)
• Subtree of Another Tree - LeetCode 572: Same Tree, Tried at Every Node (Python & Java) (6:14)
• Lowest Common Ancestor of a Binary Search Tree - LeetCode 235: One Walk Down, O(h) (Python & Java) (5:35)
• Binary Tree Level Order Traversal - LeetCode 102: BFS, One Level at a Time (Python & Java) (5:56)
• Validate Binary Search Tree - LeetCode 98: Min/Max Bounds DFS, Explained Visually (Python & Java) (6:12)
• Kth Smallest Element in a BST - LeetCode 230: Inorder Stack Walk, Explained Visually (Python & Java) (5:58)
• Construct Binary Tree from Preorder and Inorder Traversal - LeetCode 105: Split It (Python & Java) (6:25)
• Binary Tree Maximum Path Sum - LeetCode 124: Join Both Sides, Hand Up One (Python & Java) (6:35)
• Serialize and Deserialize Binary Tree - LeetCode 297: Write It Out, Build It Back (Python & Java) (6:03)
• Find Median from Data Stream - LeetCode 295: Two Heaps, Smaller Half and Larger Half (Python & Java) (6:15)
• Combination Sum - LeetCode 39: Backtracking, Use It Again or Step Back (Python & Java) (6:19)
• Word Search - LeetCode 79: Depth-First Search, Mark Cells, Unmark on the Way Back (Python & Java) (6:32)
• Implement Trie (Prefix Tree) - LeetCode 208: A Path of Letters, Mark Where Words End (Python & Java) (5:57)
• Design Add and Search Words Data Structure - LeetCode 211: A Dot Tries Every Child (Python & Java) (6:31)
• Word Search II - LeetCode 212: Trie + DFS, Cut Branches As You Go (Python & Java) (7:18)
• Number of Islands - LeetCode 200: Sink Each Island As You Find It (Python & Java) (6:04)
• Clone Graph - LeetCode 133: Copy Every Node Once With a Hash Map (Python & Java) (6:19)
• Pacific Atlantic Water Flow - LeetCode 417: Climb Up From Both Oceans (Python & Java) (7:38)
• Course Schedule - LeetCode 207: Find the Cycle With a Queue (Python & Java) (6:00)
• Graph Valid Tree - LeetCode 261: Union Find Explained (Python & Java) (6:07)
• Number of Connected Components - LeetCode 323: Union Find Explained (Python & Java) (5:37)
• Alien Dictionary - LeetCode 269 Explained: Find the Letter Order (Python & Java) (6:43)
• Climbing Stairs - LeetCode 70: Your First DP Table (Python & Java) (4:45)
• House Robber - LeetCode 198: Rob It or Skip It (Python & Java) (5:10)
• House Robber II - LeetCode 213: Houses in a Circle (Python & Java) (6:35)
• Longest Palindromic Substring - LeetCode 5: Grow From Every Center (Python & Java) (5:51)
• Palindromic Substrings - LeetCode 647: Count Every Palindrome (Python & Java) (6:01)
• Decode Ways - LeetCode 91: One Digit or Two (Python & Java) (5:57)
• Coin Change - LeetCode 322: Try Every Coin Last (Python & Java) (6:00)
• Maximum Product Subarray - LeetCode 152: Keep the Biggest and Smallest (Python & Java) (5:20)
• Word Break - LeetCode 139: Mark Where Each Word Ends (Python & Java) (5:32)
• Longest Increasing Subsequence - LeetCode 300: Why the Last Value Lies (Python & Java) (5:23)
• Unique Paths - LeetCode 62: Above Plus Left, the First 2-D DP (Python & Java) (5:41)
• Longest Common Subsequence - LeetCode 1143: Match Goes Diagonal, Else Keep the Max (Python & Java) (6:36)
• Maximum Subarray - LeetCode 53: Drop the Running Sum When It Goes Negative (Python & Java) (5:36)
• Jump Game - LeetCode 55: If an Index Is Past Your Reach, You're Stuck (Python & Java) (5:35)
• Insert Interval - LeetCode 57: Merge Everything It Overlaps in One Pass (Python & Java) (6:11)
• Merge Intervals - LeetCode 56: Sort Once, Merge Every Overlap (Python & Java) (6:04)
• Non-overlapping Intervals - LeetCode 435: Sort by End, Keep the Most (Python & Java) (5:45)
• Meeting Rooms - LeetCode 252: Can You Attend Every Meeting? (Python & Java) (5:13)
• Meeting Rooms II - LeetCode 253: How Many Rooms Do You Need? (Python & Java) (6:08)
• Rotate Image - LeetCode 48: Rotate a Matrix In Place (Python & Java) (5:23)
• Spiral Matrix - LeetCode 54: Walk a Matrix in Spiral Order (Python & Java) (5:49)
• Set Matrix Zeroes - LeetCode 73: O(1) Space In Place (Python & Java) (5:19)
• Number of 1 Bits - LeetCode 191: The n & (n - 1) Trick (Python & Java) (4:57)
• Counting Bits - LeetCode 338: Reuse Half the Answer (Python & Java) (4:58)
• Reverse Bits - LeetCode 190: Shift Out, Shift In (Python & Java) (5:26)
• Missing Number - LeetCode 268: O(1) Space with XOR (Python & Java) (5:16)
• Sum of Two Integers - LeetCode 371: XOR Is the Sum, AND Is the Carry (Python & Java) (5:18)

All 75 problems

1. Contains Duplicate Easy
2. Valid Anagram Easy
3. Two Sum Easy
4. Group Anagrams Medium
5. Top K Frequent Elements Medium
6. Encode and Decode Strings Medium
7. Product of Array Except Self Medium
8. Longest Consecutive Sequence Medium
9. Valid Palindrome Easy
10. 3Sum Medium
11. Container With Most Water Medium
12. Best Time to Buy and Sell Stock Easy
13. Longest Substring Without Repeating Characters Medium
14. Longest Repeating Character Replacement Medium
15. Minimum Window Substring Hard
16. Valid Parentheses Easy
17. Find Minimum in Rotated Sorted Array Medium
18. Search in Rotated Sorted Array Medium
19. Reverse Linked List Easy
20. Merge Two Sorted Lists Easy
21. Linked List Cycle Easy
22. Reorder List Medium
23. Remove Nth Node From End of List Medium
24. Merge K Sorted Lists Hard
25. Invert Binary Tree Easy
26. Maximum Depth of Binary Tree Easy
27. Same Tree Easy
28. Subtree of Another Tree Easy
29. Lowest Common Ancestor of a Binary Search Tree Medium
30. Binary Tree Level Order Traversal Medium
31. Validate Binary Search Tree Medium
32. Kth Smallest Element in a BST Medium
33. Construct Binary Tree from Preorder and Inorder Traversal Medium
34. Binary Tree Maximum Path Sum Hard
35. Serialize and Deserialize Binary Tree Hard
36. Find Median from Data Stream Hard
37. Combination Sum Medium
38. Word Search Medium
39. Implement Trie (Prefix Tree) Medium
40. Design Add and Search Words Data Structure Medium
41. Word Search II Hard
42. Number of Islands Medium
43. Clone Graph Medium
44. Pacific Atlantic Water Flow Medium
45. Course Schedule Medium
46. Graph Valid Tree Medium
47. Number of Connected Components in an Undirected Graph Medium
48. Alien Dictionary Hard
49. Climbing Stairs Easy
50. House Robber Medium
51. House Robber II Medium
52. Longest Palindromic Substring Medium
53. Palindromic Substrings Medium
54. Decode Ways Medium
55. Coin Change Medium
56. Maximum Product Subarray Medium
57. Word Break Medium
58. Longest Increasing Subsequence Medium
59. Unique Paths Medium
60. Longest Common Subsequence Medium
61. Maximum Subarray Medium
62. Jump Game Medium
63. Insert Interval Medium
64. Merge Intervals Medium
65. Non Overlapping Intervals Medium
66. Meeting Rooms Easy
67. Meeting Rooms II Medium
68. Rotate Image Medium
69. Spiral Matrix Medium
70. Set Matrix Zeroes Medium
71. Number of 1 Bits Easy
72. Counting Bits Easy
73. Reverse Bits Easy
74. Missing Number Easy
75. Sum of Two Integers Medium

Mock interview