Blind 75

A curated list of 75 essential coding problems for technical interviews.

75 problems•9 sections

Difficulty

Problem	Difficulty	Video
Two Sum	easy
Valid Parentheses	easy
Best Time To Buy And Sell Stock 1 - only one transaction	easy
Valid Palindrome	easy
Contains Duplicate 1 - Check if array has duplicates	easy
Valid Anagram	easy
Longest Substring Without Repeating Characters	medium
Longest Palindromic Substring	medium
Container With Most Water	medium
3Sum0 - Find three elements in an array that sum to a zero	medium
Search in Rotated Sorted Array	medium
Group Anagrams	medium
Maximum Subarray Sum	medium
Maximum Product Subarray	medium
Find Minimum in Rotated Sorted Array	medium
Product of Array Except Self	medium
Encode and Decode Strings	medium
Longest Substring with Same Letters after Replacement	medium
Palindromic Substrings	medium
Minimum Window Substring	hard

Problem	Difficulty	Video
Merge Two Sorted Linked Lists	easy
Linked List Cycle 1 - Detect Cycle	easy
Reverse Linked List	easy
Remove Nth Node From End of List	medium
Reorder List such that i-th element points to n-i-th element	medium
Merge K Sorted Lists	hard

Problem	Difficulty	Video
Same Tree	easy
Maximum Depth of Binary Tree	easy
Invert Binary Tree	easy
Subtree of Another Tree	easy
Validate Binary Search Tree	medium
Binary Tree Level Order Traversal - Level by Level	medium
Construct Binary Tree from Inorder and Preorder Traversal	medium
Implement Trie	medium
Design Add and Search Words Data Structure	medium
Kth Smallest Element in a BST	medium
Lowest Common Ancestor of a Binary Search Tree	medium
Binary Tree Path Sum - Maximum between any two nodes	hard
Word Search 2 - Return All Words	hard
Serialize and Deserialize Binary Tree	hard

Problem	Difficulty	Video
Top K Frequent Elements	medium
Find Median from Data Stream	hard

Problem	Difficulty	Video
Longest Consecutive Sequence	medium
Clone Undirected Graph	medium
Number of Islands	medium
Course Schedule 1 - Is it Possible	medium
Graph Valid Tree	medium
Number of Connected Components in an Undirected Graph	medium	-
Pacific Atlantic Water Flow	medium
Alien Dictionary	hard

Problem	Difficulty	Video
Climbing Stairs - Take atmost 2 Steps	easy
Combination Sum 1	medium
Jump Game 1 - Check if it reaches last index	medium
Unique Paths in Grid 1 - Count all paths moving right or down	medium
Decode Ways	medium
Word Break 1 - Check if word is breakable	medium
House Robber	medium
House Robber 2 - Houses in circle	medium
Longest Increasing Subsequence	medium
Coin Change with Fewest Number of Coins Given Infinite Supply	medium
Longest Common Subsequence LCS 1 - Get Length	medium

Problem	Difficulty	Video
Meeting Rooms 1 - Can person attend all meetings	easy
Merge Overlapping Intervals	medium
Insert Interval	medium
Maximum Intervals Overlap Count	medium
Non-overlapping Intervals	medium

Problem	Difficulty	Video
Rotate n x n matrix by 90 degrees	medium
Spiral Matrix 1 - Return	medium
Set Matrix Zeros	medium
Word Search 1 - Find if word exists	medium

Arrays & Hashing