1 Merge Intervals Array Sorting
Medium 100
0.5% 2 Find Followers Count Database
Easy 94
0.7% 3 Minimum Changes To Make Alternating Binary String String
Easy 94
0.7% 4 Best Time to Buy and Sell Stock Array Dynamic Programming
Easy 91
0.6% 5 Number of Islands Array Depth-First Search Breadth-First Search Union-Find Matrix
Medium 91
0.6% 6 Basic Calculator II Math String Stack
Medium 91
0.5% 7 Design Circular Queue Array Linked List Design Queue
Medium 85
0.5% 8 Building H2O Concurrency
Medium 85
0.6% 9 Longest Substring Without Repeating Characters Hash Table String Sliding Window
Medium 81
0.4% 10 Reorganize String Hash Table String Greedy Sorting Heap (Priority Queue) Counting
Medium 81
0.6% 11 Trapping Rain Water Array Two Pointers Dynamic Programming Stack Monotonic Stack
Hard 81
0.7% 12 Valid Parentheses String Stack
Easy 76
0.4% 13 Rectangle Area Math Geometry
Medium 76
0.5% 14 Letter Combinations of a Phone Number Hash Table String Backtracking
Medium 71
0.7% 15 3Sum Array Two Pointers Sorting
Medium 71
0.4% 16 LRU Cache Hash Table Linked List Design Doubly-Linked List
Medium 71
0.5% 17 Two Sum Array Hash Table
Easy 71
0.6% 18 Top K Frequent Elements Array Hash Table Divide and Conquer Sorting Heap (Priority Queue) Bucket Sort Counting Quickselect
Medium 64
0.7% 19 Maximum Subarray Array Divide and Conquer Dynamic Programming
Medium 64
0.5% 20 Shortest Bridge Array Depth-First Search Breadth-First Search Matrix
Medium 64
0.6% 21 Evaluate Division Array String Depth-First Search Breadth-First Search Union-Find Graph Theory Shortest Path
Medium 64
0.6% 22 Word Ladder Hash Table String Breadth-First Search
Hard 64
0.5% 23 Snakes and Ladders Array Breadth-First Search Matrix
Medium 64
0.5% 24 Container With Most Water Array Two Pointers Greedy
Medium 54
0.6% 25 Design Tic-Tac-Toe Array Hash Table Design Matrix Simulation
Medium 54
0.6% 26 Valid Anagram Hash Table String Sorting
Easy 54
0.7% 27 First Missing Positive Array Hash Table
Hard 54
0.4% 28 Longest Consecutive Sequence Array Hash Table Union-Find
Medium 54
0.5% 29 Course Schedule Depth-First Search Breadth-First Search Graph Theory Topological Sort
Medium 54
0.5% 30 Rotate Image Array Math Matrix
Medium 54
0.8% 31 Evaluate Reverse Polish Notation Array Math Stack
Medium 54
0.6% 32 Happy Number Hash Table Math Two Pointers
Easy 54
0.6% 33 UTF-8 Validation Array Bit Manipulation
Medium 54
0.5% 34 Design Parking System Design Simulation Counting
Easy 54
0.9% 35 Word Ladder II Hash Table String Backtracking Breadth-First Search
Hard 54
0.3% 36 Design Memory Allocator Array Hash Table Design Simulation
Medium 54
0.5% 37 Find All Possible Recipes from Given Supplies Array Hash Table String Graph Theory Topological Sort
Medium 54
0.6% 38 Median of Two Sorted Arrays Array Binary Search Divide and Conquer
Hard 54
0.5% 39 Is Subsequence Two Pointers String Dynamic Programming
Easy 54
0.5% 40 Flatten Nested List Iterator Stack Tree Depth-First Search Design Queue Iterator
Medium 54
0.7% 41 Logger Rate Limiter Hash Table Design Data Stream
Easy 54
0.8%