1 Two Sum Array Hash Table
Easy 100
0.6% 2 Maximum Path Quality of a Graph Array Backtracking Graph Theory
Hard 92
0.6% 3 Count the Number of Infection Sequences Array Math Combinatorics
Hard 92
0.4% 4 Maximum Students Taking Exam Array Dynamic Programming Bit Manipulation Matrix Bitmask
Hard 92
0.5% 5 Movie Rating Database
Medium 92
0.4% 6 Count Increasing Quadruplets Array Dynamic Programming Binary Indexed Tree Enumeration Prefix Sum
Hard 92
0.3% 7 Container With Most Water Array Two Pointers Greedy
Medium 86
0.6% 8 Longest Common Prefix Array String Trie
Easy 79
0.5% 9 Valid Parentheses String Stack
Easy 79
0.4% 10 Best Time to Buy and Sell Stock Array Dynamic Programming
Easy 75
0.6% 11 Number of Islands Array Depth-First Search Breadth-First Search Union-Find Matrix
Medium 75
0.6% 12 Merge Intervals Array Sorting
Medium 75
0.5% 13 Maximum Subarray Array Divide and Conquer Dynamic Programming
Medium 69
0.5% 14 Longest Palindromic Substring Two Pointers String Dynamic Programming
Medium 69
0.4% 15 Palindrome Number Math
Easy 69
0.6% 16 Reverse Linked List Linked List Recursion
Easy 62
0.8% 17 Kth Largest Element in an Array Array Divide and Conquer Sorting Heap (Priority Queue) Quickselect
Medium 62
0.7% 18 Valid Palindrome Two Pointers String
Easy 62
0.5% 19 LRU Cache Hash Table Linked List Design Doubly-Linked List
Medium 62
0.5% 20 Leftmost Column with at Least a One Array Binary Search Matrix Interactive
Medium 62
0.6% 21 Coin Change Array Dynamic Programming Breadth-First Search
Medium 62
0.5% 22 Group Anagrams Array Hash Table String Sorting
Medium 62
0.7% 23 Move Zeroes Array Two Pointers
Easy 62
0.6% 24 Longest Substring Without Repeating Characters Hash Table String Sliding Window
Medium 62
0.4% 25 Linked List Cycle Hash Table Linked List Two Pointers
Easy 62
0.5% 26 Search a 2D Matrix Array Binary Search Matrix
Medium 62
0.5% 27 Maximal Square Array Dynamic Programming Matrix
Medium 53
0.5% 28 Valid Perfect Square Math Binary Search
Easy 53
0.5% 29 Trapping Rain Water Array Two Pointers Dynamic Programming Stack Monotonic Stack
Hard 53
0.7% 30 Binary Search Tree to Greater Sum Tree Tree Depth-First Search Binary Search Tree Binary Tree
Medium 53
0.9% 31 Candy Array Greedy
Hard 53
0.5% 32 Product of Array Except Self Array Prefix Sum
Medium 53
0.7% 33 Same Tree Tree Depth-First Search Breadth-First Search Binary Tree
Easy 53
0.7% 34 Search in Rotated Sorted Array Array Binary Search
Medium 53
0.5% 35 Count Primes Array Math Enumeration Number Theory
Medium 53
0.4% 36 Add Two Numbers Linked List Math Recursion
Medium 53
0.5% 37 Implement Queue using Stacks Stack Design Queue
Easy 53
0.7% 38 Lowest Common Ancestor of a Binary Tree Tree Depth-First Search Binary Tree
Medium 53
0.7% 39 Palindrome Linked List Linked List Two Pointers Stack Recursion
Easy 53
0.6% 40 Ransom Note Hash Table String Counting
Easy 53
0.7% 41 Daily Temperatures Array Stack Monotonic Stack
Medium 53
0.7% 42 Minimum Window Substring Hash Table String Sliding Window
Hard 53
0.5%