1 LRU Cache Hash Table Linked List Design Doubly-Linked List
Medium 100
0.5% 2 Two Sum Array Hash Table
Easy 98
0.6% 3 Maximum Depth of Binary Tree Tree Depth-First Search Breadth-First Search Binary Tree
Easy 98
0.8% 4 Reverse Linked List Linked List Recursion
Easy 98
0.8% 5 Contains Duplicate Array Hash Table Sorting
Easy 98
0.6% 6 Serialize and Deserialize Binary Tree String Tree Depth-First Search Breadth-First Search Design Binary Tree
Hard 98
0.6% 7 Largest Palindrome Product Math Enumeration
Hard 98
0.4% 8 Median of Two Sorted Arrays Array Binary Search Divide and Conquer
Hard 95
0.5% 9 Roman to Integer Hash Table Math String
Easy 95
0.7% 10 Word Break Array Hash Table String Dynamic Programming Trie Memoization
Medium 95
0.5% 11 Linked List Cycle Hash Table Linked List Two Pointers
Easy 95
0.5% 12 Peeking Iterator Array Design Iterator
Medium 95
0.6% 13 Non-decreasing Subsequences Array Hash Table Backtracking Bit Manipulation
Medium 95
0.6% 14 Maximum Distance in Arrays Array Greedy
Medium 95
0.5% 15 Binary Number with Alternating Bits Bit Manipulation
Easy 95
0.7% 16 Matrix Cells in Distance Order Array Math Geometry Sorting Matrix
Easy 95
0.7% 17 Top K Frequent Elements Array Hash Table Divide and Conquer Sorting Heap (Priority Queue) Bucket Sort Counting Quickselect
Medium 78
0.7% 18 Combination Sum Array Backtracking
Medium 65
0.8% 19 Palindrome Number Math
Easy 55
0.6% 20 Longest Common Prefix Array String Trie
Easy 55
0.5% 21 Valid Parentheses String Stack
Easy 55
0.4% 22 Search in Rotated Sorted Array Array Binary Search
Medium 55
0.5% 23 Spiral Matrix Array Matrix Simulation
Medium 55
0.6% 24 Validate Binary Search Tree Tree Depth-First Search Binary Search Tree Binary Tree
Medium 55
0.4% 25 Decode String String Stack Recursion
Medium 55
0.6% 26 Longest Repeating Character Replacement Hash Table String Sliding Window
Medium 55
0.6% 27 Subarray Sum Equals K Array Hash Table Prefix Sum
Medium 55
0.5% 28 Shortest Path in Binary Matrix Array Breadth-First Search Matrix
Medium 55
0.5% 29 Restore IP Addresses String Backtracking
Medium 55
0.6% 30 Evaluate Division Array String Depth-First Search Breadth-First Search Union-Find Graph Theory Shortest Path
Medium 55
0.6% 31 Flatten Nested List Iterator Stack Tree Depth-First Search Design Queue Iterator
Medium 55
0.7% 32 Find Peak Element Array Binary Search
Medium 55
0.5% 33 Word Search Array String Backtracking Depth-First Search Matrix
Medium 55
0.5% 34 Meeting Rooms II Array Two Pointers Greedy Sorting Heap (Priority Queue) Prefix Sum
Medium 55
0.5%