Oracle LeetCode Questions
314 questions all-time · 61 easy · 194 medium · 59 hard
| # | Problem | Difficulty | Frequency | Acceptance |
|---|---|---|---|---|
| 1 | LRU Cache Hash Table, Linked List, Design, Doubly-Linked List | Medium | 100 | 0.5% |
| 2 | Longest Substring Without Repeating Characters Hash Table, String, Sliding Window | Medium | 87 | 0.4% |
| 3 | Number of Islands Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix | Medium | 83 | 0.6% |
| 4 | Two Sum Array, Hash Table | Easy | 83 | 0.6% |
| 5 | Group Anagrams Array, Hash Table, String, Sorting | Medium | 81 | 0.7% |
| 6 | Top K Frequent Elements Array, Hash Table, Divide and Conquer, Sorting, Heap (Priority Queue), Bucket Sort, Counting, Quickselect | Medium | 77 | 0.7% |
| 7 | Sliding Window Maximum Array, Queue, Sliding Window, Heap (Priority Queue), Monotonic Queue | Hard | 76 | 0.5% |
| 8 | Merge k Sorted Lists Linked List, Divide and Conquer, Heap (Priority Queue), Merge Sort | Hard | 73 | 0.6% |
| 9 | Valid Parentheses String, Stack | Easy | 73 | 0.4% |
| 10 | Merge Intervals Array, Sorting | Medium | 70 | 0.5% |
| 11 | Longest Palindromic Substring Two Pointers, String, Dynamic Programming | Medium | 69 | 0.4% |
| 12 | Spiral Matrix Array, Matrix, Simulation | Medium | 69 | 0.6% |
| 13 | Meeting Rooms II Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum | Medium | 69 | 0.5% |
| 14 | Minimum One Bit Operations to Make Integers Zero Math, Dynamic Programming, Bit Manipulation, Recursion, Memoization | Hard | 68 | 0.8% |
| 15 | Search in Rotated Sorted Array Array, Binary Search | Medium | 66 | 0.5% |
| 16 | LFU Cache Hash Table, Linked List, Design, Doubly-Linked List | Hard | 66 | 0.5% |
| 17 | Asteroid Collision Array, Stack, Simulation | Medium | 65 | 0.5% |
| 18 | Container With Most Water Array, Two Pointers, Greedy | Medium | 63 | 0.6% |
| 19 | 3Sum Array, Two Pointers, Sorting | Medium | 63 | 0.4% |
| 20 | Reverse Linked List Linked List, Recursion | Easy | 63 | 0.8% |
| 21 | Remove All Adjacent Duplicates in String II String, Stack | Medium | 63 | 0.6% |
| 22 | Trapping Rain Water Array, Two Pointers, Dynamic Programming, Stack, Monotonic Stack | Hard | 62 | 0.7% |
| 23 | Longest Consecutive Sequence Array, Hash Table, Union-Find | Medium | 62 | 0.5% |
| 24 | Min Stack Stack, Design | Medium | 62 | 0.6% |
| 25 | Minimum Absolute Difference Array, Sorting | Easy | 62 | 0.8% |
| 26 | Roman to Integer Hash Table, Math, String | Easy | 60 | 0.7% |
| 27 | Maximum Subarray Array, Divide and Conquer, Dynamic Programming | Medium | 60 | 0.5% |
| 28 | Valid Anagram Hash Table, String, Sorting | Easy | 60 | 0.7% |
| 29 | Count Pairs Of Similar Strings Array, Hash Table, String, Bit Manipulation, Counting | Easy | 60 | 0.7% |
| 30 | Maximize Value of Function in a Ball Passing Game Array, Dynamic Programming, Bit Manipulation | Hard | 60 | 0.3% |
| 31 | Rotting Oranges Array, Breadth-First Search, Matrix | Medium | 60 | 0.6% |
| 32 | Find Valid Pair of Adjacent Digits in String Hash Table, String, Counting | Easy | 60 | 0.6% |
| 33 | Generate Parentheses String, Dynamic Programming, Backtracking | Medium | 58 | 0.8% |
| 34 | Best Time to Buy and Sell Stock Array, Dynamic Programming | Easy | 58 | 0.6% |
| 35 | Binary Tree Right Side View Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | 58 | 0.7% |
| 36 | Lowest Common Ancestor of a Binary Tree Tree, Depth-First Search, Binary Tree | Medium | 58 | 0.7% |
| 37 | Decode String String, Stack, Recursion | Medium | 58 | 0.6% |
| 38 | Count Ways To Build Good Strings Dynamic Programming | Medium | 58 | 0.6% |
| 39 | Count Ways to Group Overlapping Ranges Array, Sorting | Medium | 58 | 0.4% |
| 40 | Count Distinct Numbers on Board Array, Hash Table, Math, Simulation | Easy | 58 | 0.6% |
| 41 | Minimize Length of Array Using Operations Array, Math, Greedy, Number Theory | Medium | 58 | 0.4% |
| 42 | Count the Number of Houses at a Certain Distance I Breadth-First Search, Graph Theory, Prefix Sum | Medium | 58 | 0.6% |
| 43 | Count the Number of Houses at a Certain Distance II Graph Theory, Prefix Sum | Hard | 58 | 0.2% |
| 44 | All Ancestors of a Node in a Directed Acyclic Graph Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort | Medium | 58 | 0.6% |
| 45 | Lucky Numbers in a Matrix Array, Matrix | Easy | 58 | 0.8% |
| 46 | HTML Entity Parser Hash Table, String | Medium | 58 | 0.5% |
| 47 | Design Authentication Manager Hash Table, Linked List, Design, Doubly-Linked List | Medium | 58 | 0.6% |
| 48 | Koko Eating Bananas Array, Binary Search | Medium | 58 | 0.5% |
| 49 | Median of Two Sorted Arrays Array, Binary Search, Divide and Conquer | Hard | 56 | 0.5% |
| 50 | Longest Common Prefix Array, String, Trie | Easy | 56 | 0.5% |
| 51 | Sort Colors Array, Two Pointers, Sorting | Medium | 56 | 0.7% |
| 52 | Binary Tree Zigzag Level Order Traversal Tree, Breadth-First Search, Binary Tree | Medium | 56 | 0.6% |
| 53 | Course Schedule Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort | Medium | 56 | 0.5% |
| 54 | Find Median from Data Stream Two Pointers, Design, Sorting, Heap (Priority Queue), Data Stream | Hard | 56 | 0.5% |
| 55 | Maximum Number of Events That Can Be Attended Array, Greedy, Sorting, Heap (Priority Queue) | Medium | 56 | 0.4% |
| 56 | Word Squares II Array, String, Backtracking, Sorting, Enumeration | Medium | 56 | 0.6% |
| 57 | Zigzag Conversion String | Medium | 53 | 0.5% |
| 58 | First Missing Positive Array, Hash Table | Hard | 53 | 0.4% |
| 59 | Restore IP Addresses String, Backtracking | Medium | 53 | 0.6% |
| 60 | Kth Largest Element in an Array Array, Divide and Conquer, Sorting, Heap (Priority Queue), Quickselect | Medium | 53 | 0.7% |
| 61 | Coin Change Array, Dynamic Programming, Breadth-First Search | Medium | 53 | 0.5% |
| 62 | Delete Node in a BST Tree, Binary Search Tree, Binary Tree | Medium | 53 | 0.5% |
| 63 | Contiguous Array Array, Hash Table, Prefix Sum | Medium | 53 | 0.5% |
| 64 | Diameter of Binary Tree Tree, Depth-First Search, Binary Tree | Easy | 53 | 0.7% |
| 65 | Unique Binary Search Trees Math, Dynamic Programming, Tree, Binary Search Tree, Binary Tree | Medium | 53 | 0.6% |
| 66 | Simplify Path String, Stack | Medium | 53 | 0.5% |
| 67 | Implement Trie (Prefix Tree) Hash Table, String, Design, Trie | Medium | 53 | 0.7% |
| 68 | Binary Tree Maximum Path Sum Dynamic Programming, Tree, Depth-First Search, Binary Tree | Hard | 50 | 0.4% |
| 69 | Copy List with Random Pointer Hash Table, Linked List | Medium | 50 | 0.6% |
| 70 | Majority Element Array, Hash Table, Divide and Conquer, Sorting, Counting | Easy | 50 | 0.7% |
| 71 | Kth Smallest Element in a BST Tree, Depth-First Search, Binary Search Tree, Binary Tree | Medium | 50 | 0.8% |
| 72 | Product of Array Except Self Array, Prefix Sum | Medium | 50 | 0.7% |
| 73 | Logger Rate Limiter Hash Table, Design, Data Stream | Easy | 50 | 0.8% |
| 74 | Insert Delete GetRandom O(1) Array, Hash Table, Math, Design, Randomized | Medium | 50 | 0.6% |
| 75 | Binary Tree Level Order Traversal Tree, Breadth-First Search, Binary Tree | Medium | 50 | 0.7% |
| 76 | Task Scheduler Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting | Medium | 50 | 0.6% |
| 77 | Degree of an Array Array, Hash Table | Easy | 50 | 0.6% |
| 78 | Time Based Key-Value Store Hash Table, String, Binary Search, Design | Medium | 50 | 0.5% |
| 79 | Vertical Order Traversal of a Binary Tree Hash Table, Tree, Depth-First Search, Breadth-First Search, Sorting, Binary Tree | Hard | 50 | 0.5% |
| 80 | Word Ladder Hash Table, String, Breadth-First Search | Hard | 50 | 0.5% |
| 81 | Count the Number of Infection Sequences Array, Math, Combinatorics | Hard | 50 | 0.4% |
| 82 | Integer to Roman Hash Table, Math, String | Medium | 47 | 0.7% |
| 83 | Letter Combinations of a Phone Number Hash Table, String, Backtracking | Medium | 47 | 0.7% |
| 84 | Find First and Last Position of Element in Sorted Array Array, Binary Search | Medium | 47 | 0.5% |
| 85 | Minimum Window Substring Hash Table, String, Sliding Window | Hard | 47 | 0.5% |
| 86 | Validate Binary Search Tree Tree, Depth-First Search, Binary Search Tree, Binary Tree | Medium | 47 | 0.4% |
| 87 | Gas Station Array, Greedy | Medium | 47 | 0.5% |
| 88 | Word Break II Array, Hash Table, String, Dynamic Programming, Backtracking, Trie, Memoization | Hard | 47 | 0.6% |
| 89 | Maximal Square Array, Dynamic Programming, Matrix | Medium | 47 | 0.5% |
| 90 | Search a 2D Matrix II Array, Binary Search, Divide and Conquer, Matrix | Medium | 47 | 0.6% |
| 91 | Move Zeroes Array, Two Pointers | Easy | 47 | 0.6% |
| 92 | Longest Increasing Subsequence Array, Binary Search, Dynamic Programming | Medium | 47 | 0.6% |
| 93 | Reverse Vowels of a String Two Pointers, String | Easy | 47 | 0.6% |
| 94 | Search a 2D Matrix Array, Binary Search, Matrix | Medium | 47 | 0.5% |
| 95 | String Compression Two Pointers, String | Medium | 47 | 0.6% |
| 96 | Subarray Sum Equals K Array, Hash Table, Prefix Sum | Medium | 47 | 0.5% |
| 97 | Design In-Memory File System Hash Table, String, Design, Trie, Sorting | Hard | 47 | 0.5% |
| 98 | Maximum Profit From Trading Stocks Array, Dynamic Programming | Medium | 47 | 0.5% |
| 99 | Valid Palindrome Two Pointers, String | Easy | 47 | 0.5% |
| 100 | Palindromic Substrings Two Pointers, String, Dynamic Programming | Medium | 47 | 0.7% |
| 101 | N-Queens Array, Backtracking | Hard | 47 | 0.8% |
| 102 | Merge In Between Linked Lists Linked List | Medium | 47 | 0.8% |
| 103 | Pour Water Array, Simulation | Medium | 47 | 0.5% |
| 104 | Diagonal Traverse Array, Matrix, Simulation | Medium | 47 | 0.7% |
| 105 | Longest Mountain in Array Array, Two Pointers, Dynamic Programming, Enumeration | Medium | 47 | 0.4% |
| 106 | Add Two Numbers Linked List, Math, Recursion | Medium | 43 | 0.5% |
| 107 | Rotate Image Array, Math, Matrix | Medium | 43 | 0.8% |
| 108 | Jump Game Array, Dynamic Programming, Greedy | Medium | 43 | 0.4% |
| 109 | Set Matrix Zeroes Array, Hash Table, Matrix | Medium | 43 | 0.6% |
| 110 | Word Search Array, String, Backtracking, Depth-First Search, Matrix | Medium | 43 | 0.5% |
| 111 | Largest Number Array, String, Greedy, Sorting | Medium | 43 | 0.4% |
| 112 | Course Schedule II Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort | Medium | 43 | 0.6% |
| 113 | Palindrome Number Math | Easy | 43 | 0.6% |
| 114 | Meeting Rooms Array, Sorting | Easy | 43 | 0.6% |
| 115 | Single Element in a Sorted Array Array, Binary Search | Medium | 43 | 0.6% |
| 116 | Top K Frequent Words Array, Hash Table, String, Trie, Sorting, Heap (Priority Queue), Bucket Sort, Counting | Medium | 43 | 0.6% |
| 117 | Number of Distinct Islands Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Sorting, Matrix, Hash Function | Medium | 43 | 0.6% |
| 118 | Reorganize String Hash Table, String, Greedy, Sorting, Heap (Priority Queue), Counting | Medium | 43 | 0.6% |
| 119 | Design HashMap Array, Hash Table, Linked List, Design, Hash Function | Easy | 43 | 0.7% |
| 120 | Pairs of Songs With Total Durations Divisible by 60 Array, Hash Table, Counting | Medium | 43 | 0.5% |
| 121 | Maximum Profit in Job Scheduling Array, Binary Search, Dynamic Programming, Sorting | Hard | 43 | 0.5% |
| 122 | Search Suggestions System Array, String, Binary Search, Trie, Sorting, Heap (Priority Queue) | Medium | 43 | 0.7% |
| 123 | Max Area of Island Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix | Medium | 43 | 0.7% |
| 124 | Reverse Words in a String Two Pointers, String | Medium | 43 | 0.6% |
| 125 | Count Vowel Substrings of a String Hash Table, String | Easy | 43 | 0.7% |
| 126 | Next Permutation Array, Two Pointers | Medium | 43 | 0.5% |
| 127 | Number of Visible People in a Queue Array, Stack, Monotonic Stack | Hard | 43 | 0.7% |
| 128 | Second Highest Salary Database | Medium | 43 | 0.5% |
| 129 | Consecutive Numbers Sum Math, Enumeration | Hard | 43 | 0.4% |
| 130 | Merge Two Sorted Lists Linked List, Recursion | Easy | 39 | 0.7% |
| 131 | Remove Duplicates from Sorted Array Array, Two Pointers | Easy | 39 | 0.6% |
| 132 | Combination Sum II Array, Backtracking | Medium | 39 | 0.6% |
| 133 | Permutations Array, Backtracking | Medium | 39 | 0.8% |
| 134 | Rotate List Linked List, Two Pointers | Medium | 39 | 0.4% |
| 135 | Linked List Cycle Hash Table, Linked List, Two Pointers | Easy | 39 | 0.5% |
| 136 | Delete Node in a Linked List Linked List | Medium | 39 | 0.8% |
| 137 | Maximum Number of Non-overlapping Palindrome Substrings Two Pointers, String, Dynamic Programming, Greedy | Hard | 39 | 0.4% |
| 138 | Capacity To Ship Packages Within D Days Array, Binary Search | Medium | 39 | 0.7% |
| 139 | Kth Smallest Element in a Sorted Matrix Array, Binary Search, Sorting, Heap (Priority Queue), Matrix | Medium | 39 | 0.6% |
| 140 | Maximum Good People Based on Statements Array, Backtracking, Bit Manipulation, Enumeration | Hard | 39 | 0.5% |
| 141 | Sort an Array Array, Divide and Conquer, Sorting, Heap (Priority Queue), Merge Sort, Bucket Sort, Radix Sort, Counting Sort | Medium | 39 | 0.6% |
| 142 | Kill Process Array, Hash Table, Tree, Depth-First Search, Breadth-First Search | Medium | 39 | 0.7% |
| 143 | Find the Winner of the Circular Game Array, Math, Recursion, Queue, Simulation | Medium | 39 | 0.8% |
| 144 | House Robber Array, Dynamic Programming | Medium | 39 | 0.5% |
| 145 | Permutation in String Hash Table, Two Pointers, String, Sliding Window | Medium | 39 | 0.5% |
| 146 | Find the Smallest Divisor Given a Threshold Array, Binary Search | Medium | 39 | 0.7% |
| 147 | Subarray Product Less Than K Array, Binary Search, Sliding Window, Prefix Sum | Medium | 39 | 0.5% |
| 148 | Reverse Integer Math | Medium | 39 | 0.3% |
| 149 | Divide Two Integers Math, Bit Manipulation | Medium | 39 | 0.2% |
| 150 | Surrounded Regions Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix | Medium | 39 | 0.5% |
| 151 | Minimum Array Sum Array, Dynamic Programming | Medium | 39 | 0.3% |
| 152 | Find Leaves of Binary Tree Tree, Depth-First Search, Binary Tree | Medium | 39 | 0.8% |
| 153 | Regular Expression Matching String, Dynamic Programming, Recursion | Hard | 33 | 0.3% |
| 154 | Pow(x, n) Math, Recursion | Medium | 33 | 0.4% |
| 155 | Remove Duplicates from Sorted List Linked List | Easy | 33 | 0.6% |
| 156 | Merge Sorted Array Array, Two Pointers, Sorting | Easy | 33 | 0.6% |
| 157 | Populating Next Right Pointers in Each Node Linked List, Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | 33 | 0.7% |
| 158 | Sort List Linked List, Two Pointers, Divide and Conquer, Sorting, Merge Sort | Medium | 33 | 0.6% |
| 159 | Two Sum II - Input Array Is Sorted Array, Two Pointers, Binary Search | Medium | 33 | 0.7% |
| 160 | Isomorphic Strings Hash Table, String | Easy | 33 | 0.5% |
| 161 | Minimum Size Subarray Sum Array, Binary Search, Sliding Window, Prefix Sum | Medium | 33 | 0.5% |
| 162 | Basic Calculator Math, String, Stack, Recursion | Hard | 33 | 0.5% |
| 163 | Palindrome Linked List Linked List, Two Pointers, Stack, Recursion | Easy | 33 | 0.6% |
| 164 | Integer to English Words Math, String, Recursion | Hard | 33 | 0.4% |
| 165 | Sqrt(x) Math, Binary Search | Easy | 33 | 0.4% |
| 166 | Find K Pairs with Smallest Sums Array, Heap (Priority Queue) | Medium | 33 | 0.4% |
| 167 | First Unique Character in a String Hash Table, String, Queue, Counting | Easy | 33 | 0.7% |
| 168 | Add Strings Math, String, Simulation | Easy | 33 | 0.5% |
| 169 | Island Perimeter Array, Depth-First Search, Breadth-First Search, Matrix | Easy | 33 | 0.7% |
| 170 | Rearranging Fruits Array, Hash Table, Greedy, Sort | Hard | 33 | 0.6% |
| 171 | Count Binary Substrings Two Pointers, String | Easy | 33 | 0.7% |
| 172 | Word Break Array, Hash Table, String, Dynamic Programming, Trie, Memoization | Medium | 33 | 0.5% |
| 173 | Daily Temperatures Array, Stack, Monotonic Stack | Medium | 33 | 0.7% |
| 174 | Remove All Adjacent Duplicates In String String, Stack | Easy | 33 | 0.7% |
| 175 | Distinct Subsequences String, Dynamic Programming | Hard | 33 | 0.5% |
| 176 | Non-overlapping Intervals Array, Dynamic Programming, Greedy, Sorting | Medium | 33 | 0.6% |
| 177 | Flatten Binary Tree to Linked List Linked List, Stack, Tree, Depth-First Search, Binary Tree | Medium | 33 | 0.7% |
| 178 | Contains Duplicate Array, Hash Table, Sorting | Easy | 33 | 0.6% |
| 179 | Reformat Date String | Easy | 33 | 0.7% |
| 180 | Next Greater Element I Array, Hash Table, Stack, Monotonic Stack | Easy | 33 | 0.8% |
| 181 | Find Minimum in Rotated Sorted Array Array, Binary Search | Medium | 33 | 0.5% |
| 182 | Basic Calculator II Math, String, Stack | Medium | 33 | 0.5% |
| 183 | Longest Substring with At Most K Distinct Characters Hash Table, String, Sliding Window | Medium | 33 | 0.5% |
| 184 | Calculate Amount Paid in Taxes Array, Simulation | Easy | 33 | 0.7% |
| 185 | Convert Binary Number in a Linked List to Integer Linked List, Math | Easy | 33 | 0.8% |
| 186 | All Nodes Distance K in Binary Tree Hash Table, Tree, Depth-First Search, Breadth-First Search, Binary Tree | Medium | 33 | 0.7% |
| 187 | Triangle Array, Dynamic Programming | Medium | 33 | 0.6% |
| 188 | Minimum Remove to Make Valid Parentheses String, Stack | Medium | 33 | 0.7% |
| 189 | Minimum Cost to Make Array Equal Array, Binary Search, Greedy, Sorting, Prefix Sum | Hard | 33 | 0.5% |
| 190 | Clone Graph Hash Table, Depth-First Search, Breadth-First Search, Graph Theory | Medium | 33 | 0.7% |
| 191 | Maximum Earnings From Taxi Array, Hash Table, Binary Search, Dynamic Programming, Sorting | Medium | 33 | 0.5% |
| 192 | Keys and Rooms Depth-First Search, Breadth-First Search, Graph Theory | Medium | 33 | 0.8% |
| 193 | Rotate String String, String Matching | Easy | 33 | 0.7% |
| 194 | Candy Array, Greedy | Hard | 33 | 0.5% |
| 195 | Reverse Substrings Between Each Pair of Parentheses String, Stack | Medium | 33 | 0.7% |
| 196 | Valid Sudoku Array, Hash Table, Matrix | Medium | 33 | 0.6% |
| 197 | Climbing Stairs Math, Dynamic Programming, Memoization | Easy | 33 | 0.5% |
| 198 | Frog Jump Array, Dynamic Programming | Hard | 33 | 0.5% |
| 199 | Reverse Linked List II Linked List | Medium | 33 | 0.5% |
| 200 | Meeting Rooms III Array, Hash Table, Sorting, Heap (Priority Queue), Simulation | Hard | 33 | 0.5% |
| 201 | Decrypt String from Alphabet to Integer Mapping String | Easy | 33 | 0.8% |
| 202 | Number of Closed Islands Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix | Medium | 33 | 0.7% |
| 203 | Number of Music Playlists Math, Dynamic Programming, Combinatorics | Hard | 33 | 0.6% |
| 204 | Invalid Transactions Array, Hash Table, String, Sorting | Medium | 33 | 0.3% |
| 205 | Distance to a Cycle in Undirected Graph Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort | Hard | 33 | 0.7% |
| 206 | Open the Lock Array, Hash Table, String, Breadth-First Search | Medium | 33 | 0.6% |
| 207 | Sum Root to Leaf Numbers Tree, Depth-First Search, Binary Tree | Medium | 33 | 0.7% |
| 208 | Longest Valid Parentheses String, Dynamic Programming, Stack | Hard | 25 | 0.4% |
| 209 | Sudoku Solver Array, Hash Table, Backtracking, Matrix | Hard | 25 | 0.7% |
| 210 | Combination Sum Array, Backtracking | Medium | 25 | 0.8% |
| 211 | Jump Game II Array, Dynamic Programming, Greedy | Medium | 25 | 0.4% |
| 212 | Insert Interval Array | Medium | 25 | 0.5% |
| 213 | Text Justification Array, String, Simulation | Hard | 25 | 0.5% |
| 214 | Decode Ways String, Dynamic Programming | Medium | 25 | 0.4% |
| 215 | Path Sum II Backtracking, Tree, Depth-First Search, Binary Tree | Medium | 25 | 0.6% |
| 216 | Find Peak Element Array, Binary Search | Medium | 25 | 0.5% |
| 217 | Rotate Array Array, Math, Two Pointers | Medium | 25 | 0.5% |
| 218 | Invert Binary Tree Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | 25 | 0.8% |
| 219 | Find the Duplicate Number Array, Two Pointers, Binary Search, Bit Manipulation | Medium | 25 | 0.6% |
| 220 | Validate IP Address String | Medium | 25 | 0.3% |
| 221 | Remove Nth Node From End of List Linked List, Two Pointers | Medium | 25 | 0.5% |
| 222 | Design Circular Queue Array, Linked List, Design, Queue | Medium | 25 | 0.5% |
| 223 | Backspace String Compare Two Pointers, String, Stack, Simulation | Easy | 25 | 0.5% |
| 224 | K Closest Points to Origin Array, Math, Divide and Conquer, Geometry, Sorting, Heap (Priority Queue), Quickselect | Medium | 25 | 0.7% |
| 225 | Subarrays with K Different Integers Array, Hash Table, Sliding Window, Counting | Hard | 25 | 0.7% |
| 226 | Max Consecutive Ones III Array, Binary Search, Sliding Window, Prefix Sum | Medium | 25 | 0.7% |
| 227 | Design File System Hash Table, String, Design, Trie | Medium | 25 | 0.7% |
| 228 | Minimum Number of Steps to Make Two Strings Anagram Hash Table, String, Counting | Medium | 25 | 0.8% |
| 229 | Sort Array by Increasing Frequency Array, Hash Table, Sorting | Easy | 25 | 0.8% |
| 230 | Last Stone Weight Array, Heap (Priority Queue) | Easy | 25 | 0.7% |
| 231 | Swapping Nodes in a Linked List Linked List, Two Pointers | Medium | 25 | 0.7% |
| 232 | Max Stack Linked List, Stack, Design, Doubly-Linked List, Ordered Set | Hard | 25 | 0.5% |
| 233 | Binary Search Array, Binary Search | Easy | 25 | 0.6% |
| 234 | Remove Duplicates from Sorted List II Linked List, Two Pointers | Medium | 25 | 0.5% |
| 235 | Minimum Cost to Cut a Stick Array, Dynamic Programming, Sorting | Hard | 25 | 0.6% |
| 236 | Split Array Largest Sum Array, Binary Search, Dynamic Programming, Greedy, Prefix Sum | Hard | 25 | 0.6% |
| 237 | Trapping Rain Water II Array, Breadth-First Search, Heap (Priority Queue), Matrix | Hard | 25 | 0.6% |
| 238 | Subsets Array, Backtracking, Bit Manipulation | Medium | 25 | 0.8% |
| 239 | Fraction to Recurring Decimal Hash Table, Math, String | Medium | 25 | 0.3% |
| 240 | Count of Range Sum Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set | Hard | 25 | 0.4% |
| 241 | Edit Distance String, Dynamic Programming | Medium | 25 | 0.6% |
| 242 | Minimum Operations to Halve Array Sum Array, Greedy, Heap (Priority Queue) | Medium | 25 | 0.5% |
| 243 | Count Servers that Communicate Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix, Counting | Medium | 25 | 0.7% |
| 244 | My Calendar I Array, Binary Search, Design, Segment Tree, Ordered Set | Medium | 25 | 0.6% |
| 245 | Letter Tile Possibilities Hash Table, String, Backtracking, Counting | Medium | 25 | 0.8% |
| 246 | Maximize Greatness of an Array Array, Two Pointers, Greedy, Sorting | Medium | 25 | 0.6% |
| 247 | Linked List Cycle II Hash Table, Linked List, Two Pointers | Medium | 25 | 0.6% |
| 248 | Serialize and Deserialize Binary Tree String, Tree, Depth-First Search, Breadth-First Search, Design, Binary Tree | Hard | 25 | 0.6% |
| 249 | Maximum Candies Allocated to K Children Array, Binary Search | Medium | 25 | 0.5% |
| 250 | Can Place Flowers Array, Greedy | Easy | 25 | 0.3% |
| 251 | Find All Duplicates in an Array Array, Hash Table, Sorting | Medium | 25 | 0.8% |
| 252 | Basic Calculator III Math, String, Stack, Recursion | Hard | 25 | 0.5% |
| 253 | Cache With Time Limit | Medium | 25 | 0.8% |
| 254 | Maximum Employees to Be Invited to a Meeting Array, Dynamic Programming, Depth-First Search, Graph Theory, Topological Sort | Hard | 25 | 0.6% |
| 255 | Plates Between Candles Array, String, Binary Search, Prefix Sum | Medium | 25 | 0.5% |
| 256 | Remove Linked List Elements Linked List, Recursion | Easy | 25 | 0.5% |
| 257 | Create Maximum Number Array, Two Pointers, Stack, Greedy, Monotonic Stack | Hard | 25 | 0.4% |
| 258 | Nested List Weight Sum Depth-First Search, Breadth-First Search | Medium | 25 | 0.9% |
| 259 | Count and Say String | Medium | 25 | 0.6% |
| 260 | Remove Invalid Parentheses String, Backtracking, Breadth-First Search | Hard | 25 | 0.5% |
| 261 | Minimum Sideway Jumps Array, Dynamic Programming, Greedy | Medium | 25 | 0.5% |
| 262 | Largest Divisible Subset Array, Math, Dynamic Programming, Sorting | Medium | 25 | 0.5% |
| 263 | Word Search II Array, String, Backtracking, Trie, Matrix | Hard | 25 | 0.4% |
| 264 | Maximum Depth of Binary Tree Tree, Depth-First Search, Breadth-First Search, Binary Tree | Easy | 25 | 0.8% |
| 265 | Multiply Strings Math, String, Simulation | Medium | 25 | 0.4% |
| 266 | Sparse Matrix Multiplication Array, Hash Table, Matrix | Medium | 25 | 0.7% |
| 267 | Next Greater Element III Math, Two Pointers, String | Medium | 25 | 0.4% |
| 268 | Swap Nodes in Pairs Linked List, Recursion | Medium | 25 | 0.7% |
| 269 | Remove K Digits String, Stack, Greedy, Monotonic Stack | Medium | 25 | 0.4% |
| 270 | Minimize Maximum of Array Array, Binary Search, Dynamic Programming, Greedy, Prefix Sum | Medium | 25 | 0.5% |
| 271 | Greatest Common Divisor of Strings Math, String | Easy | 25 | 0.5% |
| 272 | 3Sum Smaller Array, Two Pointers, Binary Search, Sorting | Medium | 25 | 0.5% |
| 273 | Merge Strings Alternately Two Pointers, String | Easy | 25 | 0.8% |
| 274 | Count Number of Nice Subarrays Array, Hash Table, Math, Sliding Window, Prefix Sum | Medium | 25 | 0.8% |
| 275 | Evaluate Reverse Polish Notation Array, Math, Stack | Medium | 25 | 0.6% |
| 276 | Merge Nodes in Between Zeros Linked List, Simulation | Medium | 25 | 0.9% |
| 277 | Missing Number Array, Hash Table, Math, Binary Search, Bit Manipulation, Sorting | Easy | 25 | 0.7% |
| 278 | Encode and Decode Strings Array, String, Design | Medium | 25 | 0.5% |
| 279 | Minimum Insertion Steps to Make a String Palindrome String, Dynamic Programming | Hard | 25 | 0.7% |
| 280 | Design Add and Search Words Data Structure String, Depth-First Search, Design, Trie | Medium | 25 | 0.5% |
| 281 | Boundary of Binary Tree Tree, Depth-First Search, Binary Tree | Medium | 25 | 0.5% |
| 282 | Water and Jug Problem Math, Depth-First Search, Breadth-First Search | Medium | 25 | 0.5% |
| 283 | Minimum Cost Homecoming of a Robot in a Grid Array, Greedy | Medium | 25 | 0.5% |
| 284 | The kth Factor of n Math, Number Theory | Medium | 25 | 0.7% |
| 285 | Number of Valid Words in a Sentence String | Easy | 25 | 0.3% |
| 286 | Minimum Number of Increments on Subarrays to Form a Target Array Array, Dynamic Programming, Stack, Greedy, Monotonic Stack | Hard | 25 | 0.8% |
| 287 | Collect Coins in a Tree Array, Tree, Graph Theory, Topological Sort | Hard | 25 | 0.4% |
| 288 | Kth Missing Positive Number Array, Binary Search | Easy | 25 | 0.6% |
| 289 | Maximum Size Subarray Sum Equals k Array, Hash Table, Prefix Sum | Medium | 25 | 0.5% |
| 290 | Add Two Numbers II Linked List, Math, Stack | Medium | 25 | 0.6% |
| 291 | Find in Mountain Array Array, Binary Search, Interactive | Hard | 25 | 0.4% |
| 292 | Single Number III Array, Bit Manipulation | Medium | 25 | 0.7% |
| 293 | Largest Rectangle in Histogram Array, Stack, Monotonic Stack | Hard | 25 | 0.5% |
| 294 | Counting Bits Dynamic Programming, Bit Manipulation | Easy | 25 | 0.8% |
| 295 | Merge Operations to Turn Array Into a Palindrome Array, Two Pointers, Greedy | Medium | 25 | 0.7% |
| 296 | Minimum Edge Reversals So Every Node Is Reachable Dynamic Programming, Depth-First Search, Breadth-First Search, Graph Theory | Hard | 25 | 0.6% |
| 297 | Wildcard Matching String, Dynamic Programming, Greedy, Recursion | Hard | 25 | 0.3% |
| 298 | Least Number of Unique Integers after K Removals Array, Hash Table, Greedy, Sorting, Counting | Medium | 25 | 0.6% |
| 299 | Binary Tree Level Order Traversal II Tree, Breadth-First Search, Binary Tree | Medium | 25 | 0.7% |
| 300 | Redundant Connection Depth-First Search, Breadth-First Search, Union-Find, Graph Theory | Medium | 25 | 0.7% |
| 301 | Minimum Knight Moves Breadth-First Search | Medium | 25 | 0.4% |
| 302 | Bus Routes Array, Hash Table, Breadth-First Search | Hard | 25 | 0.5% |
| 303 | Minimum Cost Path with Edge Reversals Graph Theory, Heap (Priority Queue), Shortest Path | Medium | 25 | 0.6% |
| 304 | Avoid Flood in The City Array, Hash Table, Binary Search, Greedy, Heap (Priority Queue) | Medium | 25 | 0.4% |
| 305 | Happy Number Hash Table, Math, Two Pointers | Easy | 25 | 0.6% |
| 306 | Generate Schedule Array, Math, Greedy | Medium | 25 | 0.2% |
| 307 | Flood Fill Array, Depth-First Search, Breadth-First Search, Matrix | Easy | 25 | 0.7% |
| 308 | Percentage of Users Attended a Contest Database | Easy | 25 | 0.6% |
| 309 | Reverse Nodes in k-Group Linked List, Recursion | Hard | 25 | 0.7% |
| 310 | Design Hit Counter Array, Binary Search, Design, Queue, Data Stream | Medium | 25 | 0.7% |
| 311 | Simple Bank System Array, Hash Table, Design, Simulation | Medium | 25 | 0.7% |
| 312 | Find Minimum Diameter After Merging Two Trees Tree, Depth-First Search, Breadth-First Search, Graph Theory | Hard | 25 | 0.6% |
| 313 | Path Sum III Tree, Depth-First Search, Binary Tree | Medium | 25 | 0.5% |
| 314 | Monthly Transactions I Database | Medium | 25 | 0.6% |
How to read this list
The tabs at the top split the questions by how recently people said they were asked in interviews. "Last 30 Days" is the past month, "Last 3 Months" is the past quarter, and so on. "All Time" is every question on record for this company.
Frequency is a score from 0 to 100 for how often a question showed up in that time window. A higher number means it came up more often, so the list starts with the most common questions first. Acceptance is the share of submissions that pass on LeetCode. Click any question to open it on LeetCode.