TOPICS

Below is the classification of problems based on topics, useful while cementing any particular data structure, algorithm or topic.

Akhil Singh Chauhan
Creator

Air Transport

• 3. Composing flight crews

Array

• 1. Two Sum
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 108. Convert Sorted Array to Binary Search Tree
• 1095. Find in Mountain Array
• 11. Container With Most Water
• 121. Best Time to Buy and Sell Stock
• 122. Best Time to Buy and Sell Stock II
• 123. Best Time to Buy and Sell Stock III
• 135. Candy
• 136. Single Number
• 139. Word Break
• 15. 3Sum
• 152. Maximum Product Subarray
• 1636. Sort Array by Increasing Frequency
• 169. Majority Element
• 198. House Robber
• 200. Number of Islands
• 212. Word Search II
• 215. Kth Largest Element in an Array
• 217. Contains Duplicate
• 2226. Maximum Candies Allocated to K Children
• 2294. Partition Array Such That Maximum Difference Is K
• 238. Product of Array Except Self
• 240. Search a 2D Matrix II
• 268. Missing Number
• 322. Coin Change
• 33. Search in Rotated Sorted Array
• 39. Combination Sum
• 4. Median of Two Sorted Arrays
• 407. Trapping Rain Water II
• 42. Trapping Rain Water
• 442. Find All Duplicates in an Array
• 49. Group Anagrams
• 53. Maximum Subarray
• 54. Spiral Matrix
• 56. Merge Intervals
• 704. Binary Search
• 705. Design HashSet
• 706. Design HashMap
• 73. Set Matrix Zeroes
• 739. Daily Temperatures
• 74. Search a 2D Matrix
• 746. Min Cost Climbing Stairs
• 79. Word Search
• 875. Koko Eating Bananas
• 978. Longest Turbulent Subarray

Backtracking

• 212. Word Search II
• 39. Combination Sum
• 52. N-Queens II
• 79. Word Search

Binary Search

• 1095. Find in Mountain Array
• 2226. Maximum Candies Allocated to K Children
• 240. Search a 2D Matrix II
• 268. Missing Number
• 33. Search in Rotated Sorted Array
• 374. Guess Number Higher or Lower
• 4. Median of Two Sorted Arrays
• 704. Binary Search
• 74. Search a 2D Matrix
• 875. Koko Eating Bananas

Binary Search Tree

• 108. Convert Sorted Array to Binary Search Tree
• 230. Kth Smallest Element in a BST
• 703. Kth Largest Element in a Stream
• 98. Validate Binary Search Tree

Binary Tree

• 100. Same Tree
• 101. Symmetric Tree
• 103. Binary Tree Zigzag Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 108. Convert Sorted Array to Binary Search Tree
• 114. Flatten Binary Tree to Linked List
• 226. Invert Binary Tree
• 230. Kth Smallest Element in a BST
• 297. Serialize and Deserialize Binary Tree
• 543. Diameter of Binary Tree
• 703. Kth Largest Element in a Stream
• 98. Validate Binary Search Tree

Bit Manipulation

• 136. Single Number
• 191. Number of 1 Bits
• 268. Missing Number
• 29. Divide Two Integers

Breadth-First Search

• 100. Same Tree
• 101. Symmetric Tree
• 103. Binary Tree Zigzag Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 200. Number of Islands
• 207. Course Schedule
• 226. Invert Binary Tree
• 297. Serialize and Deserialize Binary Tree
• 322. Coin Change
• 407. Trapping Rain Water II

Bucket Sort

• 451. Sort Characters By Frequency

Combinatorics

• 62. Unique Paths

Counting

• 169. Majority Element
• 451. Sort Characters By Frequency

Data Stream

• 295. Find Median from Data Stream
• 703. Kth Largest Element in a Stream

Depth-First Search

• 100. Same Tree
• 101. Symmetric Tree
• 104. Maximum Depth of Binary Tree
• 114. Flatten Binary Tree to Linked List
• 200. Number of Islands
• 207. Course Schedule
• 226. Invert Binary Tree
• 230. Kth Smallest Element in a BST
• 297. Serialize and Deserialize Binary Tree
• 543. Diameter of Binary Tree
• 79. Word Search
• 98. Validate Binary Search Tree

Design

• 146. LRU Cache
• 155. Min Stack
• 208. Implement Trie (Prefix Tree)
• 295. Find Median from Data Stream
• 297. Serialize and Deserialize Binary Tree
• 355. Design Twitter
• 703. Kth Largest Element in a Stream
• 705. Design HashSet
• 706. Design HashMap

Divide and Conquer

• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 108. Convert Sorted Array to Binary Search Tree
• 169. Majority Element
• 191. Number of 1 Bits
• 215. Kth Largest Element in an Array
• 240. Search a 2D Matrix II
• 4. Median of Two Sorted Arrays
• 53. Maximum Subarray

Doubly-Linked List

• 146. LRU Cache

Dynamic Programming

• 1143. Longest Common Subsequence
• 121. Best Time to Buy and Sell Stock
• 122. Best Time to Buy and Sell Stock II
• 123. Best Time to Buy and Sell Stock III
• 139. Word Break
• 152. Maximum Product Subarray
• 198. House Robber
• 322. Coin Change
• 42. Trapping Rain Water
• 5. Longest Palindromic Substring
• 53. Maximum Subarray
• 62. Unique Paths
• 70. Climbing Stairs
• 746. Min Cost Climbing Stairs
• 978. Longest Turbulent Subarray

Graph

• 207. Course Schedule

Greedy

• 11. Container With Most Water
• 122. Best Time to Buy and Sell Stock II
• 135. Candy
• 2294. Partition Array Such That Maximum Difference Is K

Ground Transport

• 6. Depot Location

Hash Function

• 705. Design HashSet
• 706. Design HashMap

Hash Table

• 1. Two Sum
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 139. Word Break
• 141. Linked List Cycle
• 146. LRU Cache
• 1636. Sort Array by Increasing Frequency
• 169. Majority Element
• 208. Implement Trie (Prefix Tree)
• 217. Contains Duplicate
• 242. Valid Anagram
• 268. Missing Number
• 3. Longest Substring Without Repeating Characters
• 355. Design Twitter
• 424. Longest Repeating Character Replacement
• 442. Find All Duplicates in an Array
• 451. Sort Characters By Frequency
• 49. Group Anagrams
• 705. Design HashSet
• 706. Design HashMap
• 73. Set Matrix Zeroes

Heap (Priority Queue)

• 215. Kth Largest Element in an Array
• 295. Find Median from Data Stream
• 355. Design Twitter
• 407. Trapping Rain Water II
• 451. Sort Characters By Frequency
• 703. Kth Largest Element in a Stream

Interactive

• 1095. Find in Mountain Array
• 374. Guess Number Higher or Lower

LP

• 1. Mixed Integer Programming

Linked List

• 114. Flatten Binary Tree to Linked List
• 141. Linked List Cycle
• 146. LRU Cache
• 19. Remove Nth Node From End of List
• 2. Add Two Numbers
• 206. Reverse Linked List
• 21. Merge Two Sorted Lists
• 355. Design Twitter
• 705. Design HashSet
• 706. Design HashMap
• 876. Middle of the Linked List

MIP

• 1. Mixed Integer Programming
• 3. Composing flight crews
• 4. N Queen
• 6. Depot Location

Math

• 2. Add Two Numbers
• 268. Missing Number
• 29. Divide Two Integers
• 50. Pow(x, n)
• 62. Unique Paths
• 7. Reverse Integer
• 70. Climbing Stairs

Matrix

• 200. Number of Islands
• 212. Word Search II
• 240. Search a 2D Matrix II
• 4. N Queen
• 407. Trapping Rain Water II
• 54. Spiral Matrix
• 73. Set Matrix Zeroes
• 74. Search a 2D Matrix
• 79. Word Search

Memoization

• 139. Word Break
• 70. Climbing Stairs

Monotonic Stack

• 42. Trapping Rain Water
• 739. Daily Temperatures

Optimization

• 3. Composing flight crews
• 4. N Queen
• 6. Depot Location

Prefix Sum

• 238. Product of Array Except Self

Quickselect

• 215. Kth Largest Element in an Array

Recursion

• 2. Add Two Numbers
• 206. Reverse Linked List
• 21. Merge Two Sorted Lists
• 50. Pow(x, n)

Simulation

• 54. Spiral Matrix

Sliding Window

• 3. Longest Substring Without Repeating Characters
• 424. Longest Repeating Character Replacement
• 978. Longest Turbulent Subarray

Sorting

• 15. 3Sum
• 1636. Sort Array by Increasing Frequency
• 169. Majority Element
• 215. Kth Largest Element in an Array
• 217. Contains Duplicate
• 2294. Partition Array Such That Maximum Difference Is K
• 242. Valid Anagram
• 268. Missing Number
• 295. Find Median from Data Stream
• 451. Sort Characters By Frequency
• 49. Group Anagrams
• 56. Merge Intervals

Stack

• 114. Flatten Binary Tree to Linked List
• 155. Min Stack
• 20. Valid Parentheses
• 42. Trapping Rain Water
• 739. Daily Temperatures

String

• 1143. Longest Common Subsequence
• 125. Valid Palindrome
• 139. Word Break
• 20. Valid Parentheses
• 208. Implement Trie (Prefix Tree)
• 212. Word Search II
• 242. Valid Anagram
• 297. Serialize and Deserialize Binary Tree
• 3. Longest Substring Without Repeating Characters
• 344. Reverse String
• 424. Longest Repeating Character Replacement
• 451. Sort Characters By Frequency
• 49. Group Anagrams
• 5. Longest Palindromic Substring
• 79. Word Search

Topological Sort

• 207. Course Schedule

Tree

• 100. Same Tree
• 101. Symmetric Tree
• 103. Binary Tree Zigzag Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 108. Convert Sorted Array to Binary Search Tree
• 114. Flatten Binary Tree to Linked List
• 226. Invert Binary Tree
• 230. Kth Smallest Element in a BST
• 297. Serialize and Deserialize Binary Tree
• 543. Diameter of Binary Tree
• 703. Kth Largest Element in a Stream
• 98. Validate Binary Search Tree

Trie

• 139. Word Break
• 208. Implement Trie (Prefix Tree)
• 212. Word Search II

Two Pointers

• 11. Container With Most Water
• 125. Valid Palindrome
• 141. Linked List Cycle
• 15. 3Sum
• 19. Remove Nth Node From End of List
• 295. Find Median from Data Stream
• 344. Reverse String
• 42. Trapping Rain Water
• 5. Longest Palindromic Substring
• 876. Middle of the Linked List

Union Find

• 200. Number of Islands