Programming practice problems and solutions sorted by topic. Includes problems from Cracking the Coding Interview, HackerRank, and LeetCode.

Arrays

• Move Zeros

Strings

• Making Anagrams
• Remove Duplicates
• Richie Rich
• Sherlock and Valid String
• Sherlock and Anagrams
• Substring with Concatenation of All Words
• Minimum Window Substring
• Word Ladder
• Find the Closest Palindrome
• Valid Parenthesis String
• Serialize and Deserialize Binary Tree

Hash Tables

• Ransom Note
• LRU Cache
• LFU Cache
• Group Anagrams
• Insert Delete GetRandom O(1) - Duplicates allowed

Heaps

• Smallest Range
• Design Twitter

Search

• Find Minimum in Rotated Sorted Array
• Search in Rotated Sorted Array
• Kth Largest Element in Array

Sorting

• 3Sum
• 4Sum
• Fraudulent Activity Notifications
• Lily's Homework
• Wiggle Sort II

Linked Lists and Stacks

• Detect a Cycle
• Balanced Brackets
• Sort List
• Merge K Sorted Lists
• Reverse Node in k-Group
• Remove Nth Node from End of List

Binary Trees

• Is This a BST?
• Preorder Traversal
• Inorder Traversal
• Postorder Traversal
• Level-Order Traversal
• Maximum Width of Binary Tree
• Add One Row to Tree

Tries

• Contacts
• Add and Search Word

BFS/DFS

• Connected Cell in a Grid
• Shortest Reach in a Graph
• Surrounded Regions
• Minesweeper

Recursion and Dynamic Programming

• Davis' Staircase
• Coin Change
• Generate Parentheses
• Subsets
• N-Queens
• Password Cracker
• Arithmetic Expressions
• Longest Valid Parentheses
• Dungeon Game
• Decode Ways
• Edit Distance
• Longest Palindromic Subsequence
• Distinct Subsequences
• Palindrome Partitioning

Bit Manipulation

• Lonely Integer
• Maximum Product of Word Lengths
• Total Hamming Distance

UFDS

• Journey to the Moon
• Redundant Connection

Other

• Primality