Coding Exercises

Here are some HackerRank problems and my solutions.

Feel free to ask any questions or make suggestions!

HackerRank assigns their problems a difficulty rating (Easy, Medium, Hard, Expert, Advanced). The assigned difficulty rating does not necessarily match how difficult programming the solution is. Some of the "medium" problems take 15 minutes to solve, and others take over an hour understanding their related problem space (such as the longest common subsequence problem).

HackerRank (71 Problems)

Warm-up Challenges

• Sales by Match (Easy) Problem | Solution

• Counting Valleys (Easy) Problem | Solution

• Jumping on the Clouds (Easy) Problem | Solution

• Repeated String (Easy) Problem | Solution

• A Very Big Sum (Easy) Problem | Solution

Arrays

• 2D Array - DS (Easy) Problem | Solution

• Arrays: Left Rotation (Easy) Problem | Solution

• New Year Chaos (Medium) Problem | Solution

• Minimum Swaps 2 (Medium) Problem | Solution

• Array Manipulation (Hard) Problem | Solution

Dictionaries and Hashmaps

• Hash Tables: Ransom Note (Easy) Problem | Solution

• Two Strings (Easy) Problem | Solution

• Sherlock and Anagrams (Medium) Problem | Solution

• Count Triplets (Medium) Problem | Solution

• Frequency Queries (Medium) Problem | Solution

Sorting

• Sorting: Bubble Sort (Easy) Problem | Solution

• Mark and Toys (Easy) Problem | Solution

• Sorting: Comparator (Medium) Problem | Solution

• Fraudulent Activity Notifications (Medium) Problem | Solution

• Merge Sort: Counting Inversions (Hard) Problem | Solution

Greedy Algorithms

• Minimum Absolute Difference in an Array (Easy) Problem | Solution

• Luck Balance (Easy) Problem | Solution

• Greedy Florist (Medium) Problem | Solution

• Max Min (Medium) Problem | Solution

• Reverse Shuffle Merge (Advanced) Problem | Solution

String Manipulation

• Strings: Making Anagrams (Easy) Problem | Solution

• Alternating Characters (Easy) Problem | Solution

• Sherlock and the Valid String (Medium) Problem | Solution

• Special String Again (Medium) Problem | Solution

• Common Child (Medium) Problem | Solution

Search

• Hash Tables: Ice Cream Parlor (Medium) Problem | Solution

• Swap Nodes [Algo] (Medium) Problem | Solution

• Pairs (Medium) Problem | Solution

• Triple Sum (Medium) Problem | Solution

• Minimum Time Required (Medium) Problem | Solution

• Maximum Subarray Sum (Hard) Problem | Solution

• Making Candies (Hard) Problem | Solution

Dynamic Programming

• Max Array Sum (Medium) Problem | Solution

• Abbreviation (Medium) Problem | Solution

• Candies (Medium) Problem | Solution

• Decibinary Numbers (Hard) Problem | Solution

Stacks and Queues

• Balanced Brackets (Medium) Problem | Solution

• Queues: A Tale of Two Stacks (Medium) Problem | Solution

• Largest Rectangle (Medium) Problem | Solution

• Min Max Riddle (Medium) Problem | Solution

• Castle on the Grid (Medium) Problem | Solution

• Poisonous Plants (Hard) Problem | Solution

Graphs

• Roads and Libraries (Medium) Problem | Solution

• Find the Nearest Clone (Medium) Problem | Solution

• BFS: Shortest Reach in a Graph (Hard) Problem | Solution

• DFS: Connected Cell in a Grid (Hard) Problem | Solution

• Matrix (Hard) Problem | Solution

Trees

• Tree: Height of a Binary Tree (Easy) Problem | Solution

• Binary Search Tree: Lowest Common Ancestor (Easy) Problem | Solution

• Trees: Is This a Binary Search Tree? (Medium) Problem | Solution

• Tree: Huffman Decoding (Medium) Problem | Solution

• Balanced Forest (Hard) Problem | Solution

Linked Lists

• Insert a node at a specific position in a linked list (Easy) Problem | Solution

• Inserting a Node Into a Sorted Doubly Linked List (Easy) Problem | Solution

• Reverse a doubly linked list (Easy) Problem | Solution

• Find Merge Point of Two Lists (Easy) Problem | Solution

• Linked Lists: Detect a Cycle (Easy) Problem | Solution

Recursion and Backtracking

• Recursion: Fibonacci Numbers (Easy) Problem | Solution

• Recursion: Davis' Staircase (Medium) Problem | Solution

• Crossword Puzzle (Medium) Problem | Solution

• Recursive Digit Sum (Medium) Problem | Solution

Miscellaneous

• Flipping Bits (Easy) Problem | Solution

• Time Complexity: Primality (Medium) Problem | Solution

• Friend Circle Queries (Medium) Problem | Solution

• Maximum XOR (Medium) Problem | Solution

SQL

• Employee Names (Easy) Problem | Solution

LeetCode (3 Problems)

• K-diff Pairs in an Array (Medium) Problem | Solution

• Longest Substring Without Repeating Characters (Medium) Problem | Solution

• Restore IP Addresses (Medium) Problem | Solution

aykrieger (1 Problem)

• First Non-Duplicate Solution

Contributing

Feel free to create a GitHub Issue or PR.

This project uses the Google Style Guide here.