Hackerrank OJ

For details of explanation of solution, check this website: http://yular.github.io .

Warm Up

• Solve Me First: Problem; Code.
• Simple Array Sum: Problem; Code.
• A Very Big Sum: Problem; Code.
• Diagonal Difference: Problem; Code.
• Plus Minus: Problem; Code.
• Save The Prisoner: Problem; Code.
• Birthday Cake Candles: Problem; Code.
• Maximum Perimeter Triangle: Problem; Code.
• Staircase: Problem; Code.
• Time Conversion: Problem; Code.
• Make it Anagram: Problem; Code.
• Divisible Pairs Sum: Problem; Code.
• Nested Logic: Problem; Code.

Implementation

• Grading Students: Problem; Code.
• Angry Professor: Problem; Code.
• Beautiful Days at the Movies: Problem; Code.
• Sherlock and The Beast: Problem; Code.
• The Bomberman Game: Problem; Code.
• Climbing the Leaderboard: Problem; Code.
• Migratory Birds: Problem; Code.
• Counting Valleys: Problem; Code.
• Electronic Shop: Problem; Code.
• Magic Square Forming: Problem; Code.
• The Hurdle Race: Problem; Code.
• Organizing Containers of Balls: Problem; Code.
• Cats and a Mouse: Problem; Code.
• Drawing Book: Problem; Code.
• Design PDF Viewer: Problem; Code.
• Append and Delete: Problem; Code.
• Picking Numbers: Problem; Code.
• Permutation Equation: Problem; Code.
• Utopian Tree: Problem; Code.
• Breaking Best and Worst Record: Problem; Code.
• Happy Ladybug: Problem; Code.
• Mini Max Sum: Problem; Code.
• Compare the triplets: Problem; Code.
• Between Two Sets: Problem; Code.
• Fair Rations: Problem; Code.
• Jumping on the Clouds, Revisited: Problem; Code.
• Repeated String: Problem; Code.
• Sock Merchant: Problem; Code.
• Strange Code: Problem; Code.
• Flatland Space Stations: Problem; Code.
• Beautiful Triplets: Problem; Code.
• Jumping on the Clouds: Problem; Code.
• Absolute Permutation: Problem; Code.
• Find Digits: Problem; Code.
• Apple and Orange: Problem; Code.
• Sherlock and Squares: Problem; Code.
• Service Lane: Problem; Code.
• Strange Advertising: Problem; Code.
• Kangaroo: Problem; Code.
• Minimum Distance: Problem; Code.
• Non Divisible Subset: Problem; Code.
• Equal Stacks: Problem; Code.
• Cut the sticks: Problem; Code.
• The Grid Search: Problem; Code.
• Chocolate Feast: Problem; Code.
• Cavity Map: Problem; Code.
• Caesar Cipher: Problem; Code.
• Strings: Making Anagrams: Problem; Code.
• Library Fine: Problem; Code.
• Manasa and Stones: Problem; Code.
• ACM ICPC Team: Problem; Code.
• Bon Appétit: Problem; Code.
• Extra Long Factorials: Problem; Code.
• Taum and B'day: Problem; Code.
• The Time in Words: Problem; Code.
• Modified Kaprekar Numbers: Problem; Code.
• Encryption: Problem; Code.
• Matrix Rotation: Problem; Code.
• Lisa's Workbook: Problem; Code.
• Larry's Array: Problem; Code.
• New Year Chaos: Problem; Code.
• Equality in a Array: Problem; Code.
• Divisible Sum Pairs: Problem; Code.

Constructive Algorithm

• Array Construction: Problem; Code.
• Gaming Array: Problem; Code.
• Beautiful 3 Set: Problem; Code.

Strings

• Super Reduced String: Problem; Code.
• Mars Exploration: Problem; Code.
• Hackerrank in a String: Problem; Code.
• Separate the Numbers: Problem; Code.
• : Problem; Code.
• Beautiful Binary String: Problem; Code.
• Richie Rich: Problem; Code.
• Weighted Uniform String:Problem; Code.
• Sherlock and Valid String: Problem; Code.
• CamelCase: Problem; Code.
• String Construction: Problem; Code.
• Two Characters: Problem; Code.
• String Similarity: Problem; Code.
• Bear and Steady Gene: Problem; Code.

Sorting

• Intro to Tutorial Challenges: Problem; Code.
• Insertion Sort - Part 1: Problem; Code.
• Insertion Sort - Part 2: Problem; Code.
• Correctness and the Loop Invariant: Problem; Code.
• Running Time of Algorithms: Problem; Code.
• Quicksort 1 - Partition: Problem; Code.
• Merge Sort: Counting Inversions: Problem; Code.
• Quicksort 2 - Sorting: Problem; Code.
• Quicksort In-Place: Problem; Code.
• Fraudulent Activity Notification: Problem; Code.
• Bigger is Greater: Problem; Code.
• Running Time of Quicksort: Problem; Code.
• Counting Sort 1: Problem; Code.
• Counting Sort 2: Problem; Code.
• Counting Sort 3: Problem; Code.
• The Full Counting Sort: Problem; Code.
• Closest Numbers: Problem; Code.
• Find the Median: Problem; Code.
• Sherlock and Watson: Problem; Code.
• Almost Sorted: Problem; Code.
• Sherlock and Pairs: Problem; Code.
• Insertion Sort Advanced Analysis: Problem; Code.

Search

• Sherlock and Array: Problem; Code.
• Ice Cream Parlor: Problem; Code.
• Maximise Sum: Problem; Code.
• Minimum Loss: Problem; Code.
• DFS: Connected Cells in a Grid: Problem; Code.
• Binary Search: Ice Cream Parlor: Problem; Code.
• Hackerland Radio Transmitters: Problem; Code.
• Missing Numbers: Problem; Code.
• knightL on Chessboard: Problem; Code.
• Connected Cell in a Grid: Problem; Code.
• Count Luck: Problem; Code.
• Cut the tree: Problem; Code.
• Gridland Metro: Problem; Code.
• Pairs: Problem; Code.
• Similar Pair: Problem; Code.
• Bike Racers: Problem; Code.
• Task Scheduling: Problem; Code.
• Playing with numbers: Problem; Code.

Graph Theory

• Minimum Penalty Path: Problem; Code.
• Roads in HackerLand: Problem; Code.
• Roads and Libraries: Problem; Code.
• Demanding Money: Problem; Code.

Greedy

• Minimum Absolute Difference in An Array: Problem; Code.
• Beautiful Pairs: Problem; Code.
• Marcs Cakewalk: Problem; Code.
• Luck Balance: Problem; Code.
• Flipping Matrix: Problem; Code.
• Grid Challenge: Problem; Code.
• Goodland Electricity: Problem; Code.

Dynamic Programming

• Mandragora: Problem; Code.
• Nikita and the Game: Problem; Code.
• Consecutive 1's in Binary Numbers: Problem; Code.
• Lonely Integer - Fill the key-line!: Problem; Code; Code.
• Hexagonal Grid: Problem; Code.
• Dorsey Thief: Problem; Code.
• HackerRank City: Problem; Code.
• Abbreviation: Problem; Code.
• LCS Returns: Problem; Code.

Bit Manipulation

• XOR Strings: Problem; Code.
• What's Next: Problem; Code.
• Bitwise AND: Problem; Code.
• Lonely Integer: Problem; Code.
• Xor-sequence: Problem; Code.
• Bit Manipulation: Lonely Integer: Problem; Code.
• Sum vs XOR: Problem; Code.
• Yet Another MiniMax Problem: Problem; Code.
• A or B: Problem; Code.

Recursion

• Recursive Digit Sum: Problem; Code.
• Crossword Puzzle: Problem; Code.
• Stone Division 2: Problem; Code.
• K Factorization: Problem; Code.
• Arithmetic Expressions: Problem; Code.
• Password Craker: Problem; Code.

Game Theory

• Game of Stones: Problem; Code.
• Tower Breakers: Problem; Code.
• Fun Game: Problem; Code.
• Stone Division: Problem; Code.
• Alice and Bob's Silly Game: Problem; Code.
• A Chessboard Game: Problem; Code.
• Chessboard Game, Again!: Problem; Code.
• Introduction to Nim Game: Problem; Code.
• Misere Nim: Problem; Code.
• Nimble Game: Problem; Code.
• Bob and Ben: Problem; Code.
• Poker Nim: Problem; Code.
• Tower Breakers, Again: Problem; Code.
• Kitty and Katty: Problem; Code.

NP Complete

• Walking the Approximate Longest Path: Problem; Code.

Code Golf

Multiple Choice

Recursion

• The Power Sum: Problem; Code.
• Repeat k Sums:Problem; Code.

NP Complete

• Walking the Approximate Longest Path: Problem; Code.

Math

• Points on a Line: Problem; Code.
• Smart Number: Problem; Code.
• Best Divisor: Problem; Code.
• The Chosen One: Problem; Code.
• Wet Shark and 42: Problem; Code.
• Most Distant: Problem; Code.
• Army Game: Problem; Code.
• Leonardo and Prime: Problem; Code.

Data Structure

• Arrays- DS: Problem; Code.
• 2D Array - DS: Problem; Code.
• Print the elements of a linked list: Problem; Code.
• Array Left Rotation: Problem; Code.
• Insert a Node at the Tail of a Linked List: Problem; Code.
• Insert a node at the head of a linked list: Problem; Code.
• Insert a node at a specific position in a linked list: Problem; Code.
• Delete a Node: Problem; Code.
• Print in Reverse: Problem; Code.
• Game of Two Stacks: Problem; Code.
• Reverse a Linked List: Problem; Code.
• Compare two linked lists: Problem; Code.
• Merge two sorted linked lists: Problem; Code.
• Get Node Value: Problem; Code.
• Delete duplicate-value nodes from a sorted linked list: Problem; Code.
• Detect Cycle: Problem; Code.
• Find Merge Point of Two Lists: Problem; Code.
• Insert a node into a sorted doubly linked list: Problem; Code.
• Reverse a doubly linked list: Problem; Code.
• Tree: Preorder Traversal: Problem; Code.
• Tree: Postorder Traversal: Problem; Code.
• Tree: Inorder Traversal: Problem; Code.
• Tree: Height of a binary tree: Problem; Code.
• Tree : Top View: Problem; Code.
• Tree: Level Order Traversal: Problem; Code.
• Binary Search Tree : Insertion: Problem; Code.
• Tree: Huffman Decoding: Problem; Code.
• Binary Search Tree : Lowest Common Ancestor: Problem; Code.
• Swap Nodes [Algo]: Problem; Code.
• Poisonous Plants: Problem; Code.
• Self Balancing Tree: Problem; Code.
• Median Updates: Problem; Code.
• Maximum Element: Problem; Code.
• Balanced Parentheses: Problem; Code.
• Largest Rectangle: Problem; Code.
• QHEAP1: Problem; Code.
• Simple Text Editor: Problem; Code.
• Down To Zero II: Problem; Code.
• Jesse and Cookies: Problem; Code.
• Waiter: Problem; Code.
• Castle on the Grid: Problem; Code.
• Truck Tour: Problem; Code.
• Find Median: Problem; Code.
• Minimum Average Waiting Time: Problem; Code.
• Contact: Problem; Code.
• Sparse Array: Problem; Code.
• Castle on the Grid: Problem; Code.
• Queries with Fixed Length: Problem; Code.
• Merging communities: Problem; Code.
• Components in a graph: Problem; Code.
• No Prefix Set: Problem; Code.
• Dynamic Array: Problem; Code.
• Sparse Array: Problem; Code.
• Cube Summation: Problem; Code.
• Is This a Binary Search Tree: Problem; Code.
• Queue using Two Stacks: Problem; Code.
• AND xor OR: Problem; Code.

Design

• Abstract Classes: Problem; Code.
• Inheritance: Problem; Code.
• Class vs Instance: Problem; Code.