My solutions to HackerRank problems

• 10 Days of Statistics
• 30 Days of Code
• Python
• Algorithms
• Cracking the Coding Interview
• Data Structures
• General Programming
• Implementation
• Java
• SQL

Solutions are coded using Python3, Go

10 Days of Statistics

Day	Challenge	Points	Solution
0	Mean, Median, and Mode	30
0	Weighted Mean	30
1	Quartiles	30
1	Interquartile Range	30
1	Standard Deviation	30
2	Basic Probability	10
2	More Dice	10
2	Compound Event Probability	10
3	Conditional Probability	10
3	Cards of the Same Suit	10
3	Drawing Marbles	10
4	Binomial Distribution I	30
4	Binomial Distribution II	30
4	Geometric Distribution I	30
4	Geometric Distribution II	30
5	Poisson Distribution I	30
5	Poisson Distribution II	30
5	Normal Distribution I	30
5	Normal Distribution II	30
6	The Central Limit Theorem I	30
6	The Central Limit Theorem II	30
6	The Central Limit Theorem III	30
7	Pearson Correlation Coefficient I	30
7	Spearman's Rank Correlation Coefficient	30
8	Least Square Regression Line	30
8	Pearson Correlation Coefficient II	30
9	Multiple Linear Regression	30

30 Days of Code

Day	Challenge	Points	Solution
0	Hello, World	30	main.go
1	Data Types	30	main.go
2	Operators	30	main.go
3	Intro to Conditional Statements	30	main.go
4	Class vs. Instance	30	main.go
5	Loops	30	main.go
6	Let's Review	30	main.go
7	Arrays	30	main.go
8	Dictionaries and Maps	30	main.go
9	Recursion	30	main.go
10	Binary Numbers	30	main.go
11	2D Arrays	30	main.go
12	Inheritance	30	main.go
13	Abstract Classes	30	main.go
14	Scope	30	main.go
15	Linked List	30	main.go
16	Exceptions - String to Integer	30	main.go
17	More Exceptions	30	main.go
18	Queues and Stacks	30	main.go
19	Interfaces	30	main.go
20	Sorting	30	main.go
21	Generics	30	main.go
22	Binary Search Trees	30	main.go
23	BST Level-Order Traversal	30	main.go
24	More Linked Lists	30	main.go
25	Running Time and Complexity	30	main.go
26	Nested Logic	30	main.go
27	Testing	30	main.go

Python

Subdomain	Challenge	Points	Solution
Introduction	Hello, World	5	solution.py
Introduction	If-Else	10	solution.py
Introduction	Arithmetic Operators	10	solution.py
Introduction	Division	10	solution.py
Introduction	Loops	10	solution.py
Introduction	Function	10	solution.py
Introduction	Print Function	20	solution.py
Basic Data Types	Lists	10	solution.py
Basic Data Types	Tuples	10	solution.py
Basic Data Types	List Comprehensions	10	solution.py
Basic Data Types	Find the Runner-Up Score!	10	solution.py
Basic Data Types	Nested Loops	10	solution.py
Basic Data Types	Percentage	10	solution.py
Strings	sWAP cASE	10	solution.py
Strings	String Split and Join	10	solution.py
Strings	What's Your Name?	10	solution.py
Strings	Mutations	10	solution.py
Strings	Find a string	10	solution.py
Strings	String Validators	10	solution.py
Strings	Text Alignment	10	solution.py
Strings	Text Wrap	10	solution.py
Strings	Designer Door Mat	10	solution.py
Strings	String Formatting	10	solution.py
Sets	Introduction to Sets	10	solution.py
Sets	Symmetric Difference	10	solution.py
Sets	No Idea	50	solution.py
Sets	Set.add()	10	solution.py
Sets	Set .discard(), .remove() & .pop()	10	solution.py
Sets	Set .union() Operation	10	solution.py
Sets	Set .intersection() Operation	10	solution.py
Sets	Set .difference() Operation	10	solution.py
Sets	Set .symmetric_difference() Operation	10	solution.py
Sets	Set Mutations	10	solution.py
Sets	The Captain's Room	10	solution.py
Sets	Check Subset	10	solution.py
Sets	Check Strict Superset	10	solution.py

Algorithms

Subdomain	Challenge	Points	Solution
Sorting	Quicksort 1 - Partition	10
Sorting	Marc's Cakewalk	15
Sorting	Minimum Absolute Difference in an Array	15
Sorting	Luck Balance	20
Sorting	Insertion Sort - Part 1	30
Sorting	Insertion Sort - Part 2	30
Sorting	Correctness and the Loop Invariant	30
Sorting	Running Time of Algorithms	30
Sorting	Quicksort 2 - Sorting	30
Sorting	Counting Sort 1	30
Sorting	Counting Sort 2	30
Sorting	Counting Sort 3	30
Sorting	Intro to Tutorial Challenges	30
Sorting	Quicksort In-Place	35
Sorting	Running Time of Quicksort	35
Sorting	The Full Counting Sort	40
Search	Ice Cream Parlor	30
Search	Connected Cells in a Grid	50
Greedy	Grid Challenge	20
Greedy	Maximum Perimeter Triangle	20
Greedy	Beautiful Pairs	30
Graph Theory	Breadth First Search - Shortest Reach	55
Strings	Super Reduced String	10
Strings	CamelCase	15
Strings	Two Characters	15
Strings	Caesar Cipher	15
Strings	Mars Exploration	15
Strings	Weighted Uniform Strings	20
Strings	Gemstones	20
Strings	Alternating Characters	20
Strings	Beautiful Binary String	20
Strings	The Love-Letter Mystery	20
Strings	String Construction	25
Dynamic Programming	The Coin Change Problem	60
Bit Manipulation	Lonely Integer	20
Bit Manipulation	Bit Manipulation: Lonely Integer	20
Bit Manipulation	Sum vs XOR	25
Bit Manipulation	Maximizing XOR	30
Bit Manipulation	Sansa and XOR	30
Bit Manipulation	Counter game	30

Cracking the Coding Interview

Topic	Challenge	Points	Solution
Techniques / Concepts	Time Complexity: Primality	15
Techniques / Concepts	Recursion: Fibonacci Numbers	20
Techniques / Concepts	Recursion: Davis' Staircase	30
Techniques / Concepts	DP: Coin Change	30
Techniques / Concepts	Bit Manipulation: Lonely Integer	60
Data Structures	Arrays: Left Rotation	20
Data Structures	Strings: Making Anagrams	25
Data Structures	Hash Tables: Ransom Note	25
Data Structures	Linked Lists: Detect a Cycle	25
Data Structures	Stacks: Balanced Brackets	30
Data Structures	Queues: A Tale of Two Stacks	30
Data Structures	Trees: Is This a Binary Search Tree?	30
Data Structures	Heaps: Find the Running Median	50
Data Structures	Tries: Contacts	50
Algorithms	Sorting: Bubble Sort	30
Algorithms	Sorting: Comparator	35
Algorithms	Merge Sort: Counting Inversions	35
Algorithms	Binary Search: Ice Cream Parlor	45
Algorithms	DFS: Connected Cell in a Grid	45
Algorithms	BFS: Shortest Reach in a Graph	45

Data Structures

Subdomain	Challenge	Points	Solution
Arrays	Arrays - DS	10
Arrays	2D Array - DS	15
Arrays	Dynamic Array	15
Arrays	Left Rotation	20
Arrays	Sparse Arrays	25
Arrays	Algorithmic Crush	60
Stacks	Maximum Element	20
Stacks	Balanced Brackets	25
Trees	Tree: Preorder Traversal	10
Trees	Tree: Inorder Traversal	10
Trees	Tree: Postorder Traversal	10
Trees	Tree: Height of a Binary Tree	10
Trees	Tree: Level Order Traversal	20
Trees	Tree: Huffman Decoding	20
Trees	Tree: Top View	20
Trees	Binary Search Tree: Insertion	20
Trees	Binary Search Tree: Lowest Common Ancestor	30
Trees	Is This a Binary Search Tree?	30
Trees	Swap Nodes [Algo]	40
Trees	Square-Ten Tree	60
Linked List	Print the Elements of a Linked List	5
Linked List	Insert a node at the head of a linked list	5
Linked List	Insert a Node at the Tail of a Linked List	5
Linked List	Insert a node at a specific position in a linked list	5
Linked List	Delete a Node	5
Linked List	Print in Reverse	5
Linked List	Reverse a linked list	5
Linked List	Compare two linked lists	5
Linked List	Merge two sorted linked lists	5
Linked List	Get Node Value	5
Linked List	Delete duplicate-value nodes from a sorted linked list	5
Linked List	Cycle Detection	5
Linked List	Find Merge Point of Two Lists	5
Linked List	Inserting a Node Into a Sorted Doubly Linked List	5
Linked List	Reverse a doubly linked list	5
Tries	Contacts	40
Queues	Queue using Two Stacks	30
Heaps	Find the Running Median	50
Multiple Choice	Data Structures MCQ 1	5
Multiple Choice	Data Structures MCQ 2	5
Multiple Choice	Data Structures MCQ 3	5

General Programming

Subdomain	Challenge	Points	Solution
Basic Programming	Solve Me First	1
Basic Programming	Staircase	10
Basic Programming	Plus Minus	10
Basic Programming	Diagonal Difference	10
Basic Programming	A Very Big Sum	10
Basic Programming	Simple Array Sum	10
Basic Programming	Compare the Triplets	10
Basic Programming	Divisible Sum Pairs	10
Basic Programming	Kangaroo	10
Basic Programming	Drawing Book	10
Basic Programming	Birthday Cake Candles	10
Basic Programming	Bon Appetit	10
Basic Programming	Sock Merchant	10
Basic Programming	Apple and Orange	10
Basic Programming	Between Two Sets	10
Basic Programming	Mini-max Sum	10
Basic Programming	Grading Students	10
Basic Programming	Breaking the Records	10
Basic Programming	Migratory Birds	10
Basic Programming	Birthday Chocolate	10
Basic Programming	Time Conversion	15
Basic Programming	Library Fine	15
Basic Programming	Save the Prisoner!	15
Basic Programming	Jumping on the Clouds - Revisited	15
Basic Programming	Counting Valleys	15
Basic Programming	Viral Advertising	15
Basic Programming	Beautiful Days at the Movies	15
Basic Programming	Electronics Shop	15
Basic Programming	Cats and a Mouse	15
Basic Programming	The Hurdle Race	15
Basic Programming	Utopian Tree	20
Basic Programming	Circular Array Rotation	20
Basic Programming	Sherlock and Squares	20
Basic Programming	Angry Professor	20
Basic Programming	Extra Long Factorials	20
Basic Programming	Minimum Distances	20
Basic Programming	Beautiful Triplets	20
Basic Programming	Jumping on the Clouds	20
Basic Programming	Equalize the Array	20
Basic Programming	Designer PDF Viewer	20
Basic Programming	Repeated String	20
Basic Programming	Append and Delete	20
Basic Programming	Picking Numbers	20
Basic Programming	Climbing the Leaderboard	20
Basic Programming	Sequence Equation	20
Basic Programming	Find Digits	25
Basic Programming	Cut the sticks	25
Basic Programming	Taum and B'day	25
Basic Programming	Flatland Space Stations	25
Basic Programming	Fair Rations	25
Basic Programming	Manasa and Stones	30
Object-Oriented Programming	Class vs. Instance	30
Object-Oriented Programming	Inheritance	30
Object-Oriented Programming	Abstract Classes	30
RegEx	HackerRank in a String!	20

Implementation

Subdomain	Challenge	Difficulty	Solution
Brute Force	Pangrams	20
Brute Force	Strings: Making Anagrams	25
Brute Force	Making Anagrams	30
Brute Force	Modified Kaprekar Numbers	30

Java

Subdomain	Challenge	Points	Solution
Introduction	Welcome to Java!	3
Introduction	Java Stdin and Stdout I	5
Introduction	Java If-Else	10
Introduction	Java Stdin and Stdout II	10
Introduction	Java Output Formatting	10
Introduction	Java Loops I	10
Introduction	Java Loops II	10
Introduction	Java Datatypes	10
Introduction	Java End-of-file	10
Introduction	Java Static Initializer Block	10
Introduction	Java Int to String	10
Introduction	Java Date and Time	15
Introduction	Java Currency Formatter	15
Strings	Java Strings Introduction	5
Strings	Java Substring	5
Strings	Java String Compare	10
Strings	Java String Reverse	10
Strings	Java Anagrams	10
Strings	Java String Tokens	15
Strings	Pattern Syntax Checker	20
Strings	Java Regex	25
Strings	Java Regex 2 - Duplicate Words	25
Strings	Java Regex 3 - Username Checker	20
Strings	Tag Content Extractor	20
BigNumber	Java BigInteger	10
BigNumber	Java BigDecimal	20
BigNumber	Java Primality Test	20
Data Structures	Java 1D Array	5
Data Structures	Java 2D Array	10
Data Structures	Java Subarray	10
Data Structures	Java Arraylist	10
Data Structures	Java 1D Array (Part 2)	25
Data Structures	Java List	15
Data Structures	Java Map	10
Data Structures	Java Stack	20
Data Structures	Java Hashset	10
Data Structures	Java Generics	15
Data Structures	Java Comparator	10
Data Structures	Java Sort	10
Data Structures	Java Dequeue	20
Data Structures	Java BitSet	20
Data Structures	Java Priority Queue	20
Object Oriented Programming	Java Inheritance I	5
Object Oriented Programming	Java Inheritance II	10
Object Oriented Programming	Java Abstract Class	10
Object Oriented Programming	Java Interface	10
Object Oriented Programming	Java Method Overriding	10
Object Oriented Programming	Java Method Overriding 2 (Super Keyword)	10
Object Oriented Programming	Java Instanceof keyword	10
Object Oriented Programming	Java Iterator	15
Object Oriented Programming	Calculating Volume	20
Exception Handling	Java Exception Handling (Try-catch)	10
Exception Handling	Java Exception Handling	15
Advanced	Java Varargs - Simple Addition	15
Advanced	Java Reflection - Attributes	15
Advanced	Can You Access	15
Advanced	Prime Checker	25
Advanced	Java Factory Pattern	15
Advanced	Java Singleton Pattern	15
Advanced	Java Visitor Pattern	40
Advanced	Java Annotations	25
Advanced	Covariant Return Types	20
Advanced	Java Lambda Expressions	30
Advanced	Java MD5	30
Advanced	Java SHA-256	30

SQL

Subdomain	Challenge	Points	Solution
Basic Select	Revising the Select Query I	10
Basic Select	Revising the Select Query II	10
Basic Select	Select All	10
Basic Select	Select By ID	10
Basic Select	Japanese Cities' Attributes	10
Basic Select	Japanese Cities' Names	10
Basic Select	Weather Observation Station 1	15
Basic Select	Weather Observation Station 3	10
Basic Select	Weather Observation Station 4	10
Basic Select	Weather Observation Station 5	30
Basic Select	Weather Observation Station 6	10
Basic Select	Weather Observation Station 7	10
Basic Select	Weather Observation Station 8	15
Basic Select	Weather Observation Station 9	10
Basic Select	Weather Observation Station 10	10
Basic Select	Weather Observation Station 11	15
Basic Select	Weather Observation Station 12	15
Basic Select	Higher Than 75 Marks	15
Basic Select	Employee Names	10
Basic Select	Employee Salaries	10
Basic Join	Asian Population	10
Basic Join	African Cities	10
Basic Join	Average Population of Each Continent	10
Basic Join	The Report	20
Aggregation	Revising Aggregations - The Count Function	10
Aggregation	Revising Aggregations - The Sum Function	10
Aggregation	Revising Aggregations - Averages	10
Aggregation	Average Population	10
Aggregation	Japan Population	10
Aggregation	Population Density Difference	10
Aggregation	The Blunder	15
Aggregation	Top Earners	20
Aggregation	Weather Observation Station 2	15
Aggregation	Weather Observation Station 13	10
Aggregation	Weather Observation Station 14	10
Aggregation	Weather Observation Station 15	15
Aggregation	Weather Observation Station 16	10
Aggregation	Weather Observation Station 17	15
Aggregation	Weather Observation Station 18	25
Aggregation	Weather Observation Station 19	30

Inspired from: https://github.com/rshaghoulian/HackerRank_solutions