readme.md

317 efficient solutions to HackerRank problems

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

Solutions are coded using Java 8

SQL solutions are coded using MySQL

10 Days of Statistics

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

30 Days of Code

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

Algorithms

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

Cracking the Coding Interview

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

Data Structures

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

General Programming

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

Implementation

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

Java

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

SQL

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