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 |
