• 10 Days of JavaScript
• 10 Days of Statistics
• 30 Days of Code
• Algorithms
• Interview Preparation Kit
• Databases
• Data Structures
• Linux Shell
• Java
• RegEx
• Ruby
• SQL

10 Days of JavaScript

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

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

Interview Preparation Kit

Databases

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	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

Linux Shell

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
Assertions	Java 1D Array	5
Assertions	Java 2D Array	10
Assertions	Java Subarray	10
Assertions	Java Arraylist	10
Assertions	Java 1D Array (Part 2)	25
Assertions	Java List	15
Assertions	Java Map	10
Assertions	Java Stack	20
Assertions	Java Hashset	10
Assertions	Java Generics	15
Assertions	Java Comparator	10
Assertions	Java Sort	10
Assertions	Java Dequeue	20
Assertions	Java BitSet	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

RegEx

Subdomain	Challenge	Points	Solution
Introduction	Matching Specific String	5	SpecificString.rb
Introduction	Matching Anything But a Newline	5	AnythingButNewline.rb
Introduction	Matching Digits & Non-Digit Characters	5	DigitsNonDigitsChar.rb
Introduction	Matching Whitespace & Non-Whitespace Character	5	WhitespaceNonWhitespaceChar.rb
Introduction	Matching Word & Non-Word Character	5	WordNonWordChar.rb
Introduction	Matching Start & End	5	StartEnd.rb
Character Class	Matching Specific Characters	10	SpecificCharacters.php
Character Class	Excluding Specific Characters	10	ExcludingSpecificCharacters.php
Character Class	Matching Character Ranges	10	CharacterRanges.php
Repetitions	Matching {x} Repetitions	20	xRepetitions.php
Repetitions	Matching {x, y} Repetitions	20	xyRepetitions.php
Repetitions	Matching Zero Or More Repetitions	20	ZeroOrMoreRepetitions.php
Repetitions	Matching One Or More Repetitions	20	OneOrMoreRepetitions.php
Repetitions	Matching Ending Items	20	EndingItems.php
Grouping and Capturing	Matching Word Boundaries	20	WordBoundaries.php
Grouping and Capturing	Capturing & Non-Capturing Groups	20	CapturingNonCapturingWords.php
Grouping and Capturing	Alternative Matching	20	AlternativeMatching.php
Backreferences	Matching Same Text Again & Again	20	SameTextAgainAgain.php
Backreferences	Backreferences To Failed Groups	20	FailedGroups.php
Backreferences	Branch Reset Groups	20	BranchResetGroups.php
Backreferences	Forward References	20	ForwardReferences.php
Assertions	Positive Lookahead	20	PositiveLookahead.php
Assertions	Negative Lookahead	20	NegativeLookahead.php
Assertions	Positive Lookbehind	20	PositiveLookbehind.php
Assertions	Negative Lookbehind	20	NegativeLookbehind.java

Ruby

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
Basic Join	Top Competitors	30
Basic Join	Ollivander's Inventory	30
Basic Join	Challenges	30
Basic Join	Contest Leaderboard	30
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
Aggregation	Weather Observation Station 20	30
Alternative Queries	Draw The Triangle 1	25	DrawTheTriangle1.sql
Alternative Queries	Draw The Triangle 2	25	DrawTheTriangle2.sql
Alternative Queries	Print Prime Numbers	40	PrintPrimeNumbers.sql
Advanced Select	Type of Triangle	20	TypeOfTriangle.sql
Advanced Select	The PADS	30	ThePads.sql
Advanced Select	Occupations	30	Occupations.sql
Advanced Select	Binary Tree Nodes	30	BinaryTreeNodes.sql
Advanced Select	New Companies	30	NewCompanies.sql
Advanced Join	SQL Project Planning	40	SQLProjectPlanning.sql
Advanced Join	Placements	40	Placements.sql
Advanced Join	Symmetric Pairs	40	SymmetricPairs.sql
Advanced Join	Interviews	50	Interviews.sql
Advanced Join	15 Days of Learning SQL	50	15DaysOfLearning.sql