Hackerrank challenges

Please do not use this repository as a solution, but as inspiration or to compare your solutions.

I tried to get the maximum score for all challenges, if this was not the case, I wrote the score, which was reached with the code in the first line of the file. Sometimes there are several variants.

List of all solved challenges

(Last Update: 24. March 2019)

30 Days of Code

• Day 0 - Hello, World [Java]
• Day 1 - Data Types [Java]
• Day 2 - Operators [Java]
• Day 3 - Intro to Conditional Statements [Java]
• Day 4 - class vs instance [Java]
• Day 5 - Loops [Java]
• Day 6 - Review Loop [Java]
• Day 7 - Arrays [Java]
• Day 8 - Dictionaries and Maps [Java]
• Day 9 - Recursion [Java]
• Day 10 - Binary Numbers [Java]
• Day 11 - 2D Arrays [Java]
• Day 12 - Inheritance [Java]
• Day 13 - Abstract Classes [Java]
• Day 14 - Scope [Java]
• Day 15 - Linked List [Java]
• Day 16 - Exceptions - String to Integer [Java]
• Day 17 - More Exceptions [Java]
• Day 18 - Queues and Stacks [Java]
• Day 19 - Interfaces [Java]
• Day 20 - Sorting [Java]
• Day 21 - Generics [Java]
• Day 22 - Binary Search Trees [Java]
• Day 23 - BST Level-Order Traversal [Java]
• Day 24 - More Linked Lists [Java]
• Day 25 - Running Time and Complexity [Java]
• Day 26 - Nested Logic [Java]
• Day 27 - Testing [Java]
• Day 28 - RegEx, Patterns, and Intro to Databases [Java]
• Day 30 - bitwise and [Java]

10 Days of Javascript

• Day 00
  • Day 00 - DataTypes [js]
  • Day 00 - Hello World! [js]
• Day 01
  • Day 01 - Arithmetic Operators [js]
  • Day 01 - Functions [js]
  • Day 01 - Let and Const [js]
• Day 02
  • Day 02 - Conditional Statements If-Else [js]
  • Day 02 - Conditional Statements Switch [js]
  • Day 02 - Loops [js]
• Day 03
  • Day 03 - Arrays [js]
  • Day 03 - Try Catch and Finally [js]
  • Day 03 - Throw [js]
• Day 04
  • Day 04 - Classes [js]
  • Day 04 - Count Objects [js]
  • Day 04 - Create a Rectangle Object [js]
• Day 05
  • Day 05 - Arrow Functions [js]
  • Day 05 - Inheritance [js]
  • Day 05 - Template Literals [js]
• Day 06
  • Day 06 - Bitwise Operators [js]
  • Day 06 - JavaScript Dates [js]
• Day 07
  • Day 07 - Regular Expressions I [js]
  • Day 07 - Regular Expressions II [js]
  • Day 07 - Regular Expressions III [js]
• Day 08
  • Day 08 - Button [js, css, html]
  • Day 08 - ButtonContainer [js, css, html]

Algorithms

• Warmup
  • A very big Sum [C#]
  • Compare the Triplets [C#]
  • Diagonal Difference [C#]
  • Plus Minus [C#]
  • Simple Array Sum [C#]
  • Solve me first [C#]
  • Staircase [C#]
  • Mini Max Sum [C#]
  • Birthday Cake Candles [C#, Java]
  • Time Conversion [C#]

C++

• Introduction
  • C Tutorial Basic Data Types [C++]
  • C Tutorial Conditional if else [C++]
  • C Tutorial for lookp [C++]
  • Input and Output [C++]
  • Say Hello, World! With c++ [C++]
  • Functions [C++]
  • Pointer [C++]
  • Array Introduction [C++]
  • Variable Sized Arrays[C++]

Databases

• Relation Algebra
  • Beasics of Sets and Relations #1 [txt]
  • Beasics of Sets and Relations #2 [txt]
  • Beasics of Sets and Relations #3 [txt]
  • Beasics of Sets and Relations #4 [txt]
  • Beasics of Sets and Relations #5 [txt]
  • Beasics of Sets and Relations #6 [txt]
  • Beasics of Sets and Relations #7 [txt]
  • Database Query Languages [txt]
  • Procedual Language [txt]
  • Relational Algebra - 3 [txt]
  • Relational Algebra - 4 [txt]
  • Relations - 1 [txt]
  • Relations - 2 [txt]

Linux Shell

• Bash
  • A Personalized Echo [sh]
  • Arithmetic Operations [sh]
  • Comparing Numbers [sh]
  • Compute the average [sh]
  • Getting started with conditionals [sh]
  • Let's Echo [sh]
  • Looping and Skipping [sh]
  • Looping with Numbers [sh]
  • More on Conditionals [sh]
  • The World of Numbers [sh]
• Text Processing
  • 'Tr' Command #1 [sh]
  • 'Tr' Command #2 [sh]
  • 'Tr' Command #3 [sh]
  • Cut #1 [sh]
  • Cut #2 [sh]
  • Cut #3 [sh]
  • Cut #4 [sh]
  • Cut #5 [sh]
  • Cut #6 [sh]
  • Cut #7 [sh]
  • Cut #8 [sh]
  • Cut #9 [sh]
  • Head of a Text File #1 [sh]
  • Head of a Text File #2 [sh]
  • Middle of a Text File [sh]
  • Paste-1 [sh]
  • Paste-2 [sh]
  • Paste-3 [sh]
  • Paste-4 [sh]
  • Sort Command #1 [sh]
  • Sort Command #2 [sh]
  • Sort Command #3 [sh]
  • Sort Command #4 [sh]
  • Sort Command #5 [sh]
  • Sort Command #6 [sh]
  • Sort Command #7 [sh]
  • Tail of a Text Tile #1 [sh]
  • Tail of a Text Tile #2 [sh]
  • Uniq Command #1 [sh]
  • Uniq Command #2 [sh]
  • Uniq Command #3 [sh]
  • Uniq Command #4 [sh]

Python

• Introduction
  • Say Hello, World with Python [py]
  • Python If-Else [py]
  • Arithmetic Operators [py]
  • Division [py]
  • Loops [py]
  • Write a function [py]

Regex

• Applications
  • Saying Hi [Java]
• Assertions
  • Negative Lookahead [py]
  • Negative Lookbehind [py]
  • Positive Lookahead [py]
  • Positive Lookbehind [py]
• Backreferences
  • Backreferences To Failed Groups [py]
  • Branch Rest Groups [php]
  • Forward References [java]
  • Matching Same Text Again & Again [py]
• Character Class
  • Excluding Specific Characters [java]
  • Matching Character Ranges [java]
  • Matching Specific Characters [py]
• Grouping and Capturing
  • Alternative Matching [py]
  • Capturing & Non-Capturing Groups [py]
  • Matching Word Boundaries [py]
• Introduction
  • Matching Anything But a Newline [py]
  • Matching Digits & Non-Digit Characters [py]
  • Matching Specific String [py]
  • Matching Start & End [py]
  • Matching Whitespace & Non-Whitespace Character [py]
  • Matching Word & Non-Word Character [py]
• Repetitions
  • Matching {x, y} Repetitions [py]
  • Matching {x} Repetitions [py]
  • Matching Ending Items [py]
  • Matching One Or More Repetitions [py]
  • Matching Zero Or More Repetitions [py]

SQL

• Advanced Select
  • Binary Tree Nodes [MySQL]
  • Occupations [MySQL]
  • The Company [MySQL]
  • The Pads [MySQL]
  • Type of Triangle [MySQL]
• Aggregations
  • Average Population [MySQL]
  • Japan Population [MySQL]
  • Population Density Difference [MySQL]
  • Revising Aggregations - Averages [MySQL]
  • Revising Aggregations - The Count Function [MySQL]
  • Revising Aggregations - The Sum Function [MySQL]
  • The Blunder [MySQL]
  • Top Earners [MySQL]
  • Weather Observation Station 2 [MySQL]
  • Weather Observation Station 10 [MySQL]
  • Weather Observation Station 13 [MySQL]
  • Weather Observation Station 14 [MySQL]
  • Weather Observation Station 15 [MySQL]
  • Weather Observation Station 16 [MySQL]
  • Weather Observation Station 17 [MySQL]
  • Weather Observation Station 18 [MySQL]
  • Weather Observation Station 19 [MySQL]
  • Weather Observation Station 20 [MySQL]
• Basic Join
  • African Citirs [MySQL]
  • Asian Population [MySQL]
  • Average Population of Each Continent [MySQL]
  • Challenges [MySQL]
  • Contest Leaderboard [MySQL]
  • Ollivander's Inventory [MySQL]
  • The Report [MySQL]
  • Top Cometitors [MySQL]
• Basic Select
  • Employee Names [MySQL]
  • Employee Salaries [MySQL]
  • Higher Than 75 Marks [MySQL]
  • Japanese Cities' Attributes [MySQL]
  • Japanese Cities' Names [MySQL]
  • Revising the Select Query I [MySQL]
  • Revising the Select Query II [MySQL]
  • Select All [MySQL]
  • Select By ID [MySQL]
  • Weather Observation Station 1 [MySQL]
  • Weather Observation Station 3 [MySQL]
  • Weather Observation Station 4 [MySQL]
  • Weather Observation Station 5 [MySQL]
  • Weather Observation Station 6 [MySQL]
  • Weather Observation Station 7 [MySQL]
  • Weather Observation Station 8 [MySQL]
  • Weather Observation Station 9 [MySQL]
  • Weather Observation Station 10 [MySQL]
  • Weather Observation Station 11 [MySQL]
  • Weather Observation Station 12 [MySQL]

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Specials

• Week of Code
  • Week 34
    • Day 1 One in a tram [C#]
    • Day 2 Maximum Gcd and Sum [C#]