HackerRank tutorials and challenges repository. Remember, you should just use this repo as guidance when you get stuck, but should code your own solution.
Where's the fun on ctrl + C & ctrl + V anyway? ;)

Most solutions coded using Javascript (except Language Proficiency ones).
SQL solutions use MySQL.

• 30 Days of Code
• 10 Days of Statistics
• 10 Days of Javascript
• Interview Preparation Kit
• Cracking the Coding Interview

• Algorithms
• Data Structures
• Mathematics

• Artificial Intelligence
• SQL
• Databases
• Distributed Systems
• Regex
• Security

• Java
• Python
• Functional Programming