What are your preferred sources (websites, web platforms, books, etc.) of programming challenges, drills, exercises?

Question

There's nothing better to train/improve programming skills then solving programming problems on a daily basis. What's even better is to confront own solutions with these of others, hopefully better programers. Best of all is to work on solutions in groups.

Any suggestions as to your preferred sources of programming language related or general programming challenges most welcome.

Thanks!

Answer 1

i quite like codewars.com, it has the option of numerous languages to practice in. Another one is hackerrank.com

Answer 2

@tracy
thanks a lot. like them both. already started challenges @hackerrank