List of Platforms offering programming challenges

1. Codewars

   https://www.codewars.com

   Languages: Clojure, C, C++, C#, Crystal, Dart, Elixir, F#, Go, Java, JavaScript, Haskell, PHP, Python, Ruby, Rust, UNIX Shell, SQL, Swift, TypeScript, Objective-C, Lua, OCaml, Scala, Kotlin, Groovy, Solidity, Erlang, R, Nim, BrainF*ck

2. Coderbyte

   https://coderbyte.com

   Languages: JavaScript, Ruby, Python, PHP, Java, Swift, Go, C++, C#, C

3. leetcode

   https://leetcode.com

   Languages: JavaScript, Ruby

4. 4clojure

   https://www.4clojure.com/

   Languages: Clojure

5. Codin Game

   https://www.codingame.com/

   Languages: Objective C, Dart, .NET, F#, OCaml, Pascal, Java, Python, Scala, JavaScript, Swift, Ruby, Rust, C#, C++, C, Groovy, Clojure, Perl, Haskell, Go, PHP, Bash, Lua

6. Exercism.io

   http://exercism.io/

7. HackerRank

   https://www.hackerrank.com

   Languages: Ada, Bash, C, C#, C++, Clojure, CoffeeScript, Common Lisp, D, Elixir, Erlang, F#, Fortran, Go, Groovy, Haskell, Java, JavaScript, Julia, Kotlin, LOLcode, Lua, OCaml, Objective-C, Octave (MATLAB), PHP, Pascal, Perl, Python, R, Racket Scheme, Ruby, Rust, Scala, Smalltalk, Swift, TCL, VB.NET, Whitespace

8. codesignla.com

   https://codesignal.com/

   Languages: JavaScript, Python, C++, Java, Ruby, C#, F#, PHP, Perl, Go, Scala, Swift, Haskell, Visual Basic, R

Coding challenges

1. Ruby quiz

   http://rubyquiz.com/