Test your programming skills
In my spare time I like to test my programming skills using online services. I've gathered quite long list and thought I can share it with other people.
Most of listed servies offer online judging of submited code or check if calculated value is correct. Many of them allow users to compete providing statistical data about efficiency, number of solved problems and even how much CPU and RAM submited solution uses.
I hope you will find out this list useful.
Programming Praxis [https://programmingpraxis.com]
mathschallenge [http://mathschallenge.net]
Sphere Online Judge (SPOJ) [http://www.spoj.com]
Project Euler [https://projecteuler.net/]
CodeChef [https://www.codechef.com]
Codeforces [http://codeforces.com]
Coderbyte [https://coderbyte.com]
CheckiO [https://checkio.org]
Codewars [https://www.codewars.com]
HackerRank [https://www.hackerrank.com]
CodeEval [https://www.codeeval.com]
CodingBat [http://codingbat.com]
CodeAbbey [http://www.codeabbey.com]
Kattis [https://open.kattis.com]
r/DailyProgrammer [https://www.reddit.com/r/dailyprogrammer/]
Rosalind [http://rosalind.info/problems/locations/]
CodinGame [https://www.codingame.com/start]
Code & Conquer [https://www.codeandconquer.co]
The AI Games [http://theaigames.com/competitions]
Advent of Code [http://adventofcode.com]
CodeCombat [https://codecombat.com]
Edabit [https://edabit.com]
HackerEarth [https://www.hackerearth.com]
LeetCode[https://leetcode.com]
CodeFights [https://codefights.com]
Robocode [http://robocode.sourceforge.net]
Screeps [https://screeps.com]
Codecademy [https://www.codecademy.com]