One of the funnest ways to learn new languages and sharpen your coding skills is to do coding challenges and puzzles. There are even competitions arranged around solving computer programming challenges and puzzles. Also, don’t be surprised if some of the problems listed show up in job interviews. This is a common way to filter out good programmers from not-so-good programmers when interviewing.
Here’s a list of nice code challenge sites. If you have a favorite I don’t have listed, please contact me and let me know.
Code challenges and puzzles
Rosalind (bioinformatics problems)
http://rosalind.info/problems/
Project Euler
https://projecteuler.net/
Code Golf
https://codegolf.
Rosetta Code
https://rosettacode.org/wiki/
Coderbyte
https://www.coderbyte.com/
HackerRank
https://www.hackerrank.com/
CodeChef
https://www.codechef.com/
LeetCode
https://leetcode.com/
SPOJ
https://www.spoj.com/problems/
**** CodinGame ****
https://www.codingame.com/
https://www.codingame.com/
codeabbey
http://www.codeabbey.com/
r/dailyprogrammer
https://www.reddit.com/r/
Ruby Quiz
http://rubyquiz.com/
code_by_math
https://www.codebymath.com/
Codeforces
http://codeforces.com/
Timus Online Judge
http://acm.timus.ru/
L-99 (Lisp-like languages … like Clojure)
http://www.ic.unicamp.br/~
4Clojure (Clojure)
http://www.4clojure.com/
I Deserve
https://www.ideserve.co.in/
code jam
https://code.google.com/
Peking University POJ
http://poj.org/problemlist
HIT Online Judge
http://acm.hit.edu.cn/