Links

Tutorialspoint
W3 Schools
OverAPI
API Academy
Google Open Source
Cloud Study Jam-a-thon
Google Developers
Think With Google
Leet Code
Code Wars
Hacker Rank
Recurse
dev.to
Codecademy
Coding Game
Coders Rank
Hacker Earth
Exercism
SPOJ
Programmr
TopCoder
Code Forces
Code Chef
Code Gym
Dev Challenges