learn algorithm
#Tutorial
https://www.coursera.org/
https://www.geeksforgeeks.org/
https://www.edx.org/learn/algorithms
https://www.freecodecamp.org/
https://www.wikipedia.org/
https://petr-mitrichev.blogspot.com/
https://www.udemy.com/
Youtube
MIT courseware for algorithms by Erik Demaine
#Practice
https://www.hackerrank.com/
https://leetcode.com/
https://www.spoj.com/
https://www.codewars.com/
https://www.codechef.com/
https://codeforces.com/
https://www.topcoder.com/
https://www.codingame.com/
https://www.coderbyte.com/
https://projecteuler.net/
https://exercism.io/