ACM-ICPC Training Index (2013-2016) https://icpc.baylor.edu/ICPCID/OB8R9U47XJ6A Online Judge In Mainland China http://acm.hdu.edu.cn http://poj.org http://acm.bnu.edu.cn/ http://acm.bjtu.edu.cn http://acm.zju.edu.cn http://hihocoder.com/ http://code.bupt.edu.cn/ http://vjudge.net http://acdream.info/ http://www.lydsy.com/JudgeOnline/ Russian Online Judges http://codeforces.com http://www.spoj.com/ Others Online Judges http://neerc.ifmo.ru http://icpc.iisf.or.jp/ Open Train http://opentrain.snarknews.info/ http://topcoder.com