Virtual Judge

• http://poj.org/
• http://acm.zju.edu.cn/onlinejudge/
• http://livearchive.onlinejudge.org/index.php
• http://acm.sgu.ru/
• http://acm.timus.ru/
• http://acm.hust.edu.cn/
• http://www.spoj.com/
• http://acm.hdu.edu.cn/
• http://www.lydsy.com/JudgeOnline/
• http://uva.onlinejudge.org/
• http://codeforces.com/
• http://www.codah.club/
• http://judge.u-aizu.ac.jp/
• http://lightoj.com/
• http://acm.uestc.edu.cn/
• https://ac.2333.moe/
• http://acm.fzu.edu.cn/
• http://acm.csu.edu.cn/OnlineJudge/
• http://cstest.scu.edu.cn/
• http://acdream.info/
• http://www.codechef.com/
• http://codeforces.com/gyms/
• http://openjudge.cn/
• https://open.kattis.com/
• https://hihocoder.com/
• http://acm.hit.edu.cn/hoj/
• http://acm.hrbust.edu.cn/
• http://acm.mipt.ru/judge/
• https://atcoder.jp/
• https://www.hackerrank.com/
• https://www.51nod.com/
• https://arena.topcoder.com/
• https://www.e-olymp.com/en/
• https://vjudge.net
• https://cn.vjudge.net
• https://www.facebook.com/virtualjudge/
• https://t.me/joinchat/Erw7nRGwXN3iSCoKguVW3w
• https://weibo.com/u/5340553087
• https://groups.google.com/forum/#!forum/virtual-judge
• https://twitter.com/virtualjudge