VoidHub
Challenge a friend to a 1v1 duel on Codeforces-style problems
VoidHub is a practice and duel site for competitive programmers. You can challenge a friend to a 1v1 duel or solve the same problem set against the clock, using problems from Codeforces, HackerRank, UVa Online Judge and its own originals. Ranked rooms change your rating, and Blitz mode reveals problems one after another over 30 minutes.
Free · Login needed · Browser
About VoidHub
It trains contest speed and topic-by-topic practice. It suits students preparing for ICPC-style contests, and it works with the ICPC MNU Community in Egypt.
It runs in the browser and sign-up is free. For problems taken from another judge, you submit through your linked account on that judge. It also offers virtual replays of past contests and editorials.
On Breakpoint since 25 Oct 2026.
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