Online judge for C++, Java, Python and JavaScript

Where every algorithm
finds its star.

Practice curated problems, run code against real test cases, and help grow a community-reviewed problem set.

Curated problems with visible examples, constraints, hints and per-problem submission history.

A scratchpad for quick experiments. Pick a language, paste input, run, and read the output.

Submit your own problems and test cases. Moderators review every contribution before it goes live.

Four languages

C++, Java, Python and JavaScript run on the same judge.

Instant verdicts

Run against visible cases, then submit for the full set.

Reviewed content

Every community problem is verified before it is listed.