The Don Mills Online Judge is a modern contest platform and archive of programming problems. It's also entirely open source.

We host problems from past CCC, CCO, COCI, IOI and JOI competitions, as well as various problems from other sources. We also run our own monthly Don Mills Open Programming Competition (DMOPC) for anyone interested in competitive programming.

The DMOJ was inspired by the PEG online judge.

I got some feedback from the judge that I don't understand.

Check out our page on status codes and their explanations.

I have an issue, how can I get in contact with an administrator?

Administrators of DMOJ may be reached through the email address admin at dmoj dot ca. If you have an issue, don’t hesitate to get in touch.

Can I contribute to the DMOJ?

Of course! There’s plenty to be done, from translating the site to reporting and fixing bugs, as well the most important task of all: adding more problems! (see below)

Some problems I’d like to practice on are missing!

You may contact an administrator if you’d like a contest added to the judge, or you may add them yourself – the DMOJ problem format is well documented. In either case, please contact an administrator.

Can I host a contest on the DMOJ?

Yes, and we’d love to help you get it up and running! Experienced or enthusiastic coders can contact us to host their own contest free of charge on the DMOJ.

I’d like to host a private contest, can I?

Yes, if you are an educational organization and would like to host a contest for your members, we can help you out. Just contact us!