All problems from day 1 of and day 2 IOI '25 have been added. You may access them here.

An unofficial mirror for day 1 and day 2 of the contest have been set up.

The problem statements and data were uploaded by X_Ray and published by maxcruickshanks.

Finally, we wish to congratulate team Canada for their amazing performance at IOI!

• skittles1412 - achieving 7th place and IOI Gold,
• littlecat - IOI Silver,
• Tarek Zaki - IOI Bronze,
• Alex Lin - IOI Bronze!

You can see the results here.

All problems from this year's CCO and CIW have been added. You may access them here and here, respectively.

Unofficial mirrors for CCO day 1, CCO day 2, CIW day 1, and CIW day 2 have also been set up.

The problem data were uploaded by BalintR, the problem statements were uploaded by Kirito, and the mirrors were made by maxcruickshanks.

An unofficial scoreboard for CCO is accessible here compiled by AustinJiang.

Finally, congratulations to littlecat, skittles1412, Alex Lin, and Tarek Zaki, who will be representing Canada at the IOI!

Hi everyone!

This Thursday, we'll be hosting the end-of-school-year OTHS Coding Competition!

The contest will be unrated. For more details, check out the contest page.

Have fun!

April Fools! Your rating has been reset to zero!

If you've been paying attention to the discussion on the DMOJ Discord recently, you may have been aware that there has been some discontent with new users being able to get Grandmaster rating after participating in a single contest with a rating ceiling intended for Candidate Master / Master rated users. In response, we've been working on overhauling the rating system, with a particular focus on contests with rating ceilings. At a very high level, ratings should not exceed 400 plus the rating ceiling (naturally, this is unbounded for contests with no rating ceilings).

All users have had their ratings retroactively changed as if DMOJ had always been using this new system. Furthermore, "rating gain caps" were added to contests labelled as "Junior" contests. (More technically, they had performance_ceiling set to 2000). Finally, rating ceilings have been retroactively removed from all previous contests (as these would no longer make sense with the new ratings). Any users who were originally not rated have been manually excluded from ratings.

The changes in rating are as follows:

For further explanation, including technical details, we recommend checking out the implementation on GitHub, the original Elo-MMR paper, and this brief discussion with the Elo-MMR creator regarding how to handle contests with rating ceilings.

Finally, please reach out, either via the comments section, via email at contact -at- dmoj -dot- ca, via the issue tracker on GitHub, or via the Discord if you have any concerns, or wish to report any issues.

Hi everyone!

We're excited to present the second edition of the April Fools' Day Contest!

The contest will start on April 1st at 0:00 EST and will last one week. Participants will not have a contest window: all 10 problems will be open for the duration of the contest.

Despite the incredible problem quality, the contest will be unrated. For more details, check out the contest page.

Have fun!

Hello everyone!

The Arcadia High School Coding Club is excited to announce the second edition of the Arcadia Computing Contest! There will be questions, with two hours to solve them. The contest will start on March 19th at 18:15 EDT and will be open for a week.

The contest will be rated for users with a rating under 1900. For more details, check out the contest page.

Good luck and we hope you enjoy the problems!

Greetings all!

I am pleased to announce my first (rated) DMOJ contest!

The contest will begin on February 18th, 2025 00:00 ET and will last one week. Participants will have a 3-hour window to solve 6 problems.

The contest is rated for all participants.

For more information, please visit the contest page.

Good luck, and have fun!

Hi everyone!

This Thursday, we'll be hosting the third OTHS Coding Competition! The format of this contest will be the same as the CCC.

The contest will be unrated. For more details, check out the contest page.

Have fun!