Home


Welcome to the Don Mills Online Judge.

If this is your first visit, please register an account. Then, try the Hello, World! problem.



Virtual Contests are Live

posted on Aug. 19, 2016, 3:32on Aug. 19, 2016, 3:32

If you've visited the contest list recently, you've probably noticed the big blue Virtual join buttons. However, when clicking them, you'll have realized that they do nothing!

Today, we are very happy to announce the completion of a virtual contest system in DMOJ — the buttons work! We hope you'll find virtual contests a useful addition.

What are virtual contests?

If you couldn't meet the deadline for participating in a contest, or would like the experience of writing a contest that ran a long time ago, virtual contests can help.

Put simply, they allow you to write a contest under the same conditions you would have, had you written it normally. You are given the same amount of time as regular contestants were, and may solve the same problems — naturally, this works best if you've not yet seen the problems. A minor note is that if the contest used pretests, you will receive full feedback instead.

The new contest timer in action.

Each contest tracks your previous participations, and these rankings are public for all users. For example, take Alice's participation in the open DMPG '16 Gold Division.

With the 2016 contest season fast approaching, we hope you'll find virtual contests a good aid in practicing in the event that you cannot attend a live contest.

Join us on Slack (or IRC)!

On a marginally related note, we operate both a channel and #dmoj on esper.net — click on either to join.

We would love to hear your feedback, and they're a great place to meet and talk with other members of the community. In the very likely case that you run into an issue with virtual contests, please let us know in one of our channels.

New Math Engines

posted on Aug. 15, 2016, 6:59on Aug. 15, 2016, 6:59

As part of the new features and improvements we have been rolling out this summer comes an enhancement which deserves a bit of explanation: the new math engines which are now being used to render mathematical expressions.

What does this mean for me?

If you are using Firefox, you should notice much improved page load speeds, with the large MathJax JavaScript library and fallback SVGs no longer necessary. If you are using a different browser (e.g., Chrome), you will still benefit from less text shifting during page load, as the new SVG/PNG math renderer sizes images almost identically to MathJax.

To top this off, we are now shipping a rendering server enabling problem authors to use LaTeX commands directly in their problems, allowing crisp, scalable diagrams to be displayed.

We have put effort into making sure the math looks good on all browsers by default, but should you find something looks weird, read on (and please let us know).

Can I change the way math is displayed?

When editing your profile, you will see a new dropdown has been added, which allows you to configure the way math is displayed for you while logged in. There are 5 modes available:

Mode Description
Leave as LaTeX Perform no math rendering; output raw LaTeX commands.
SVG with PNG fallback Display scalable vector math, falling back to PNG if your browser does not support SVG
MathML only If you are using Firefox or another browser (not Chrome) that implements the MathML part of the HTML5 specification, math will be formatted as MathML commands with native browser support. To see if your browser renders MathML properly, you can visit this page to find out.
MathJax with SVG/PNG fallback This has been the default used on the DMOJ until now, and uses the MathJax library to format math. If JavaScript is disabled, it falls back on SVG or PNG math, depending on browser support.
Detect best quality This mode attempts to use caniuse.com data for a best-effort-guess of whether MathML is supported by your browser. It will use MathML if possible, and MathJax with SVG/PNG fallback when MathML is unsupported. This is now the default mode.

TSOC '16 #2

posted on April 15, 2016, 11:16on April 15, 2016, 11:16

Thanks to everyone who participated in this year's April 20 contest!

Congratulations to the top three contestants:

  1. d
  2. r3mark
  3. ZQFMGB12

We hope you enjoyed the contest! If you have any suggestions or wish to contact the problemsetters, you may reach them via tsscomputerclub@gmail.com.


The fabled April 20 Contest, 2016 will be open starting April 20th!

From Wednesday, April 20th to Sunday, April 24th, challenge your friends and dastardly foes in the battle royale of a lifetime – the competition of mythical proportions known only as the April 20 Contest, brought to you by your pals at Thornhill.

Contestants may participate in any 3-hour window between 1 AM EST on the 20th and 11PM EST on the 24th. Anyone with a DMOJ account is welcome to participate, so register for an account if you haven't already. Please see the contest page for more details.

Don Mills Programming Gala 2016

posted on April 15, 2016, 12:49on April 15, 2016, 12:49

As the academic year comes to an end, we'll be holding our final DMOPC in the form of the Don Mills Programming Gala, which will take place at Don Mills C.I. on Wednesday, May 18th.

The contest will be split into three divisions of increasing difficulty, with prizes awarded to the top competitors. For interested competitors unable to attend the on-site event, we will also be hosting mirrors of the divisions, open for anyone to participate in.

Space is limited, so sign up soon! More details and registration options may be found here. You can find results and photos from last year's DMPG here.

Registration is now closed.

DMOPC '15 April Contest

posted on April 2, 2016, 11:47on April 2, 2016, 11:47

Thanks to everyone who participated in this month's DMOPC!

Congratulations to the winners:

  1. Deemo (perfect score)
  2. d
  3. alei
  4. grikukan
  5. Mariya

We hope you enjoyed the contest! Stay tuned for news on DMPG - the final contest of the year which will be onsite!


On Tuesday, April 12th, we'll be hosting the April Don Mills Open Programming Contest!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Contestants may participate in any 3-hour window between 12PM EST and 12AM EST. Please see the contest page for more details.

See you soon, and good luck!

TLE '16

posted on March 15, 2016, 10:10on March 15, 2016, 10:10

Thanks to everyone who participated in TLE '16!

Congratulations to the winners:

  1. Butane
  2. r3mark
  3. jeffreyxiao
  4. arock
  5. gongy

Editorials will be available on the respective problem pages. We hope you enjoyed the contest!

DMOPC '15 March Contest

posted on Feb. 23, 2016, 4:14on Feb. 23, 2016, 4:14

Thanks to everyone who participated in this month's DMOPC!

Congratulations to the winners:

  1. d (perfect score)
  2. Butane
  3. bruce
  4. kobortor
  5. ZQFMGB12

We hope you enjoyed the contest! See you next month!


On Tuesday, March 1st, we'll be hosting the March Don Mills Open Programming Contest! Important note: this is one week before the standard date, due to the CCOQR taking place on March 8th.

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Contestants may participate in any 3-hour window between 12PM EST and 9PM EST. Please see the contest page for more details.

See you soon, and good luck!

CCC 2016 Problems

posted on Feb. 20, 2016, 1:40on Feb. 20, 2016, 1:40

We have added all CCC 2016 problems to the Don Mills Online Judge.

You may find them here: http://www.dmoj.ca/problems/?search=%22ccc+%2716%22.

DMOPC '15 February Contest

posted on Jan. 28, 2016, 12:37on Jan. 28, 2016, 12:37

Thanks to everyone who participated in this month's DMOPC!

Congratulations to the winners:

  1. alei
  2. ZQFMGB12
  3. d
  4. Butane
  5. grikukan

We hope you enjoyed the contest! All problems have been moved to the main judge, and editorials may be found on the problem pages by clicking "Read editorial". See you next month!


On Tuesday, February 9, we'll be hosting the February Don Mills Open Programming Contest!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Contestants may participate in any 3-hour window between 12PM EST and 9PM EST. Please see the contest page for more details.

See you soon, and good luck!

DMOPC '15 January Contest

posted on Jan. 11, 2016, 2:50on Jan. 11, 2016, 2:50

Thanks to everyone who participated in this month's DMOPC!

Congratulations to the winners:

  1. gendelpiekel (perfect score)
  2. jeffreyxiao (perfect score)
  3. d (perfect score)
  4. Quantris (perfect score)
  5. Butane

We hope you enjoyed the contest! Editorials can be found here. See you next month!


The contest was set by members of Cygnus Computer, a competitive programming club based in Bucharest, Romania. Cygnus has contributed to the localization of the site (you may change your language at the bottom of every page), and is now running a Romanian-language version of DMOJ at http://cygnus-computer.ro/arena/. Thanks!


On Tuesday, January 12th, we'll be hosting the January Don Mills Open Programming Contest!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

The problem writers this time are StellarCF, ionutpop118, and WallE256.

Contestants may participate in any 3-hour window between 12PM EST and 9PM EST. Please see the contest page for more details.

See you soon, and good luck!