Upd. 2015-03-25: the new comment system is in place.

Upd. 2015-02-02: over 100 comments were deleted today, bringing comment count down from 672 to 551.

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Over the past few months we've had many users participate in comment threads across many problems. While we encourage a lively community, we'd also like to keep discussions focused and on-topic, which in the last few weeks has not always been the case.

A number of people have noticed the lack of an Edit option for comments. This is not a bug or oversight; it's by design. We encourage you to think about what you want to write before writing it, knowing that your comment is immutable and there to stay. In this sense, we're promoting well thought-out comments. The lack of an Edit option is not so that you can reply to your own comment with revisions or addendums! Having massive Re: Re: Re: Re: Re: Re: chains was certainly not a design goal, and we'll be taking steps to prevent these in the future.

But we can't do so without everyone's cooperation. In the future, we ask that everyone attempt to follow a set of simple guidelines when posting.

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Commenting Guidelines

Before posting, ask yourself:

• Will someone reading my comment a year from now find it useful? If not, then you probably shouldn't post it.
• Will I regret posting this comment in five minutes? If so, you shouldn't post it. Listen to yourself.
• Is my comment meaningful? Comments like "uw0tm8" are unwelcome.
• Is the thread I'm commenting on longer than the problem itself? If it is, do you really have something of value to add?

This is not to say that jokes or witty comments are unwelcome. They're fine. If you think your comment relates to the problem and is funny for the majority of people who will read it (i.e. not an inside joke only you and your friend will understand — we're not Facebook), then by all means post ahead! If you can brighten someone's day while remaining even remotely on topic, that's great.

And these are just guidelines. If you feel really justified in posting something, use your judgement.

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Comment Cleanup

At this time, many problem threads are cluttered with off-topic chatter of little value.

To resolve the issue of noise comments, we'll be retroactively applying the guidelines above to threads that we feel need it. This means that we'll be both editing and deleting comments that need attention. Over the next few days, you might have some of your comments deleted. If you feel strongly about a comment that we might delete, please do not hesitate to contact us: we store comment records, and they won't disappear if your comment does.

We'll also be rolling out revision-based comment edit system sometime _relatively soon. Being able to edit your comments does not mean you should not follow the simple guidelines listed above. We're adding it for the incidental case of typos and such, and your comment's edit history will be public.

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Thanks, your admins: Xyene, FatalEagle, and quantum.

Update: Thank you to all who participated!
If you were not able to take part (probably due to actual exams), below are the problems for you to solve post-contest:

French Homework
Physics Duel
Chemistry Homework
Exam Delay
Happy Teachers
Math Homework

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The first Don Mills Open Programming Competition of 2015 will be held on Tuesday, January 13 from 3:30 to 8:30 PM.

There were initially no plans for a January Contest due to exams, which is why Sentient came up with a contest based on exams! Therefore you may think of this as the January Contest, except that it will be 5 hours long rather than the usual 3 (the difficulty will remain similar to previous DMOPCs and it should take most participants about an hour to solve the first 3 problems).

You can access the contest page here.

Back in the days students were forced to choose between studying for their school exams and participating in programming contests. No more will they have to endure such harsh conditions! With the creation of the Exam Time Contest, you can prepare for your exams as you complete the questions in this contest.

Moreover, what was supposed to be an ordinary exam week at Don Mills takes a turn for the extraordinary in the last few problems.

Do you find yourself with nothing to do even on December 25?

Xyene and Kirito have prepared a contest for this day. The contest will last for 4 days, and there are 3 problems in total.

The theme is about trees. If you like trees or want to learn more about graph theory, you should check out this contest.

https://dmoj.ca/contest/christmastree

Unfortunately, the author of the contest has decided to push the contest back to December 29. We are sorry for the inconvenience!

In its place, we offer a new contest about trees -- check the contest page for more details!

Oh no, the Phantom has kidnapped Christine Daaé and is about to force her into a marriage with him. Raoul, the vicomte de Chagny, is anxious to stop this, and make Christine marry him instead return freedom to Christine. The Persian, an old acquaintance of the Phantom, is also determined to stop the Phantom's terrorism of the Opera house, and to save Christine from a forced marriage, joins in with Raoul.

The Phantom hid Christine inside his house on the lake under the Opera house, well guarded. Can you help the duo break through all the defences to save Christine? We know that the Phantom, like any other crypto nerd, likes prime numbers...

The pressure is on. Solve these problems!

• The Mirror
• The Third Cellar
• The Torture Chamber
• And the ultimate challenge: Phantom's Python Challenge

Contest Link: https://dmoj.ca/contest/stnbd

It is an ongoing week-long contest. Check out the contest page for more details.

Thanks to everyone who participated in the DMOPC December! The contest is now over.

If you have the time, please fill out an anonymous survey so we can make the next DMOPC even better.

If you have disagreements about judging verdicts, feel free to send them to us. We don't guarantee anything, but we will certainly read your appeal and consider it carefully.