DMOPC '18 December Contest

Welcome to the fourth DMOJ Monthly Open Programming Competition of the 2018-2019 season!

The problem writers this time are AvaLovelace, Kirito and r3mark.

Please note that the contests this season will be full feedback, unlike previous DMOPCs which used the pretest/systest format.

This round will be rated for all participants who submit at least once.

Before the contest date, you may wish to check out the tips and help pages.

This contest will consist of 6 main problems, the difficulty of which may range anywhere from CCC Junior to CCO level.

Some problems offer partial marks in the form of subtasks. If you cannot solve a problem fully, we encourage you to go for these partial marks.

You will have 3 hours to complete the contest. After the contest window begins, you may begin at any time. Once you enter the contest, your personal timer will start counting down and you will be able to submit until 3 hours from when you started, or until the hard deadline (noon EST of Dec. 12th), whichever comes first.

Additionally, this contest will feature a 7-th problem (Problem 0) for students who are just getting started with programming.

After joining the contest, you proceed to the Problems tab to begin. You can also go to Users if you wish to see the rankings.

We have listed below some advice as well as contest strategies:

  • Start from the beginning. Ties will be broken by the sum of times used to solve the problems starting from the beginning of the contest. The last submission time of your highest score will be used.
  • It is not guaranteed that the problems will be in order of increasing difficulty. Reading all of the statements is recommended.
  • Remove all extra debugging code and/or input prompts from your code before submitting. The judge is very strict — most of the time, it requires your output to match exactly.
  • Do not pause program execution at the end. The judging process is automated. You should use stdin / stdout to perform input / output, respectively.
  • It is guaranteed that all the problems will be solvable with C++.

At the end of the contest, you may comment below to appeal a judging verdict. In the case of appeals, the decision(s) of DMOJ staff is final.


  • 0
    silxikys  commented on Dec. 12, 2018, 5:17 p.m.

    Any ideas how to solve P5?

    • 4
      Kirito  commented on Dec. 12, 2018, 6:29 p.m.

      The problems, along with accompanying editorials will be made publicly visible once we have finished looking for cheaters and rated the contest.

  • 32
    neal  commented on Dec. 12, 2018, 4:44 a.m.


    The "last submission time of your highest score" makes no sense. I spent the last hour of the contest trying to finish the final subtask of P6 (Resistor Chains). I wasn't able to complete it, so instead I ended up with an hour of extra penalty time on the problem.

    Please change this to "the first submission time of your highest score, if > 0 points."

    • 0
      r3mark  commented on Dec. 28, 2018, 9:27 p.m.

      I'm terribly sorry everyone, but I was hasty with my promise. Due to miscommunication, this change is currently not planned. The ongoing LKP in particular will be ranked using the old method, as noted here.

    • 11
      r3mark  commented on Dec. 12, 2018, 6:23 p.m. edit 3

      Edit: See above

      It was originally implemented like so because the older DMOJ was too slow to support the more reasonable "first submission time of highest non-zero points". This contest will be rated under the current rule, but DMOJ admins will update the scoring system by the end of the month. Thank you for your participation and feedback!

  • 1
    Deemo  commented on Dec. 7, 2018, 7:46 p.m.

    How will the participants be ranked?

    • 5
      Ninjaclasher  commented on Dec. 7, 2018, 8:41 p.m.
      1. By the sum of the points earned per problem. P1 to P6 will be out of 100 points and P0 will be out of 30 points.
      2. If two people have the same number of points, by cumulative time (sum of the times it takes to solve the problems with a score > 0 points).