DMOPC '20 November Contest

Welcome to the second DMOJ Monthly Open Programming Competition of the 2020-2021 season!

The problem writers this time are richardzhang, Kirito, PrimeNet and zhouzixiang2004.

Please note that this contest will be full feedback.

Please note that this contest will have a different tiebreaking scheme from earlier contests. (See below for details.)

This round will be rated for all participants.

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

This contest will consist of 6 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 (00:00:00 EST of December 7th), whichever comes first.

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:

  • Ties will be broken by the sum of submission times. The last submission to each problem 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 โ€” 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++.

Clarification requests for the contest must be routed through the clarification system provided on DMOJ, and not through other channels including but not limited to Discord and Slack. Furthermore, all clarification requests will be handled the way they normally are in IOI. Note that, in particular, clarification requests must come in the form of yes/no questions.

Due to rampant issues with cheating on contests that has happened recently, any suspicious behavior during the contest window may result in your rating being impacted negatively. Such behavior includes, but is not limited to:

  • Registering for the contest with at least two accounts.
  • Participating in the contest with an account that is not your primary account.
  • During the contest window, talking about the contest in more detail than answering a yes/no question about whether one participated in the contest. This includes, but is not limited to, posting spoilers about the contest and public speculation of the contest.
  • Attempting to exploit bugs in the platform to subvert the constraints of the contest.

Punishments may include performance being unrated or, for more serious infractions, being forcibly ranked at the bottom of the scoreboard.

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.


  • 16
    ross_cleary  commented on Dec. 8, 2020, 9:44 p.m.

    Will there be editorials for the other problems?

    • 19
      richardzhang  commented on Dec. 9, 2020, 7:09 p.m.

      Yes. We're working on editorials for P1 ~ P4.

  • 36
    Wangster  commented on Dec. 7, 2020, 11:20 p.m. edited

    To the DMOJ Staff and the participants, I genuinely apologize for collaborating with someone else during the contest. To clarify, BrayBray123 is my brother, who also did the contest in the same room as I did (at the same time). During the contest, we were naturally collaborating in the intensity of the moment and did not think twice about our actions. Again, I do apologize on behalf of my and my brother's actions. In the future, we'll promise such a situation will never happen again.

    • 26
      Tzak  commented on Dec. 7, 2020, 11:34 p.m.

      Are you ๐Ÿ‘ˆ kidding ๐Ÿ‘Ž ??? What the **** are you ๐Ÿ‘ˆ talking ๐Ÿ—ฃ about ๐Ÿ˜Ž๐Ÿ’ฆ man ๐Ÿ‘ฆ ? You ๐Ÿ‘ˆ are a biggest ๐Ÿ˜ looser i ๐Ÿ‘ ever ๐Ÿ˜  seen ๐Ÿ‘€ in my life ๐Ÿ’“ ! You ๐Ÿ‘ˆ was doing PIPI in your ๐Ÿ’ฉ๐Ÿ‘ˆ๐Ÿป pampers when โฐ i ๐Ÿ‘ was beating ๐Ÿ’“ DMOJ users ๐ŸŽฎ much ๐Ÿ˜ฉ๐Ÿ˜‚๐Ÿ™€ more stronger ๐Ÿ’ช๐Ÿ’ฏ then you ๐Ÿ‘ˆ! You ๐Ÿ‘ˆ are not proffesional, because proffesionals knew ๐Ÿ‘“ how to lose ๐Ÿณ and congratulate ๐Ÿ‘๐Ÿ‘Œ๐Ÿ‘Ž opponents ๐Ÿ‘‰โœ‹, you ๐Ÿ…ฑ๐Ÿ‘ˆ๐Ÿ† are like ๐Ÿ‘๐Ÿ‘Œ๐Ÿ˜ a girl ๐Ÿ‘ง๐Ÿ˜๐Ÿ‘ crying ๐Ÿ˜ญ after ๐Ÿ‘€ i ๐Ÿ‘ฅ beat ๐Ÿคœ๐Ÿป๐Ÿ‘Š๐Ÿป you ๐Ÿ‘‰! Be brave ๐Ÿ’ช๐Ÿ˜Ž, be honest โŽ to yourself and stop โŒ๐Ÿšซ this trush talkings ๐Ÿ‘„๐Ÿ—ฃ!!! Everybody ๐Ÿ‘ฅ know ๐Ÿค” that i ๐Ÿ‘๐Ÿ‘„ am very ๐Ÿ‘Œ good ๐Ÿ‘Œโค competitive โšฐ๐Ÿคท programmer ๐ŸŽฎ๐ŸŽฝ, i ๐Ÿ‘๐Ÿšซ can win ๐Ÿ†๐Ÿ’ธ anyone ๐Ÿ™‹ in the world ๐ŸŒŽ๐ŸŒ๐ŸŒ in single โ˜ contest ๐ŸŽฎ! And "d"moj ๐Ÿ•ด๐Ÿฟ "a"dmins is nobody ๐Ÿ™…๐Ÿฝ for me, just a people ๐ŸŽฎ who are crying ๐Ÿ˜ญ every ๐Ÿ’ฏ single ๐Ÿป time โฐ when โฐ i do well ๐Ÿ˜‚, ( remember ๐Ÿค” what you ๐Ÿ‘ˆ say ๐Ÿ’ฌ about ๐Ÿ’ฆ AQT ) !!! Stop ๐Ÿ™…๐Ÿผโ›”๐Ÿšซ playing ๐ŸŽฎ with my name ๐Ÿ“›, i ๐Ÿ‘ฅ deserve ๐Ÿ‘Œ๐Ÿป to have a good ๐Ÿ‘ name ๐Ÿ“› during whole ๐Ÿ’ฆ my CP ๐ŸŒ carrier ๐Ÿ›๐Ÿ”›, I ๐Ÿ‘ am Officially ๐Ÿข inviting ๐Ÿ‡ฎ๐Ÿ‡ช you ๐Ÿ‘‰๐Ÿป๐Ÿ‘ค to Codeforces lockout โšฐ๐Ÿคท duel ๐Ÿ”ฅ with the Prize ๐Ÿ˜› fund ๐Ÿ’ธ! Both of us ๐Ÿ‡บ๐Ÿ‡ธ will invest ๐Ÿ’ฐ 5000 ๐Ÿ’ฏ๐Ÿ“†$ and winner ๐Ÿ† takes ๐Ÿ‘Š it all ๐Ÿ’ฏ!

      I ๐Ÿ‘ suggest ๐Ÿ‘€ all ๐Ÿ’ฏ other people ๐Ÿ‘ซ who's ๐Ÿ“› intrested in this situation ๐ŸŽฎ, just take ๐Ÿ’… a look ๐Ÿ‘€ at my results ๐Ÿ‘€๐Ÿ’ฏ in WAC5 โ˜‘๐Ÿ“ˆ and DMOPC '19 April ๐ŸŒ๐ŸŒฟ๐Ÿ– DM::OJ โšฐ๐Ÿคท Rated ๐ŸŒ contests ๐Ÿ†๐Ÿ’ฏ, and that should be enough ๐Ÿ’ฆ... No ๐Ÿšซ need ๐Ÿ‘‰ to listen ๐Ÿ‘‚ for every โ˜ crying ๐Ÿ˜ข babe ๐Ÿ‘ถ, Wangster is always ๐Ÿ”ฅ play ๐ŸŽฎ Fair ๐Ÿ‘’ ! And if someone ๐Ÿ‘ค will continue โฉ Officially ๐Ÿ—ฝ talk ๐Ÿ—ฃโœ… about ๐Ÿ’ฆ me like ๐Ÿ’– that, we will meet ๐Ÿค in Court ๐Ÿ›! God ๐Ÿ˜‡ bless โœจ with true ๐Ÿ’ฏ! True ๐Ÿ’ฏ will never ๐Ÿ™… die ๐Ÿ’€ ! Liers will kicked ๐Ÿ˜ โ˜  off ๐Ÿ“ด...

  • 33
    Tzak  commented on Dec. 7, 2020, 3:00 a.m.

    When I grow up, I want to be like RonldLiu.

  • 36
    piddddgy  commented on Dec. 7, 2020, 2:10 a.m. edited

    RonldLiu is so cute and smart! <3 orz orz orz

    • 7
      verybadallen  commented on Dec. 7, 2020, 2:19 a.m.

      ใ‚ขใ‚ซใ‚ฆใƒณใƒˆๅใฏๅคงไฝ“ๅŒใ˜ใงใ™ใŒใ€ใ‚ใ„ใคใฏๆฐ—ใฅใ‹ใ‚Œใšใซใ™ใ‚‹ใ“ใจใŒๅ‡บๆฅใ‚‹ใจๆ€ใฃใŸ wwwwwww


  • 58
    kevinyang  commented on Dec. 6, 2020, 11:33 p.m. edited

    Interesting Quotes from RonldLiu in DMOJ HUB from like early November
    "I'm grade 11 and I'm trying to make IOI next year"
    "I have 200IQ" (This man genuinely thinks he has 200IQ)
    "the hardest S5 are like 20 points so I just have to be able to solve 20 point questions to make IOI not very hard"
    "I'm going to solve all the S1 this week, all the S2 next week, all the S3 next next week, all the S4 next next next week, and all the S5 the week after"
    "My school average is like 80" (He's trying to apply to US btw)

    I just want to ask if you really thought that you were gonna get away with submitting on a second account with very similar names. I'm really disappointed by your thought process here. Last time I talked to you, I asked you to read about this but I think you read it upside down. So I'm going to request that you read it not upside down a second time and educate yourself because you somehow believe that everyone on DMOJ is an idiot. It's for your own good. :)

  • 40
    crackersamdjam  commented on Dec. 6, 2020, 11:27 p.m. edited

    enter image description here

    Break time is over! Stop playing games! Stop playing on your phones! Stop watching OurTube!

    • 24
      Plasmatic  commented on Dec. 6, 2020, 11:34 p.m.

      Looks like my rating is getting redistributed ๐Ÿค‘๐Ÿค‘

  • 19
    Narcariel  commented on Dec. 6, 2020, 8:13 p.m.

    RonldLiu has a Big Brain

  • 17
    Render_Main  commented on Dec. 2, 2020, 1:12 p.m.

    Ties will be broken by the sum of submission times. The last submission to each problem will be used.

    Does the "last submission" refers to the latest of all submissions to one problem (including submissions after the first AC) or the latest of all submissions before and include the first AC? If I submit a non-AC solution after AC'd in one problem, will it (possibly) affect my ranking?

    • 16
      Kirito  commented on Dec. 2, 2020, 4:36 p.m.

      Yes, it includes submissions after the first AC.

  • 34
    quentin9909  commented on Nov. 29, 2020, 8:55 p.m.

    November in December :blobglare:

    • 30
      31501357  commented on Dec. 2, 2020, 2:52 p.m.

      The dmoj admins haven't learnt the months of the year yet.

      • 13
        randomperson89  commented on Dec. 5, 2020, 5:05 a.m.

        Well... does anyone even remember what the date is during the pandemic?