physics0523's blog

Codeforces Round #654 (Div. 2)
By physics0523, history, 4 years ago, In English

Codeforcesの皆さん、こんにちは!(Hello, Codeforces!)

I'm glad to invite you to my first contest, Codeforces Round 654 (Div. 2) which will be held on Jul/01/2020 16:35 (Moscow time) (notice earlier time than usual). All of the problems were mainly written and prepared by me. The round is rated if your rating is strictly less than 2100.

You will be given 6 problems (one problem has a subtask) and 2 hours to solve them. Please, read all the problems.

I would really like to thank:

The scoring distribution will be announced later.

Good luck, have fun and wish your high ratings :)

UPD: Scoring distribution : $$$500 - 1000 - 1250 - 1500 - (1500 + 1250) - 3000$$$

UPD: Editorial is out

  • Vote: I like it
  • +732
  • Vote: I do not like it

Comments Comments (411)
| Write comment?
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Auto comment: topic has been updated by physics0523 (previous revision, new revision, compare).

→ Reply
»
4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

Thanks for all of these frequent rounds!

→ Reply
»
4 years ago, # |
  Vote: I like it +137 Vote: I do not like it

I hate Physics. Hopefully no problem related to physics!

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +14 Vote: I do not like it

    Even though I love Physics , I still hope there will be no physics related problems. XD.

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    same here pal.XD

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +19 Vote: I do not like it

    I think Physics problems would be easier than the problems in this round

    → Reply
»
4 years ago, # |
  Vote: I like it +6 Vote: I do not like it

Good luck on your maiden round!

→ Reply
»
4 years ago, # |
  Vote: I like it +61 Vote: I do not like it

As a tester, I can say that the problems are really interesting and hopefully you will enjoy solving them :)

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -273 Vote: I do not like it

    I dont know why testers are commenting a lot just for upvotes!? The only thing you done is you participated in a contest few days before most of the people and i dont see anything special to upvote u!

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +569 Vote: I do not like it

      The only thing you done is you participated in a contest few days before most of the people and i dont see anything special to upvote

      Nah this isn't the only special thing about testers.
      He also left one rated contest so that others can enjoy one round.

      → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 3   Vote: I like it +251 Vote: I do not like it

      Down voted, it's not true about many testers, you can't even understand how hard being a good tester is.

      P.S. I feel personally attacked. =(

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it -285 Vote: I do not like it

        Oh my god! Ok i upvoted you becuase its the only thing you want :( and its you third time you are editing your comment to dont get downvote!

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
          ← Rev. 2   Vote: I like it +240 Vote: I do not like it

          What is wrong with you, I want you to understand how important testers are, some of testers duties are :

          1. They should try submitting heuristics/wrong solutions, to make sure tests are strong enough.

          2. They should help problem setters to replace the problems if needed.

          3. They should write many different solutions for a single problem(if needed), to make sure unintended solutions that are wrong or are slow wont pass.

          4. Doing many other things to make sure tests are strong, problems are not spoiled, statements are clear, pretests are fine and etc.

          I saw that your comment has many upvotes, so it probably means many people don't know about testers, so I wrote this to show you how being a good tester is , not for upvotes.

          P.S. I enjoy editing my comments, you cant blame me for that.

          → Reply
          • »
            »
            »
            »
            »
            »
            4 years ago, # ^ |
              Vote: I like it -259 Vote: I do not like it

            Upvoted as i said

            → Reply
          • »
            »
            »
            »
            »
            »
            4 years ago, # ^ |
            ← Rev. 2   Vote: I like it +45 Vote: I do not like it

            Agreed. A good contest is the result of hardwork and collaboration of all testers, problem setters and coordinators.

            I would like to thank all of you for making so many good contests for us.

            Hope to have fun in this contest too:)

            All the best to all!

            → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +229 Vote: I do not like it

      As a tester, I can confirm that we do absolutely nothing in a grand conspiracy to gain contribution points by making meaningless confirmations on the contest announcement.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +35 Vote: I do not like it

        As a non-tester who would very much like to become one, how can I get in on this conspiracy?

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
            Vote: I like it +11 Vote: I do not like it

          Just pretend you're a tester in the comment section, then they'll add you to the tester list in the announcement.

          → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +20 Vote: I do not like it

        I love it when people compose formal responses to jokes.

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +33 Vote: I do not like it

    this is what all testers say about their rounds:))

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +10 Vote: I do not like it

      Wait for the next Global round. :)
      For spoilers about tester comments of next Global join AC.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +107 Vote: I do not like it

    Scam

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +50 Vote: I do not like it

    Proof of a conspiracy theory by testers to gain contribution.

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +48 Vote: I do not like it

    Frequent comments like these is why nobody takes such comments seriously now!

    If you found the questions interesting, you are clearly lying and spamming for contribution. As simple as that.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +30 Vote: I do not like it

      Or maybe they simply should be banned of the tester position as they have a much different taste for problems than the CodeForces community does.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Did some comments disappear? I think I saw few other replies to this comment yesterday.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Yes, nima_oof_che_mamehaii's reply disappeared, and all of the replies to it with it.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 4   Vote: I like it 0 Vote: I do not like it

        Do you think this is intentional or some other bug in the Codeforces website?

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
            Vote: I like it +6 Vote: I do not like it

          Probably intentional.

          → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          Yes,It's intentional..After many negative vote some commment filter out.I think this feature added from past 2 contest ..I think it's a good initiative.

          → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +16 Vote: I do not like it

      Yes. They tried to silence me revealing the secrets about the tester-contribution conspiracy.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it +9 Vote: I do not like it

        Hi i forgot to reply your message when my comments was there. you replied me that you and lots of testers didnt do it! And im gonna say yes! I agree and i was saying some of them are doing it in every single contest and i was replied to tester i think that its not fair! I dont realy care about upvotes and downvites i just say something that i believe so im sory if any one get mad at me becuase if those comments but im saying that these kind of works are not cool :(

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          some of them are doing it in every single contest

          I agree with that, but I'm not one of them, I joke about those things sometimes, but I really don't mind.

          → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +58 Vote: I do not like it

    Codeforces should have option of downvoting comment even after upvoting it.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -14 Vote: I do not like it

      You can still downvote the comment next to that one.

      → Reply
»
4 years ago, # |
  Vote: I like it +209 Vote: I do not like it

I was master when I tested the round, I wouldn't have done it if I knew I would have missed such a great round :((

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

What is the meaning of subtask? Does this mean a problem will have an easy and a hard version?

→ Reply
»
4 years ago, # |
  Vote: I like it +64 Vote: I do not like it

Glad not seeing comment section filled with memes this time

→ Reply
»
4 years ago, # |
← Rev. 5   Vote: I like it -57 Vote: I do not like it

Good luck everyone. This community is insane lol

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +22 Vote: I do not like it

    Here I was wondering why there were so many negative feedbacks until I saw the revision history XD

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it 0 Vote: I do not like it

      I just said I loved physics and people got offended, so had to change. I still don't know the reason

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Its not necessarily that people are offended. They might not agree with your opinion and hence the negative feedback.

        → Reply
»
4 years ago, # |
  Vote: I like it +46 Vote: I do not like it

頑張って皆！Good luck everyone!

→ Reply
»
4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

I love Japan and the Japanese so i'm excited for contest :D

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    High possibility of involving anime characters

    → Reply
»
4 years ago, # |
  Vote: I like it -42 Vote: I do not like it

Hope , we will see Geometry related problem.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Looking forward to this round!

→ Reply
»
4 years ago, # |
  Vote: I like it +16 Vote: I do not like it

Physics is evrywhere :v

→ Reply
»
4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

My UI of codeforces has been shifted to left side and I'm unable to see users and search problems with specific rating, Is there anyone facing the same issue since morning?

→ Reply
»
4 years ago, # |
  Vote: I like it -75 Vote: I do not like it

well all the testers can anyone just give slightest of hints as to what type of problemset is coming our way tommorrow

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 3   Vote: I like it +5 Vote: I do not like it

    What do you think their replies would be ...other than "Some Interesting Problems".

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -62 Vote: I do not like it

      but still it would be much better if we get to know type of problems.maybe tiniest of clues

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +8 Vote: I do not like it

        "maybe tiniest of clues"

        Idk why.. but this sounds so-fuccin-funny..

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    Sure. I was a tester. I can tell you. The problems are interesting. Have fun!

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    I'll give you a hint for the next 100 rounds, I know, even better. You'll see greedy, constructive, more greedy, elementary math, guesswork, and greedy. You only have a chance at an actual cs problem if you can make it to the last problem, otherwise you'll write 20 lines of code since people on a platform called "code"forces do not enjoy coding.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      Let me guess, F is your favourite problem in the contest?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it +7 Vote: I do not like it

        I'm too dumb to get to it. But I saw by your comment you thought it wasn't great ig :(

        But i'd rather code 30m for boring problem (though it is probably not boring for me) than not code at all. So probably.

        → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Highly disagree. There's a fair amount of regular coding at a regular software engineering job. There are tons of "put a twist on a standard CS algorithm"-type problems on Leetcode.

      This is the only place with such a high ratio of actual problem solving / lines of code. Let's keep it that way.

      This contest wasn't the best one, but not because the implementations happened to be short. There are plenty of other contests with problems with similarly short implementations but that were nonetheless elegant and delightful.

      → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +1 Vote: I do not like it

      I agree not many problems related to Binary Search, Graphs Algorithm etc. nowadays....

      → Reply
»
4 years ago, # |
  Vote: I like it -22 Vote: I do not like it

is it unrated?

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 3   Vote: I like it +1 Vote: I do not like it

    It is rated if your rating is strictly less than 2100 !!

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    The answer is both a yes and a no.

    (Did you read the announcement?)

    → Reply
»
4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Dude loves physics so much, he used it as his username, pretty sure some physics related questions,any ways good to have frequent rounds.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    And if tourist were the problem setter you would expect problems themed around sightseeing tours.

    → Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +51 Vote: I do not like it

Add the scoring distribution. If you can solve all the problems in a moment, you'll achieve exactly 10000 pts!

Auto comment: topic has been updated by physics0523 (previous revision, new revision, compare).

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

All the best and hoping for a great round!!

→ Reply
»
4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Thank you for these frequent contests. we keep on learning and testing our skills it's really helpful

→ Reply
»
4 years ago, # |
  Vote: I like it +33 Vote: I do not like it

Do we need to practice HC Verma or Irodov?

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it -42 Vote: I do not like it

    This Comment is Deleted Due to negative feed back, don't know why but my comments are getting down votes all the time, even though the content of my comments are genuine & accurate. From now on I decide to never give any suggestion to anybody on codeforces in the form of comments , because I may not be intelligent enough to give suggestions to most of you.

    thanks!

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +26 Vote: I do not like it

      Dude, it is a pun on the problem setter username

      → Reply
»
4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

I have participated in the writer's contests on another platform (Hackerrank), and his problems are always well-prepared and fun to solve.

I believe this round is going to be great as well!

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +12 Vote: I do not like it

    Do you have a link to his contest(s) there?

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +13 Vote: I do not like it

      Check This.. it's writer is physics0523 .

      → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +13 Vote: I do not like it

      Here is the link to his latest contest.
      Unfortunately problem statements are written only in Japanese, but the problems are like the ones from AtCoder Beginner Contest.

      → Reply
»
4 years ago, # |
  Vote: I like it -12 Vote: I do not like it

A contest a day keeps the pressure away.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

what's the meaning of (1500 + 1250) in scoring distribution for 5th problem ? can't we just write 2750 instead? Thanks in advance !!!

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +1 Vote: I do not like it

Hope these long queues will be solved as fast as possible. And we will have good contest.

And it is solved :) when i returned to submit the problem after writing comment, it was solved.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I'm a beginner in CP and became PUPIL in last DIV 3 contest solving 4 problems. Hoping to do well in this contest too. But the problem I'm facing is I'm able to solve A, B in div 2 but on C I always get stuck. So any suggestions how to cover this gap between B and C?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    I think the only thing you need , is "practice" .I also in your level & stuck on C.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Yes, I am practicing a lot. And when I see solutions of C then most of the time I find a new concept which I don't know and then I try to learn that from youtube or from somewhere else.

      → Reply
»
4 years ago, # |
  Vote: I like it +22 Vote: I do not like it

2 hours remaining to start the round. But wrong division cases on Codeforces Round 653 (Div. 3) is not fixed yet. Some experts get their rating changed. Will it be fixed before the round starts?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Maybe they registered for div3 round before they became expert.So they were not out of competition.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Yes i know that. But as far i know mike fixes it manually at the time of rating change.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -10 Vote: I do not like it

    Who cares?! ))

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Some expert may solve the round carelessly since the round is not rated for him. They might care about unwanted rating change.

      → Reply
»
4 years ago, # |
  Vote: I like it -43 Vote: I do not like it

making the start 25m later would be perfect!

→ Reply
»
4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Hope the contest will be as interesting as the score distribution .

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I hope in this round "in queue" will not be shown for longer time

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

how can someone become a tester .... i want to experience being a tester

→ Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Hlo Guys. I am new here. What is the meaning of score (1500 + 1250) of 5th question?

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Hope to become green

→ Reply
»
4 years ago, # |
  Vote: I like it +44 Vote: I do not like it

I don't like this round at all...

→ Reply
»
4 years ago, # |
  Vote: I like it +78 Vote: I do not like it

And why did Akari have to make the E1 problem difficult? She should have kept quiet. Damn these front bench kids!!

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +91 Vote: I do not like it

No offense to the round writers, but problem B needs to be proofread by a native or advanced English speaker.

Edit: To clarify, I think the problems are interesting as always, but the phrasing and typos make the problem difficult to read for someone not familiar with the idea of the problem.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    I was just going to say this. If there are going to be any rounds in English, it is best they are authored properly. FFS!!

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    Russian statement wasn't great either.

    → Reply
»
4 years ago, # |
  Vote: I like it +43 Vote: I do not like it

Good-bye my rating!

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -72 Vote: I do not like it

Very Bad round with 90% maths

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +116 Vote: I do not like it

    If you call these problems math, show at least one round which isn't math

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -22 Vote: I do not like it

      that's cause all cf rounds are too math based.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +21 Vote: I do not like it

    The first question was basic arithmetic, we can't complain. 2nd question required you to know sum of first n Natural numbers which was also not any tough maths. C was casework, D was pattern. Why are u complaining?

    (pls correct me if I'm wrong somewhere)

    → Reply
»
4 years ago, # |
  Vote: I like it -37 Vote: I do not like it

Mathforces :(

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +57 Vote: I do not like it

It seems like I am the only one who liked the contest. ??? Feel free to downvote if you disliked it. IMHO it is a balanced contest and it is not that MathForces as some of you think.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    I don't feel like it's a mathforces round at all. For me it's just easy problems with many corner cases and very unlikeable implementation. In C 4 i got WAs and my AC code is just 7 if statements

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    For me it felt like mathhomeworkforces. I did not have any programming problem, it was all logic and E some formular.

    → Reply
»
4 years ago, # |
  Vote: I like it +7 Vote: I do not like it

Interesting problems, but Im too bad for them(

→ Reply
»
4 years ago, # |
  Vote: I like it +155 Vote: I do not like it

WTF is going on with this comment section? Round isn't over yet

→ Reply
»
4 years ago, # |
  Vote: I like it -17 Vote: I do not like it

I hate this B why I can't solve it spent the whole time on it :(

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +54 Vote: I do not like it

I'm curious how the testers easily understood problem B and didn't they feel D is too easy for div2D??

→ Reply
»
4 years ago, # |
  Vote: I like it +6 Vote: I do not like it

this contest was difficult for me

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -36 Vote: I do not like it

[Deleted]

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +183 Vote: I do not like it

    Why, so that every time someone has a bad performance they can make the round unrated by uploading solutions?

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      No. That guy was livestreaming his solutions on youtube (from start ). But I'm honest and didn't visit the site and solved what i could myself.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +10 Vote: I do not like it

        I'm not saying that's what happened here. But I am saying that if you make a round unrated if there are cheaters, then every round will be unrated.

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +47 Vote: I do not like it

    It was travisscott as it can be seen at 26:48.

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    That's why number of LOSERS solving problem E increased exponentially suddenly at a certain point of time!!

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      CF predictor shows -2 rating for me, damn if cheating happened like that, I'm happy with this rating xD

      → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +16 Vote: I do not like it

      In the video, only A, B and C were solved (and there were also two failed submissions on D).

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Due to actions of some of these people whole community suffers.Something should be done against them so that this is not repeated.

    → Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

What is the pretest 2 for D?

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +29 Vote: I do not like it

ObservationForces

→ Reply
»
4 years ago, # |
  Vote: I like it +18 Vote: I do not like it

ConstructiveForces

→ Reply
»
4 years ago, # |
  Vote: I like it +108 Vote: I do not like it

Did I accidentally open Codechef today for the contest?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -20 Vote: I do not like it

    how would we know also are you blind?

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +36 Vote: I do not like it

      Codeforces Rule #343: Ignore comments from unrated accounts

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +43 Vote: I do not like it

        Codeforces Rule #434: Ignore comments from Master accounts registered 2 months ago

        → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it -12 Vote: I do not like it

        Irony is you are the one breaking that rule

        → Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I feel bad for the problem writers because of the people who posted the solution to the contest on youtube.

On an unrelated note: is the contest going to be unrated?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Plagiarism is checked I guess. So all those who copied will be anyway disqualified

    Please look into it MikeMirzayanov physics0523

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      Even then, you still could've gotten the gist of the solution of the problem and simply rewrote the code with your own style. It's also extremely difficult (basically impossible) to check for plagiarism if you submit with another language.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +4 Vote: I do not like it

        Especially the first 3 problems were just math formulas which are very hard to be checked for plagiarism.

        → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +57 Vote: I do not like it

      We found the cheater, too. If some users copied some solutions, the plagiarism checker will work.

      I think the contest will be still rated because sadly there are always some cheaters.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Even He cheated with youtube live.But got +543 ..Cheating is easy now :v And my some friend copy and change some variable , not caught by checker ! Is plagiarism jokes ?

        → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +5 Vote: I do not like it

      Don't count on that. it's very easy to beat Plagiarism testing of codeforces.

      → Reply
»
4 years ago, # |
  Vote: I like it +23 Vote: I do not like it

I don't know if this was intended or not, but I literally solved problem B using the samples without thinking in the main problem.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    I did that for A. :) Sample test cases clearly showed (n+1)/2 if one notices carefully.

    → Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Nice contest, easy D. I got pretest 9 failed for problem E1 anyone has a clue about that pretest

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

How to solve D? Greed- fill diagonally then it's left and right diagonal and so on...is giving wrong

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    the idea is ok but when you reach the cell (n-1,n) have to finish with the cell(1,n) and so on (apply modulo when you reach n)

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Try 1 3 6

    Your code will return 4 110 111 011

    while it should return as mentioned: 0 110 011 101

    → Reply
»
4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Was C really just casework? (that's how I did it but..). I hate such questions, wastes time, and morale. Couldn't solve D due to it :(

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +25 Vote: I do not like it

    My observation was that it's always optimal to put all the type 2 people first. The reasoning is that since they always take from the smaller pile, then the size of the pile they'll take from will be $$$x, x-1, x-2, ...$$$ (if $$$x$$$ is the original size of the smaller pile). The larger pile will never be taken by the type 2 people until its size is less than or equal to the size of the smaller pile, resulting the continuation of the sequence. Hence it's never better to put type 1 people first.

    The yes condition ends up being a+b >= n+m && min(a, b) >= m.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      That's it? 1 line of code. I tried caseworking and failed miserably.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        same here wasted lot of time

        → Reply
»
4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

I solved B completely based on the sample cases. I have no idea what does the problem say! I just make it work on samples, I do not know if I am gonna pass system tests or not.

anyways, thanks for the round authors and testers.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +10 Vote: I do not like it

can someone tell me why my E1 solution fails at pretest 9 ?

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

How to solve E1 ? Can someone point me my mistakes ?

int n, k;
vector<int> a; /// size n || sorted
bool solve(int x)
{
    int res = 1;
    for (int i = 0, p = 0; i < n; ++i, ++x)
    {
        while (p + 1 < n && a[p + 1] <= x) p++;
        res = (1LL * res * (p - i + 1)) % k;
        if (res == 0) return false;
    }

    return true;
}
→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +1 Vote: I do not like it

    I think your mistake is in these lines

    for (int x = max(k, mx + 1); x <= n; ++x)
        res.push_back(x);

    You only need to iterate to mx. That's enough. So basically erase these lines

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Yes, removing it give me AC, how stupid I was. Thansk for pointing out my mistakes

      → Reply
»
4 years ago, # |
← Rev. 5   Vote: I like it +6 Vote: I do not like it

In problem B, The picture in sample test case changed during the contest. Initially there were only 3 green ticks. At the end of the contest, there were 6. This created confusion.

Proof-

During contest-Link

When I saw after the contest-Link

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    Yes. The green ticks confused me (no matter how many they had). The clearest representation would be to group the pictures into 4 categories to show which ones are the same.

    → Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Back to specialist, RIP rating -100 :(

→ Reply
»
4 years ago, # |
  Vote: I like it +39 Vote: I do not like it

Understanding problem B's statement alone should be rewarded with +50 rating

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    gimme that rating, I understood the problem in one go. (cuz i read it too slow)

    → Reply
»
4 years ago, # |
  Vote: I like it +33 Vote: I do not like it

I usually don't comment on the quality of rounds, but I think this round was really bad. A — C are just formulas and cases, and D is constructive. You literally could know zero algoritms, even not know binsearch and sorting, and still solve A — D, and this is really bad in my opinion.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

First time I solved 4th, Thanks physics0523, you also gave the overflow details in testcase, thanks for that too, Last time I wasn't able to solve due to overflow.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

I used floor((n-1)/2) + 1 as my answer but this failed on pretest 3. I wonder why? Even in the editorial, same solution is mentioned. I give (n-1)/2 + 1 it passes. Where is the mistake?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    return type of floor is a double type. So if the returned value is large it will be printed in scientific notation (like 5e+008). where as when you do (n-1)/2 the result will remain an integer type and all its digits will be printed as normal integer.

    → Reply
»
4 years ago, # |
  Vote: I like it +252 Vote: I do not like it

F: Think for 0.2 seconds and implement for 30 minutes. What an amazing problem.

→ Reply
»
4 years ago, # |
  Vote: I like it +40 Vote: I do not like it

Weird template but ok

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

rip

→ Reply
»
4 years ago, # |
  Vote: I like it +31 Vote: I do not like it

Most Ad-hoc round I have ever given on CF.

→ Reply
»
4 years ago, # |
  Vote: I like it +116 Vote: I do not like it

Problem B was written terribly and also sample explantions were really bad. I won't say that the round should be unrated but it was one of the worst rounds by far in terms of problem statements.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +12 Vote: I do not like it

    Misunderstood the problem and wasted a lot of time. RIP rating

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      RIP English first... The diagrams were so confusing I just guessed formulas and hoped to get one that works.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    Totally agree. Things were terribly written in the problem B. Was the problem B made to check English and patience of people? One-liner formula was the answer after reading the worst problem statement.

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Exactly. What the hell did the green ticks mean ? He could have simply showed the correct 4 out of 6 in green ticks if at all that's what the author wanted to show. I was scratching my head for 10 min over that.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      yeah, ticks just messed up the statement further

      → Reply
»
4 years ago, # |
  Vote: I like it +51 Vote: I do not like it

Boring contest

→ Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

I hope that someone will have a good proof that why it was optimal to start with type 2 People in Problem C ! I am not able to reason it out! why Starting with Type 1 people is not optimal !

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    My logic was that you can shove your unwanted cookies at type 1 at the end, and they'll eat anything.

    So, you should give your rarer cookies to type 2 people first

    → Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +1 Vote: I do not like it

    Its because type 1 people always chooses the cookie which is left MORE so they will never get angry if a cookie is left no matter v or c. Type 2 people choose the cookie which is left LESS so they will get angry if the cookie which is left less is finished. Attaching my code for your reference https://codeforces.me/contest/1371/submission/85648596.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      i understand the idea ! But during the thought process I had in my mind that during all this If we feed all the TYPE 2 people first their will come a time where The ratio of cookies will reverse ! And That can happen quite some times during this procedure how to deal with it ?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it

        Type 2 people are sadists they will try to eat up the cookies which are already less. So the number of both the cookies should at least be equal to the no of type2 ppl. The ratio won't reverse as type 2 will go on consuming the less cookies making it lesser.

        → Reply
»
4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

What was B? I didn't even go further after reading 4 lines. Highly unclear. Problems must be easy to understand but hard to solve. Seems this was reversed.

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    .

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      What cheating happened ?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it 0 Vote: I do not like it

        .

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
          ← Rev. 2   Vote: I like it +7 Vote: I do not like it

          Its a request to make the round unrated. Worst Problem statements, Lengthy, confusing Adhoc Problems, Round full of cheating. Though my rating is getting a +45, but I don't care, because the round was terrible.

          → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    B was like 5 lines of code wrapped in a ambiguous and confusing problem statement.

    → Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +9 Vote: I do not like it

For question E, I have a claim that the answers are consecutive if there exists any. Can I ask for a proof / disproof of this claim?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Suppose that $$$x$$$ is the smallest positive number where f(x) is greater than 0 (In other words, $$$x$$$ is the smallest possible amount of candies you need to start with so you can beat all the opponents).

    Suppose that $$$y$$$ is the smallest positive number such that if you start with Y candies, then at some point of time, You'll be able to fight at least $$$p$$$ opponents and win.

    The answer lies between [x,y-1] inclusively.

    for any $$$z$$$ < $$$x$$$ has f(z) = 0, so divisible by p, so [0,X-1] is totally unacceptable answer

    anything greater than or equal to $$$y$$$ has f(z) = k * p, which is divisible by p , so [Y,infinity] is also unacceptable answer

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      actually, imo proving $$$f(z) = kp$$$ for $$$z \geq y$$$ is not trivial

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it +3 Vote: I do not like it

        But it's trivial to prove that $$$f(z) = kp$$$ for $$$z \ge 10^9$$$. Since, $$$f(z) = n!$$$ and given that $$$p \le n$$$, $$$f(z) \mod p = 0$$$

        → Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 6   Vote: I like it +10 Vote: I do not like it

    let $$$g(i)$$$ be the number of possible choices of $$$P[i]$$$ ($$$1$$$-indexed) for some $$$x$$$
    you can prove that $$$g(i)$$$ is the same for any valid prefix $$$[1, i - 1]$$$ of $$$P$$$
    obviously the number of permutations is the product of all $$$g(i)$$$
    you know that $$$g(n) \leq 1$$$ (since only 1 integer remains), $$$g(i) \geq g(i - 1) - 1$$$ (because you can still choose all the indices that were valid for the position $$$i - 1$$$, except $$$P[i - 1]$$$)
    so the values assumed by $$$g$$$ are consecutive, and if an $$$i$$$ such that $$$g(i) \geq p$$$ exists, a $$$j$$$ such that $$$g(j) = p$$$ also exists
    an $$$x$$$ isn't valid if there is some $$$i$$$ such that either $$$g(i) = 0$$$ or $$$g(i) = p$$$
    let $$$l$$$ be the maximum $$$x$$$ such that a $$$g(i) = 0$$$ exists, for $$$x' < x$$$, $$$g(i) = 0$$$
    let $$$r$$$ be the minimum $$$x$$$ such that a $$$g(i) = p$$$ exists; for $$$x' > x$$$, $$$g(i) \geq p$$$, so there is some $$$j$$$ such that $$$g(j) = p$$$
    so the only valid answers are in the interval $$$[l, r - 1]$$$
    these values are all valid because $$$l$$$ is maximum and $$$r$$$ is minimum

    → Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 3   Vote: I like it +10 Vote: I do not like it

    Proof by AC: 85713453 (find minimum value in easy O(N), binary search to find the max value that works, print every number in between).

    Will update with my "proof" later.

    Proof:

    • Claim: f(x) can be written as some factorial, lets call it X!, multiplied by some mumbers <=X.
    • You can see that this is true when you calculate $$$p_i$$$, the number of possible numbers to go in the $$$i$$$th spot, after you've determined the first $$$p_0$$$ to $$$p_{i-1}$$$. f(x) equals $$$p_0 \cdot p_1 \cdot \ldots \cdot p_{n-2} \cdot p_{n-1}$$$. $$$p_i$$$ is calclated by (the number of numbers in the array <= x+i) — i. $$$i$$$ increases by $$$1$$$ each iteration, and because that is the only way for $$$p_i$$$ to decrease, is impossible to decrease by more than $$$1$$$. There is $$$1$$$ possible number that can go in the last position because only $$$1$$$ number is left, so the $$$p_{n-1}$$$ must equal $$$1$$$.
    • Thus, say you found the position with the maximum number of possibilities had $$$X$$$ possibilities, f(x) = X! * {some numbers <= X} because all numbers between $$$1$$$ and $$$X$$$ inclusive must be represented in $$$p_0$$$ to $$$p_{n-1}$$$.
    • This is important because you can say that $$$f(x)$$$ is divisible by all primes $$$<= X$$$ and not divisible by any primes $$$> X$$$, where $$$X$$$ is the number of possibilities of the index with the most possibilities.
    • You can also show that the $$$X_a \le X_b$$$ for all $$$a < b$$$. This is because having a greater value of x in f(x) will never result in less possibilities for any position.
    • Thus, for all $$$f(a)$$$ and $$$f(b)$$$, where $$$a < b$$$, if $$$f(a)$$$ is divisible by $$$p$$$, then $$$f(b)$$$ must also be divisible by $$$p$$$. $$$X_a$$$ is $$$> p$$$, and since $$$X_b \ge X_a$$$, $$$X_b > p$$$ as well.
    • Starting from the minimum working $$$x$$$ (before of which $$$f(x)$$$ is all $$$0$$$), no value of $$$x$$$ after the first non-working $$$x$$$ can work, so the answer must be in the form of a continguous sequence of numbers.
    → Reply
»
4 years ago, # |
  Vote: I like it +16 Vote: I do not like it

It is ironical that someone who has physics in his username loves math!!!

→ Reply
»
4 years ago, # |
  Vote: I like it +57 Vote: I do not like it

physics0523 write code for problem F. then he write problem for his code

→ Reply
»
4 years ago, # |
  Vote: I like it +18 Vote: I do not like it

Terrible legends to problems, most of the time was spent on understanding the statesment((

→ Reply
»
4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

A lot of Observational questions. If it hits , you could get AC in 5 mins, otherwise many kept scratching, like me.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Accurately put. That's exactly how it was. Hit the idea or hit the right youtube link. XD

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    I'm pretty bad at Observational questions. Is there any tag related to such problems? I want to solve them. Problem like problem C, I mean.

    → Reply
»
4 years ago, # |
  Vote: I like it -11 Vote: I do not like it

Worst contest ever :/

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -12 Vote: I do not like it

logic in Problem D is the same as this problem from recent div3 contest

https://codeforces.me/contest/1360/problem/G

→ Reply
»
4 years ago, # |
← Rev. 4   Vote: I like it 0 Vote: I do not like it

Can someone explain to me the solution to A? I used n / 2 with ceil.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    ans = n / 2 + n % 2, because if n is odd, then we have 1 + (n — 1), 2 + (n — 2) ... n

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      or simply just (n+1)/2 as languages round down during division.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    print each test-case output in newline.

    → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Use ceil(n*1.0/2) it will work

    In your case, you are using n/2 which will be treated as int and to make it float multiply it with 1.0

    if n=5 your answer will be ceil(5/2)=ceil(2)=2
    but it should be 3 as ceil(5*1.0/2)=ceil(2.5)=3

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      n was declared as float. I used ceil(n/2.0).

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        float can't accurately represent all numbers up to 10^9. Needs to be double or done via integer maths.

        → Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Question B was not clear. In the first sample test case,they should have clarified that the 4th and 5th picture are also same (they have different r thats why they should be different). Wasted more than 1 hour on it (I figured the formula in 2minutes) and could not touch C and D properly. Plz,clarify these things.Even on asking the jury ,it said only the last picture(for 1st sample test case) is not considered but actually the last 3 pictures were not considered in the answer.

→ Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

I hope Editorial has some brilliant solution for F. Otherwise it is one of the worst problems I've seen in a while.

→ Reply
»
4 years ago, # |
  Vote: I like it +12 Vote: I do not like it

I guess it will be hard to believe the testers that comment "problems are very interesting" after this round:(

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Very good round!

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I think that it is in a sarcastic way!

    → Reply
»
4 years ago, # |
← Rev. 4   Vote: I like it +100 Vote: I do not like it

Some of the shortest code for A-C that I've seen...

A: (n+1)/2

B: r >= n ? (n*(n-1)/2 + 1) : (r*(r+1)/2)

C: (a+b < n+m || min(a, b) < m) ? "No" : "Yes"

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    please can you explain the solution of B and C,

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +26 Vote: I do not like it

      B: When $$$n > k$$$, then there are $$$k$$$ different patterns, one starting at each different day of the week. When $$$n \le k$$$, you only have the straight line pattern. So for $$$r \ge n$$$, you get $$$1+2+...+(n-1) + 1$$$. For $$$r < n$$$ there will never be enough days in the week for a straight line, so it's $$$1+2+...+r$$$.

      C: The observation was that it's always optimal to put all the type 2 people first. The reasoning is that since they always take from the smaller pile, then the size of the pile they'll take from will be $$$x,x−1,x−2,...$$$ (if $$$x$$$ is the original size of the smaller pile). The larger pile will never be taken by the type 2 people until its size is less than or equal to the size of the smaller pile, resulting the continuation of the sequence. Type 1 people always take from the larger pile, so you'll only fail if you run out of cookies. Hence it's never better to put type 1 people first. You also need to check if there are enough total cookies for all the guests.

      → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Include D as well :XD

    → Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    B should be (r*(r+1)/2), isn't it? Typo?

    → Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Any idea what does TC4 in E1 looks like?

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +147 Vote: I do not like it

Problem B is absolute trash, super unclear, and boring.
Problem C isn't better. Author, can you tell me what the interesting idea or approach is behind this problem? As for me, it's just about understanding problem statements and implementing stupid case analysis.

You know, >75% of participants solve only A, B, and C. So for them it was a 100% shitty round.

P.S. please never invite AmShZ and noobiesAG as testers anymore, if they find this round "really interesting" and "such a great".

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Solved A in 3 mins from then till now I am unable to cracks B's statement If B & C problems are like that how would anyone solve any on Div 2

    → Reply
»
4 years ago, # |
← Rev. 3   Vote: I like it +23 Vote: I do not like it

Even A,B,C Solution found on youtube after 1 hours+ . Link. Please notice .MikeMirzayanov ..Please find all the cheaters or and if not possible hope this contest will be unrated.I know to make a contest, authors made so hard work,, But It is unfair someone copy the solution and take positive rating before our eyes And someone go down for only cheaters and gain negative rating . .

**N.B: I was not submit any solution cause busy sometimes on the contest time.Now i feel good cause some problem statement was unclear too , specially B..the contest was worst overall.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +17 Vote: I do not like it

    It's impossible to catch cheaters. The first three problems are a simple formula so you can rewrite it however you want. In addition, many people were confused by the problem statement for B. Many questions were asked with disappointing responses. The problems were of really low quality so many people who usually solved the first 3 questions couldn't even solve 2! This would cause the cheaters to get a lot of positive rating change which is clearly unfair to the community. Thus, I think that we should make this round unrated.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -8 Vote: I do not like it

      Listen to the community: looking at the comments I can find only 2 which say that they enjoyed the contest (not including testers who apparently have a different taste of problems than we do). Clearly, the contest is disappointing to a lot of people. This can be shown by the contribution of this blog. 5 minutes ago it was at 713 and now it is 683. I think that this round should be unrated

      → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it 0 Vote: I do not like it

      Its correct.Cheaters solved a,b,c easily.and someone can't solved B with their hard work. So By result cheaters got positive rating and hard worker got negative rating . It's unfair (

      → Reply
»
4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

i solved e2 but i didn t understand problem b:))

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Wow, Problem F is really constructive. Are there any easy solutions to F? I tried to implement the Segment Tree, but it is too hard (at least in my case)

→ Reply
»
4 years ago, # |
  Vote: I like it +43 Vote: I do not like it

B should have tag unreadbale instead of math.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    The statement for B was very confusing.For the whole contest, I thought that every week that divides the total number of days given, results only in one pattern.

    → Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

So beneficial a round to SegTree-addicts.

→ Reply
»
4 years ago, # |
  Vote: I like it +39 Vote: I do not like it

Thanks for writing the round OP. I hope you don't take the hate comments too personally. I especially liked problem E, thought it was a very neat way of combining primes factorization with sorting/arrays.

Hope you can release more rounds and/or problems like this one :)

→ Reply
»
4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

I solved A, B & C in under 30 mins but still, I would say the quality of problems especially B was not good. It was just observation, If you see it you solve it else keep getting more confused reading the statement.

→ Reply
»
4 years ago, # |
  Vote: I like it +12 Vote: I do not like it

whats the need for 6 green ticks. Just show 4 diff figures. so confusing,

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -6 Vote: I do not like it
Спойлер

Can someone hack this submission for E2? This shouldnt work as i only checked if the values were 0, p or 2p.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Problem statement for B is not well written...maybe same for E1

→ Reply
»
4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Increasing the difficulty of a contest just by making questions very big and confusing is just not done. It makes contest rubbish rather than difficult.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +95 Vote: I do not like it

We don't need that frequent contests with that trash problems. Improve the quality of the problems.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -9 Vote: I do not like it

A-B-C were one liners and completely math and observation based.I don't think math based problems are bad but I think at max 1 math based problem is enough for each contest. You shouldn't just be keeping the first 3 problems math based and then on top of that give an easy D problem.

→ Reply
»
4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

I don't like problem B

→ Reply
»
4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Failed horribly and didn't learn a single thing from this contest.

→ Reply
»
4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

Wasted a lot of time on B :( and if the answer is 4 why were there only 3 green ticks in diagram ?

→ Reply
»
4 years ago, # |
  Vote: I like it +14 Vote: I do not like it

Was I the only one who got a PDF statement for the 1371B - Магический календарь during the contest?

I was kinda shocked seeing that O_o

→ Reply
»
4 years ago, # |
  Vote: I like it +48 Vote: I do not like it

I got more confused by the green ticks than the language of B.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I was confused with parallel moves and didn't see the announcement for a while.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      It is written parallel to the calender's sides so that was clear for me.

      → Reply
»
4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

The statement of question B was unclear and the figure made it even worse.

→ Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

I solved the 1st Q in 2 minutes.. 2nd Q in probably an hour and 3rd Q in 5-6 minutes.. The problem statement was very confusing physics0523

→ Reply
»
4 years ago, # |
  Vote: I like it -77 Vote: I do not like it

The round was good. B could've been better.

To the incompetent motherfuckers who think the round was bad, go shove your green/grey/cyan/sexpert ratings up your asses. You are stupid and incompetent, just like me, but at least I am not bitching out here like you assholes. Accept you are pathetic and improve yourself. Your opinion doesn't even count as a div 2 rat, douchebags.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +55 Vote: I do not like it

    Hi. Which am i among "green/grey/cyan/sexpert"?

    I think people who complained about round quality (in discord servers, not only in CF comments) have logical and valid elaborations on why they think they are bad. I think they would be willing to discuss with you if you would ask them about which problems are good/why. I think it is not nice to call people "incompetent motherfuckers" if they are trying to engage in a rational discussion based on facts.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -51 Vote: I do not like it

      I don't want to engage in rational discussions with grey people. They tend to have different(read stupid) rationality.

      What are their points, huh? Too much math? Too much observation? This wasn't math. And observation isn't bad, it's good. These people don't know a dime about anything. They just performed shit, and started their stupid rant.

      I ask you, alright, tell me, what was bad in the round besides issues with B's statement?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 3   Vote: I like it 0 Vote: I do not like it

        this comment was garbage.

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
            Vote: I like it +45 Vote: I do not like it

          Hello

          1) The fact that someone leaked solutions isn't author's fault. I will wait till someone leaks solutions when you host the round to tell that the round was terrible because of cheating.

          2) It's weird to accuse round in being "purely math" if later you tell that you didn't even have a chance to spend time on C or D. E2 and F were purely algorithmic. The only point where I may agree is B's statement.

          3) Competitive programming isn't entirely about knowing algorithms, thinking problems are good. Also, if you say that this round is pure math, please tell which round isn't pure math.

          This round wasn't one of the worst on CF, and I hope you can recognize that

          → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +9 Vote: I do not like it

        Listen You ASS****!,grey people like me perform bad in every round but dont rant afterwards .This round was genuinely bad.

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    Dude, you need to take some lessons on improving your language. Just as you have your opinion, so do others, who are "complaining". Atleast, they are not using such profane language.

    → Reply
»
4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

why ranting on the problem statement tho.. ? i also have hard time to understand it.. but the fact that a lot of people solve A-D under 1 hour, proving that the statement isn't that bad.. dont blame others just because you dont understand things.. what you need is practice..

→ Reply
»
4 years ago, # |
← Rev. 3   Vote: I like it +22 Vote: I do not like it

Editorial is out! Auto comment: topic has been updated by physics0523 (previous revision, new revision, compare).

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

My first submission for problem A in C++ was

ceil(1.0 * n / 2) and got WA.
Does anyone have any idea what is wrong?

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    ceil is not that accurate with large numbers..here it can go upto 10 power 9....so better to use (n+1)/2 instead of ceil...i also got one penalty in it as i also used ceil in the first go

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      it is not that it is not accurate but you have to typecast you can look my submission

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it 0 Vote: I do not like it

        i looked at your solution.... the only difference was that i wrote as follows: cout<<ceil(1.0*n/2)<<endl; ans your was like: cout<<ceil(n*1.0/2)<<endl; so what is the difference b/w the two your got ac but mine showed wa

        edit: i got my mistake..i directly printed the ceil(1.0*n/2) value instead of storing it in a long long variable.

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    maybe because it is printing something like 1.06657e+06.

    → Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

How do people made formula for B? What made you think that way ?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    As long as you have more tasks than days in the week you can make a different shape by starting on each day of the week. So you have 1 option for a 1 day week, 2 options for 2 day week etc. Therefore you just need the sum of increasing integers which is a well known (or easily findable) equation (n*(n-1))/2.

    Once you get to the same number of days as tasks the only option is a single flat line that will be the same shape for any number of extra days. So you just add 1 to the above result.

    → Reply
»
4 years ago, # |
  Vote: I like it +38 Vote: I do not like it

in my opinion data structures and algorithm problems have completely vanished in recent rounds and even E problems are coming adhoc and greedy type.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I thought of D as filling largest diagonals. Any flaw in this logic?

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    testcase
    4 12

    your answer

    8
1110
1111
0111
0011

    correct answer

    0
1110
0111
1011
1101
    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -8 Vote: I do not like it

      How did you come up with this pattern? It doesn't seem that obvious. Did you print out all the combinations and then see?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        I tried to reach $$$0$$$ with $$$k$$$ multiple of $$$n$$$, by putting $$$k/n$$$ ones on each row and on each column. It turned out that it's possible.

        → Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 3   Vote: I like it 0 Vote: I do not like it

    N=5 , K=10
    Your Solution
    11100 01100 00110 00011 00001
    Your Answer = 4+4 = 8.

    Actual Answer
    → Reply
»
4 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Glad I didn't upvote this round before the contest.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

please do not convert codeforces into hackerearth. codeforces is authentic site for CP.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -32 Vote: I do not like it

@MikeMirzayanov I would like to thank you for this wonderful platform. I understand that you want to bring the maximum amount of rounds as possible and people complain if rounds happen after many days. But, I think the community will agree that we would benefit more from lesser rounds which are higher in quality as compared many rounds with a high variation in quality.

TLDR: please value quality of contests rather than quantity.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +23 Vote: I do not like it

    I think this is a tester problem, not a Mike problem. Codeforce needs a consistent set of testers who are not afraid of weeding out bad problems and/or contests. If contest writers keep asking their friends to test rounds and the friends are too afraid of criticizing the writer, we have shitty questions.

    I don't see why we can't have many rounds of high quality.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +89 Vote: I do not like it

      There were complaints by testers about the round. For example, after I complained about the explanation for sample 1 of Asterism being wrong, it took about 2 weeks(maybe more, I don't remember) to be fixed. After Monogon complained about parallel moves in B not being explained, nothing was done. I also complained about the quality of C and F.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +14 Vote: I do not like it

        Wow, didn't know that. Thank you for letting me know about the complaints.

        With that said, there should be a veto process where testers can block questions from being used in a contest if there are unresolved issues with them. Otherwise, testing will just become a ceremonious event that no longer improves the problems.

        → Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +32 Vote: I do not like it

For me only problem B's statement had a problem, and even that one was pretty minor. I'm sorry that this one issue colored people's perception of the rest of the contest. In fact the problem setter did a great job of setting appropriate difficulties (see the gradual decline in number of accepted solutions, with no severe drops), and made quite original problems.

My advice for problem B's statement would be to state clearly that the weeklength is constant for each shape (i.e, you cannot say week 1 has $$$4$$$ days and week 2 has $$$2$$$ days). However staring at the first example resolves that immediately.

There are many bitter Dunning-Kruger-afflicted people in the comments. You did a good job.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Oh okay. So now according to this person, every person who found problem B difficult to understand is an overconfident incompetent asshole who overestimates their ability. Right. Good going. I wonder how in almost any other Div2 contest there are no such people complaining about the initial few problems.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Nope, I didn't say that. In fact I shared how I found that statement difficult to understand. But I'm not responding by saying "worst contest ever" because I have > 1 ounce of perspective. I tried to share a way that the setter could improve the statement and a way that contestants could bypass the difficulty (look at the given examples).

      → Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -36 Vote: I do not like it

Absolutely shitty round! I felt like I was participating in a math competition. This round should be made unrated because of the cheating and the low quality problems. Period.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Just because you could not solve the problems? Grow up, dude.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
      ← Rev. 3   Vote: I like it 0 Vote: I do not like it

      Because I found that the problems were basically about observation and I have my right to comment about the standard of the contest. And if you read the comments above, you will find out that other people also found this round below standard. And I solved 2 problems and for your kind information , I commented not because I couldn't solve but because the round was absolutely the worst round in codeforces history.

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it

        I agree the second and third problems were sub-standard. But not every contest can be great. Some contests here and there are bound to be average. And that is no reason for demanding the round to be unrated.

        → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -20 Vote: I do not like it

    Worst contest ever

    → Reply
»
4 years ago, # |
  Vote: I like it +9 Vote: I do not like it

can i submit the code after contest////

→ Reply
»
4 years ago, # |
← Rev. 3   Vote: I like it +3 Vote: I do not like it

Worst Problem statement for B in the history of codeforces. There was only 4 or 5 line solution of B if you clearly understand it.Codeforces problems are known to be easy to understand and tough to figure out the solution but this was exact opposite case. I solved A and C but it took it more than 1.5 hour to understand problem B. I wish i could also figure out the solution by looking at the sample test cases just like others did. * sigh *

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +8 Vote: I do not like it

    also E2 can be solved in 5 lines

    Solution

    honestly I didn't like the problems, they were too observation based.

    → Reply
»
4 years ago, # |
  Vote: I like it +27 Vote: I do not like it

Can people who are demanding the contest to be unrated shut up? By your logic, all I have to do to make the Global Round scheduled in a few days unrated is to upload a YouTube video during the contest. If it goes like this, then theoretically every Codeforces Round will be unrated from now on if even one person is willing to ruin the spirit of competition.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it -25 Vote: I do not like it

    But not only was there cheating in this competition, the problem statements were bad and the problems were of low quality. Although the cheater only solved 3 problems (thank goodness), that still gives almost all cheaters a positive rating change as those who legitimately tried solving the problems had much difficulty in even understanding B! This is unfair for those who didn't cheat and due to the type of the problems, catching the cheaters is basically impossible. With all those factors above combined, I think it is reasonable to request the round be unrated.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I don't think any contest has ever been unrated because the problems were low quality (unless ofcourse when there is some issues with the problem or the judge).

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it +2 Vote: I do not like it

        I don't think you've ever taken into consideration that in this contest, there are both cheaters and low quality problems. This causes cheaters to have a high positive rating change while those who play fair have negative rating change. Clearly, this is unfair to those who don't cheat and, if the contest remains rated, is basically telling everyone "Hey, do you want a positive rating change? Go Google the answers for this round or post them yourself!". This is probably not what you or I want and so, for this reason, the round should remain unrated.

        → Reply
        • »
          »
          »
          »
          »
          4 years ago, # ^ |
          ← Rev. 2   Vote: I like it +19 Vote: I do not like it

          I have never cheated and will never cheat and I will get a huge positive delta change and become CM. The statement is clear for all problems. Maybe B took time to understand because of the nature of the problem that cannot easily be written in a short statement. Though, the image clarified it as much as possible.

          Edit: The number of people who actually cheated would be considerably low according to the amount of participants. No need to make round unrated except in critical situations. I am not defending because of my rating increase, but I am defending because there is no a major reason for making this contest unrated by any means.

          → Reply
          • »
            »
            »
            »
            »
            »
            4 years ago, # ^ |
              Vote: I like it -11 Vote: I do not like it

            Yes. Maybe you are good at reading and you aren't confused by the problem statements but it appears that most users were confused by the problem statements. The images for B completely threw me off. What were the tick marks supposed to mean? In addition, the problem themselves (ignoring the wording as of now) were not too good. Problems A-D were simply just observations. With a great math background and knowledge of I/O, operators, if statements, and for loops, you could solve all the problems. The nature of the problems being Ad-Hoc caused many users to perform worse than they usually do. In addition, many people watched the YouTube video and cheated. When I looked at it (a minute after the contest), the video had 600 views, meaning 600 cheaters who stole the positive delta of others. This shouldn't be encouraged, and to show our determination to prevent cheating, this round should be unrated.

            → Reply
            • »
              »
              »
              »
              »
              »
              »
              4 years ago, # ^ |
                Vote: I like it +3 Vote: I do not like it

              I looked after the contest too and it was just 301 views at that time, I'm guessing the number of people that actually used the info from the video would be even lower.

              → Reply
            • »
              »
              »
              »
              »
              »
              »
              4 years ago, # ^ |
                Vote: I like it +4 Vote: I do not like it

              So, that means, everytime someone uploads a video during a contest would make the contest unrated? Then all contests should be unrated then. I heard there are a lot of cheating groups. Usually, the cheaters are noobs. Newbies-Specialists and sometimes Experts. But, I have rarely seen a cheater CM+. So, it is not a big deal. Already hundreds cheat every round not only this round. You said 600 viewed the video, doesn't mean 600 cheated. Lets say only half cheated which is 300. Which is nothing compared to the amount of people. Ad-hoc problems are really okay. Who said they are not allowed? Ad-hoc are the most common problem types in most platforms. So you cannot really complain about that.

              → Reply
              • »
                »
                »
                »
                »
                »
                »
                »
                4 years ago, # ^ |
                  Vote: I like it 0 Vote: I do not like it

                Yes. I'm not saying Ad-Hoc isn't allowed but it's the fact that the cheaters are going to win that's disturbing the community. If we don't do any action (it's hard to do much other than make the contest unrated), we are silently encouraging the growth of cheaters. I'm sure you don't want that, right?

                → Reply
                • »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  4 years ago, # ^ |
                    Vote: I like it +4 Vote: I do not like it

                  And if we made the round unrated, then all other incoming rounds will also be unrated! We will encourage cheaters! Plus, most of the noob cheaters got their solutions skipped. Maybe a few passed like only 50 passed. This is nothing. Like literally nothing. Not to mention that one of the educational rounds A,B,C,D were copy-pastable from internet(and I saw the sources myself) and the round remained rated.

                  → Reply
                • »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  4 years ago, # ^ |
                    Vote: I like it 0 Vote: I do not like it

                  I think that you, along with the OP both are making this mistake. You are simply arguing that we shouldn't make the contest unrated because of cheaters and we shouldn't make the contest unrated because of bad problems. The thing is that you haven't argued for why we shouldn't make the contest unrated because of cheaters and bad problems.

                  → Reply
                • »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  4 years ago, # ^ |
                    Vote: I like it 0 Vote: I do not like it

                  And I don't see why you didn't mention that you solved B in 13 minutes and couldn't solve C/D.

                  Problems you can't solve aren't necessarily bad. Yes, A-C was basically one liners today, and D was an easy implementation. That might make the problems easier, not bad.

                  And what you are trying to establish will result in Codeforces becoming a very welcoming for cheaters and toxic people. If you can't solve anything other than A, just upload A on YouTube and bam, it gets unrated.

                  → Reply
                • »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  »
                  4 years ago, # ^ |
                    Vote: I like it 0 Vote: I do not like it

                  Problem D solved by 4k participants is bad, change my mind:) Anyway I agree with you, but for some reason my comment written earlier, than whole topic, was downvoted(

                  → Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    I totally agree with you. Making contest unrated will give strength to the idea that, to make round unrated just upload some solutions on Youtube or any other platform during contest. It is totally unfair for majority of contestant who have solved problems fairly.

    → Reply
»
4 years ago, # |
  Vote: I like it -8 Vote: I do not like it

Thanks for the contest, I think it would be better if it was Div 3 contest.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    "I think it would be better if it was Div 3 contest." what's the reason for ?

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      problems(A, B and C) are math and logic problems, problem D is an implementation problem

      → Reply
»
4 years ago, # |
  Vote: I like it +20 Vote: I do not like it

Loved the problemset! Thank you for an interesting round :orz:

→ Reply
»
4 years ago, # |
  Vote: I like it -28 Vote: I do not like it

Worst Contest i have ever given

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +19 Vote: I do not like it

I felt the problemset was a bit Intimidating at first but after giving some thought to every problem, they seemed getting very simple. Really liked this problem set very much as solving the problems felt very very satisfying.

Will be waiting for many more rounds from physics0523 :)

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Agreed, so simple problems so difficult statements. I cannot understand why people like this contest, it has so little value. Really, what can anyone learn from it?

    → Reply
»
4 years ago, # |
  Vote: I like it -34 Vote: I do not like it

Can someone help me find out what is the issue in my code for problem D — matrix

my idea is to fill diagonally. first we fill from 0,0 to n,n. Then we fill two other diagonal which are n-1 lengh and parallel to first diagonal. this way we can keep feeling matrix diagoannly.

package codeforce.div2.r654;

import java.util.Arrays;
import java.util.Scanner;

public class ProblemD {
  public static void main(String[] args) {
    try (Scanner sc = new Scanner(System.in)) {
      int t = sc.nextInt();
      for (int tt = 0; tt < t; tt++) {
        int n = sc.nextInt();
        long k = sc.nextInt();
        int[][] matrix = new int[n][n];
        int length = n;
        int startx = 0;
        int starty = 0;
        int turn = 0;

        for(int i = 0; i < length && k > 0; i++) {
          matrix[startx++][starty++] = 1;
          k--;
        }
        length--;
        while(length > 0 && k > 0) {
          startx = 0;
          starty = turn + 1;

          for(int i = 0; i < length && k > 0; i++) {
            matrix[startx++][starty++] = 1;
            k--;
          }
          
          startx = turn + 1;
          starty = 0;

          for(int i = 0; i < length && k > 0; i++) {
            matrix[startx++][starty++] = 1;
            k--;
          }
          
          turn++;
          length --;
        }

        for(int[] a : matrix) {
          for (int b : a) {
            System.out.print(b + " ");
          }
          System.out.println();
        }
      }
    }
  }
}
→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Next time use spoiler or link option Please.

    → Reply
»
4 years ago, # |
  Vote: I like it +155 Vote: I do not like it

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

https://www.youtube.com/watch?v=fiPIWx88o_8 OMG. Is this the first time this has happened?

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

When I checked travisscott's video with solutions(it was right after the round), it had had about 400 views. Сonsidering that not everyone cheated, we can assume that ~300 participants cheated. The round has 14401 rated participants, so it doesn't affect to overall rating changes enough to make this round unrated.

UPD: ok, who downvotes me, ask yourselves: how does these cheaters hurt me? Why do I care about their rating, when they'll lose it in sequent rounds? And finally, what benefits they have from their cheating if they could become only low-rated cyan? So, realize that you overestimate the harm of this situation, cheaters are bastards and cheating is a really important problem on cf, but unrated round won't help to fix it.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Someone please explain the solution for D

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    keep adding 1's along diagonals

    Eg for 4,5 u get 1000 1100 0010 0001

    4,6 1000 1100 0110 0001

    4,8 1001 1100 0110 0011

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Can you please explain the 3rd case(4,8)

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        see at 4,7 u get 1000 1100 0110 0011

        only column 4 and row 1 has sum=1 rest all have sum=2 so next 1 will go at 1,4 similarily u can extend other diagonals.

        → Reply
»
4 years ago, # |
  Vote: I like it +24 Vote: I do not like it

This is not the first time people raising the bad statement issue where isaf27 was the coordinator. Remember Codeforces Round #637 — Thanks, Ivan Belonogov!? I am no one to judge him.I hope he will be more careful about the problem statement in his future coordination.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

In A Nutshell this round was bad and we know that this could've been better because everyone around have given so many interesting contests all we could do is ask for more consistency and some better and interesting problems.

→ Reply
»
4 years ago, # |
  Vote: I like it +3 Vote: I do not like it

for me, e was way too good than d. don't know why I always got stuck with such kind of problem. I am too noob at it.

→ Reply
»
4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

I solved the 1st Q in 2 minutes.. 2nd Q in probably an hour and 3rd Q in 5-6 minutes.. The problem statement was very confusing physics0523

→ Reply
»
4 years ago, # |
  Vote: I like it -24 Vote: I do not like it

Codeforces is getting shittier everyday, It was a lot better in older days.

→ Reply
»
4 years ago, # |
  Vote: I like it +18 Vote: I do not like it

It is encouraging to be able to solve more questions, but in long term, it dampens the learning process. We already got Div 4 to encourage newer participants, and Div 3 too. The previous Div 2 have been easier. Having one liner and implementation for C and D really does not help much since A and B are usually these. It will be better if C and D introduce us to a new concept or difficult one.

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it +13 Vote: I do not like it

As a participant who usually solves A — D in Div. 2 contests, I agree that there should be some data structure problems. I think it would be fine to have some problems just be ad hoc, but I correctly applying data structures is also a very important. Here, only F was a data structure problem.

→ Reply
»
4 years ago, # |
  Vote: I like it +26 Vote: I do not like it

When will the ratings update?

→ Reply
»
4 years ago, # |
  Vote: I like it -21 Vote: I do not like it

Remember those days when codeforces rounds' had some good or even normal level data structure, dynamic programming, algorithm related problems in problems D, E and sometimes in C? Well, judging by the recent rounds, it seems these type of problems are almost completely vanished in problem (A-E). You don't actually need any knowledge of any algorithm, just some adhoc skill will work. Hell, I can't remember the last time i needed to use any dp in recent rounds.

To be honest I think it's terribly wrong. It inspires especially those people who are obsessed with rating. They would rather practice adhoc tasks than learning any new algo/ds at all. From real life experience, I know some people who think they are good just because they have good rating on CF. But I'm quite sure, their performance will be pretty bad even if they are given some normal algo/ds/dp tasks. (I don't mean they're bad, they just don't practice other than adhocs. Some of them can't even write a recursive dp solution to be honest, but they're purple on CF.)

I just wish the problem set was more diverse as it was rather than solving some adhoc tasks almost in every rounds.

Sorry for my excellent English. My real account is blue-purple.

→ Reply
  • »
    »
    4 years ago, # ^ |
    ← Rev. 3   Vote: I like it 0 Vote: I do not like it

    Some of them can't even write a recursive dp solution to be honest, but they're purple on CF

    lol, do you really think that if somebody can consistently solve DE level adhoc problems, they can't figure out how to write recursive dp? Also today's round had 2 non-adhoc problems (F was pure data structure problem without any ideas), which is normal amount imho.

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it -17 Vote: I do not like it

      First of all, I didn't say that they can't figure out how to write recursive dp. Ofcourse they can. They're smart people. I said that they can't write it because they don't practice this type of problems. But surely it's not applicable for everyone.

      I said it about those people who have started CP in the recent couple of years. (that includes me too.) They depend more on Codeforces than any other platforms (atcoder is a good one too though.) for practice. They usually verify their progress usually by their rating. And it's not good when someone thinks "Oh! I actually don't need to be much skilled on algo/ds to be purple. I just have to practice lots of adhoc problems." Believe me or not, I know some people who think like that. I wish you could see my surroundings. Don't you agree they should practice algorithms & data structures too where actually these are the basis of programming?

      And 2 non-adhoc problems out of 7? Really?? Are you honestly satisfied with this kind of diversity in the problem set? Where (A-E1) are nothing than just a bunch of adhoc problems?

      → Reply
      • »
        »
        »
        »
        4 years ago, # ^ |
        ← Rev. 2   Vote: I like it 0 Vote: I do not like it

        I actually don't need to be much skilled on algo/ds to be purple.
        If you can't solve even one problem solved by most people your rating will heavily fall down. So if you can't solve dp problems, you won't be able to be stable purple because dp is frequent enough to appear on rounds.
        And 2 non-adhoc problems out of 7?
        AB (or ABC in 6 problem rounds) don't contain any ds\algo in most contests anyway (it's beginner level problems), so it's like 2 problems out of 4 that isn't adhoc.

        → Reply
»
4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

when will the ratings be updated !!!!!!.

→ Reply
»
4 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Lesson of the Day- Don't use translator to translate problem statements.

→ Reply
»
4 years ago, # |
  Vote: I like it +15 Vote: I do not like it

I stayed up to witness me becoming purple.I go to bed now,wake me up when rating updated.

→ Reply
»
4 years ago, # |
  Vote: I like it +6 Vote: I do not like it

physics0523 why is the ratings updates slow?

→ Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Most of the comments here are about Video Solutions on Youtube ! LOL It will be appreciated if someone solves till F or Upsolves it and then Uploads a video tutorial ! for problems, i suggest no new channel now guys ! Try to explain hard problems through videos

→ Reply
»
4 years ago, # |
  Vote: I like it +31 Vote: I do not like it

If this contest becomes unrated then every time someone's contest is going bad, they will have the option to make a video and make the contest unrated. We should rather catch cheaters.

→ Reply
»
4 years ago, # |
  Vote: I like it -17 Vote: I do not like it

worst round ever!!

→ Reply
»
4 years ago, # |
  Vote: I like it +11 Vote: I do not like it

Why ratings are not getting updated? Hope this contest does not become unrated, otherwise each time someone will get make the contest unrated. Rather catch the culprit and make sure this does not get repeated in the future.

→ Reply
»
4 years ago, # |
  Vote: I like it +19 Vote: I do not like it

Don't forget to report this video

Can't find appropriate option lol
→ Reply
»
4 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Check out the video editorials:

E1. Asterism

D. Grid-00100

C. A cookie for you

B. Magical Calendar

A. Magical Sticks

→ Reply
»
4 years ago, # |
← Rev. 2   Vote: I like it -6 Vote: I do not like it

I was hoping to participate in today's contest but decided against it after reading problem A. Even though I guessed what the problem was asking, there were gaps and potential for error. I was worried that if problem A had multiple issues in the writeup, then further problems could be even more problematic to understand.

Specifically, take this from Problem A: "Two sticks, that were used in the operation disappear from his set and the new connected stick appears in his set and can be used for the next connections."

It sounded to me that once you connect two sticks to get a new stick, you can continue repeating the combining process with this new stick until you're left with no two sticks of the same size. Of course that would be a harder problem for a Div 2A, and the last example proves otherwise. But the point is that the problem statement was ambiguous and clearly there was a language barrier.

Just as we have testers testing the accuracy of a solution, there should be proof readers — native speakers of the language who are focused on ensuring the brevity and accuracy of the problem statement. Problem writers do a difficult job of thinking up new problems (also remember that this was physics0523's first time as an author, he will only get better with time) and should be focused on that more than anything. I'm certain they could use the help in terms of problem writing, especially if the language in question is not their native language. This will help the problem writer grow their communication skillset as well.

Also, perhaps there can be more standardization in the difficulty of problems. A Div II problem B from one author should more-or-less match up to a Div II problem B by a different author.

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    It sounded to me that once you connect two sticks to get a new stick, you can continue repeating the combining process with this new stick until you're left with no two sticks of the same size.

    Yes, you can, but you must maximize count of stick equal size, so that is wrong tactic. (If this repetition could somehow affect the answer, then please give a specific case)

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Oops, I stand corrected then — your point is valid and it was my oversight in making the claim about problem A.

      Based on past experience, I would still advocate for the concept of proof readers to improve the overall experience.

      → Reply
»
4 years ago, # |
  Vote: I like it -9 Vote: I do not like it

So guys didn't perform well on this contest. Stop complaining and keep training until you get your desired rating. Good luck yall

→ Reply
»
4 years ago, # |
  Vote: I like it +5 Vote: I do not like it

This person should get his/her punishment https://www.youtube.com/watch?v=fiPIWx88o_8

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    He got +543 instead of got banned. xD

    → Reply
    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I mean... 500 + 43... That's just sad for him, the best time for getting huge rating increases, and he just only got +43

      → Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why do you have to make questions which has nothing to do with coding skills at least till question D?We just have to apply mathematics derive a formula and write a 5-6 line code. This is not a Codeforces standard I fell in love with.

→ Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

can anyone please explain Statment of B, i am not getting it clearly

→ Reply
  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Try to read the clarifications also. The statement wasn't clear.

    → Reply
»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

The problem statements were very bad. Worst experience. :)

→ Reply
»
4 years ago, # |
  Vote: I like it +8 Vote: I do not like it

I see a lot of hate in the comments for the problem setter. I did find the problem statement B to be very confusing but the contest was good. Agreed that if you didn't stumble upon that one important intuition/observation it would have been hard to solve it. Then again this is a skill that needs to be attained and a great skill to have in your repertoire. Thanks physics0523 please continue setting awesome problems.

→ Reply