AlFlen's blog

Codeforces Round #662 (Div. 2)
By AlFlen, 4 years ago, translation, In English

Hello, Codeforces!

74TrAkToR and I are glad to invite you to our Codeforces Round 662 (Div. 2), which will be held at Aug/07/2020 17:35 (Moscow time). The round will be rated for all the participants with rating strictly less than 2100.

The problems were created and prepared by AlFlen and 74TrAkToR. We would also like to thank everyone who helped us a lot with round preparation.

On the round you will be asked to help main ponies from My Little Pony animated series (Fluttershy, Applejack, Twilight Sparkle, Pinkie Pie, Rarity, Rainbow Dash) and to solve 5 problems, one of which has two subtasks. You will have 2 hours to solve them.

Score distribution will be announced shortly before the round.

UPD: Score distribution: 500 — 1000 — 1500 — 1750 — (1500 + 1500)

UPD2: Editorial

We wish you good luck and high rating!

  • Vote: I like it
  • +229
  • Vote: I do not like it

Comments Comments (539)
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4 years ago, # |
← Rev. 3   Vote: I like it +119 Vote: I do not like it

As a tester, give me contribution, please:) UPD:( UPD1:)) Thanks you.

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    4 years ago, # ^ |
      Vote: I like it +115 Vote: I do not like it

    Unrelated question: How to become a tester?
    I'm asking for real, not for gaining contribution. ;)

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      4 years ago, # ^ |
        Vote: I like it +46 Vote: I do not like it

      Basically, testers are friends of the authors. Also, some testers are people with a lot of contribution.

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        4 years ago, # ^ |
          Vote: I like it +124 Vote: I do not like it

        As we can see, people with negative contribuion can become testers too.

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        4 years ago, # ^ |
          Vote: I like it +73 Vote: I do not like it

        Aahhh! I see.
        Going to google now "How to make friends in codeforces". ;__;

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          4 years ago, # ^ |
          ← Rev. 2   Vote: I like it +23 Vote: I do not like it

          For making friends in codeforces there is a star in the profile page next to the handle!

          More seriously, it is good to be a friend of the author IRL.

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

            LMAO, I know how to add friends in cf lol. By doing that how will the other person know I've added him as a friend.
            I was referring to getting in touch with contest hosters and problem setters.

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

        err I think you got it wrong.

        The reason testers have high contribution is because they gain contribution after being a well-reputed tester, not necessarily because they started with high contrib.Basically, testers gain contrib, so to say all testers need to start with high contribution is a logical fallacy.

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      4 years ago, # ^ |
        Vote: I like it -23 Vote: I do not like it

      You can ask about it MikeMirzayanov or if you know problemsetters you can ask they.

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      become tourist. then everyone will want you to test. the end.

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

    u dont have idea how ugly the question statements are and kind of worthless .

    Shittttiest contest ever

    writing this while contest in undergoing predict my frustation level..

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      4 years ago, # ^ |
        Vote: I like it -7 Vote: I do not like it

      You can't even solve div3 problems. stop bashing.

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        4 years ago, # ^ |
          Vote: I like it -72 Vote: I do not like it

        Yea i can see who is saying this the one having 12000 rank in prev div 2 contest .Keep up the good work .

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          4 years ago, # ^ |
            Vote: I like it +34 Vote: I do not like it

          At least I was able to solve 3 problems in div3 round where you cheated.

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            4 years ago, # ^ |
              Vote: I like it -111 Vote: I do not like it

            See how much spare time u do have checking on random peoples u wanna be one on one ping me we will talk there . Crybaby there is an iitian in the house

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              4 years ago, # ^ |
                Vote: I like it +32 Vote: I do not like it

              What's the point of being an IITian if you still have to cheat?

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

                Maybe he is of reserved category, lol

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                  4 years ago, # ^ |
                    Vote: I like it -35 Vote: I do not like it

                  Yeah i am if u are such a racist thiugh u should know in india caste discrimination is a crime .

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

                  Dude, you got the seat because of your caste. Why do you expect others to not call you a reserved category guy?

                  Deserving people sacrificed their seats so that you can study there.

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

                  sorry

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

                  thoufond
                  You know you can be punished under the provisions of the Scheduled Castes and Scheduled Tribes (Prevention of Atrocities) act, 1989?

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              4 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it

              Bro!! It is a humble request .. Please don't lower the standards of IIT's in our country unless you are from reserved category(PS: then you took the seat of other deserved candidates due to some shitty political policies). If you are an IITian.. good for you but then if you need a tag on your shirt stating that.. sorry bro you don't deserve it. PS: I was deeply frustrated after reading your shitty comments and so had to write all of it.

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            4 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            Does 'skipped' means that he cheated?

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              4 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it

              Yes

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                4 years ago, # ^ |
                  Vote: I like it -52 Vote: I do not like it

                Ya ankit i respect your words but the thing is i submitted one of my friends solution coz i wasnt willing to go further in the contest as i got some work i heard somewhere that if you copy someones code the contest will be unrated thats all i did . And i dont know what is the point of this guy to just poke in my comment worthlessly out of nowhere kinda frustating already the contest was not up to the mark so thats all .. Anyways i feel bad about my prev comment :) thanks dude

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

                  yeah sure, you submitted for the 3 problems for it to be unrated and not for only one or two problems :)

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

            Thanks, you helped me find my food.

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

      It wasn't unreadable though..

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

    As a tester , were u able to understand the problems ?

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

    The Pretests of question number 2 should be strong. My code Passed pretests but failed after. I am just giving feedback and not complaining. It's real heartbreak to see that red written "System test fails"!

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4 years ago, # |
← Rev. 2   Vote: I like it -102 Vote: I do not like it

!

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4 years ago, # |
  Vote: I like it +29 Vote: I do not like it

Why 6 ponies but 5 problems?

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

Nice pic for seek attraction!!

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4 years ago, # |
  Vote: I like it +37 Vote: I do not like it

I feel old now ;)

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

I love watching "My Little Pony" cartoons, so I look forward to this contest!

But I am not a girl ;)

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

    Me too. It's great but seems not to have more stories :(

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

when a newbie like me see a contest has 5 problems, Oh no this means I will only solve 1 or 2 maximum :/

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

This cartoon is interesting and I hope the problems are short and interesting too!

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

As a participant , give me contribution .

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

What are all the possibilities when a contest submission gets "Skipped" ?

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    All possibilities except when no one cheats.

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      So if we ensure no one takes my code, it won't get skipped, is it?

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

        Yes, avoid using online IDEs like ideone, because if you forget to make the code private by any chance, anybody can access it. Also, you mustn't intentionally give your code to anyone.

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          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          But how can anybody get ideone public links? The person has to share the link right?

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            4 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            No, I guess it's available on the site only, something like recent public actions is available there.
            Actually it happened to me one time when I started CP and used ideone then. In a Codechef Lunchtime, after someday I got an email that my submission got plagiarised due to same code matching with 2 other person's submissions. When I took a look at their codes, their codes were clearly my code with some added unnecessary comments. At that time I came to know about this ideone public access thing.

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

              Currently, Ideone has removed the pubic link of recent submissions which may lead to a decrease in cheating on CP platforms via ideone.

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                4 years ago, # ^ |
                  Vote: I like it 0 Vote: I do not like it

                Ohh, I didn't know about that. Haven't used ideone for the last 4-5 months. Nice to hear it though.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    If your code matches with anyone...if you copy from other or someone copy from you...both of you guys's submissions will be skipped :3

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

Is series is available in YouTube :-)

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4 years ago, # |
  Vote: I like it +60 Vote: I do not like it

Typo: Pinkie Pie is not Pinky Pie.

Also that's a good theme! (I am a brony)

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

    omg, I'm sorry... I fixed it by the way.

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

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

AlFlen If possible can you guys please add some kind of divider between the fairy tale and the problem statement so that people who are only interested in the problem statement can directly jump into it? no offense just a suggestion

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    4 years ago, # ^ |
      Vote: I like it +78 Vote: I do not like it

    We tried to make statements rather short. The legend doesn't occupy a noticeable part of statements so I think it'll be comfortable enough for you to read and understand them.

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4 years ago, # |
  Vote: I like it -15 Vote: I do not like it

one of which has two subtasks. That's interesting !!

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

The second pony from the left does codeforces rounds :GWagnwChinoWoah:

pic-selected-200806-2040-34

Orz

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

i dont like pony

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

Hope it will be queue free contest..

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

    Yeah, we don't want the system to stall.

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

My daughter loves My Little Pony, she should take care of this round...

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    4 years ago, # ^ |
      Vote: I like it +41 Vote: I do not like it

    Parents are doing codeforces nowadays. Damn! Thats why I love codeforces

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      4 years ago, # ^ |
      ← Rev. 2   Vote: I like it +5 Vote: I do not like it

      from 5th standard Russian students to parents, from newbie to world top coders, you will get each category on codeforces. That makes competition more interesting.

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

Hi ainta!

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    4 years ago, # ^ |
      Vote: I like it +214 Vote: I do not like it

    As a testers, I'm not a tester :)

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4 years ago, # |
  Vote: I like it +69 Vote: I do not like it

To my disgust, I actually thought those ponies were standing on two of thier legs and I wondered what that third thing was.. figured it out now.

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

    I cant unsee it, it will haunt my dreams forever

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

I now must watch my little pony now to try to get a better score on this contest.

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

Woahh, it's so cute <3

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

NERD_MAX = Helping My Little Ponies on CF.

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

Oh god unfortunately I cannot participate in this My Little Pony round because something has come up. How do I unregister from a contest? I can't find it.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Go to the number of participants link beside the contest and click it. There will be a cross symbol beside your name. Just click on it. Moreover, you can also not submit anything during the contest. It won't affect anything.

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4 years ago, # |
  Vote: I like it +52 Vote: I do not like it

weird flex but ok

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

Never watched My Little Pony animated series but the contest seems interesting!!

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

Behind this cuteness, I believe there will be some dangerous problems. Best wishes to everyone. Go and be high rated ;)

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

    ofc there will be some dangerous problems if problemsetter is severe highschool girl from Chelyabinsk

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

bronies everywhere...XD

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

Will I be able to finally get my colour?

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

wow, a second My Little Pony contest since Codeforces Round 259 (Div. 1)!

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4 years ago, # |
← Rev. 3   Vote: I like it -8 Vote: I do not like it
Expecting a problem statement be like
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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I didn't see Rust in the registration email. Is that a mistake or is Rust really not available for this round ?

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

What are the things hanging between the legs of the ponys'?

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

I didn't know sparkle is one of the main ponies. Thank you for this round, I'll be waiting for some nice puns.

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

Wow!

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

The background looks so...cute?

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4 years ago, # |
  Vote: I like it -13 Vote: I do not like it

BINOD

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4 years ago, # |
  Vote: I like it +34 Vote: I do not like it

Finally... a perfect excuse to join a rated round after nearly two years!

Oh, it's Div. 2 only...

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

As a pony , I'll participate :)

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

when will codeforces support swift language? Sadlly, So many languages have been added to codeforces but not swift. Swift is really a elegent, efficent modern language! Hope administrator support swift someday!

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

    when will codeforces support asm language? Sadlly, So many languages have been added to codeforces but not asm. asm is really a elegent, efficent modern language! Hope administrator support asm someday!

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4 years ago, # |
← Rev. 2   Vote: I like it +35 Vote: I do not like it

Are problems have been prepared on ponygon?

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

Participating in this round while I have an exam tomorrow feels like suiciding

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

My Little Pony animated series ...

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    A lot of thanks broh, now I can waste my next weeks n weeks watching them <3 =D

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

I am scared, I am noob and don't want my ratings to fall now.

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

    Why worry? If ur rating drops, next time it'll be easier to raise them, never worry about that when participating in a contest.

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

Finally scrolling through a comment section where you can actually read the comments.

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

GL HF

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

Hey! Hello? Am I on the blogpost?

Well, guess what?

Yes, I am! And that's Awesome!

Problems setters, Pinkie loves you sooooooo much, too much that I want to throw a party!

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4 years ago, # |
  Vote: I like it +93 Vote: I do not like it

Ready for contest!

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4 years ago, # |
  Vote: I like it +128 Vote: I do not like it

I hate the story of problems! :(

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

    For real...

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    4 years ago, # ^ |
      Vote: I like it +40 Vote: I do not like it

    This endless blah blah apple here flutterapple cakeapple there because fluttepie with cakeflutter there is only annoying. This is no fun.

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

    Yup the cringe level was just off the charts!

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

No offence to problem setters ,but i am unable to understand the question itself.

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4 years ago, # |
  Vote: I like it +21 Vote: I do not like it

wtf the statements say?)

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

Horrible statements. I couldn't even understand what was asked.

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

Can I get my ratings back by nothing playing this round :(

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Yeah!! If you haven't submitted your solution even a single time, then you can leave the contest. There will be no change in your ratings!!

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

Is it an English Comprehension Contest?

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4 years ago, # |
  Vote: I like it +67 Vote: I do not like it

Are we here to code or improve our vocabulary.Seems like its and Mock IELTS/TOEFL Tests.

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

    Even they have to make 2 announcements for writing the correct question!! But till now I am unable to understand what they are trying to convey in the first question.

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

      yea same with me...i cant understand how are the blocks kept..

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      yeah even i guessed about the question and solved according to that

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4 years ago, # |
  Vote: I like it +41 Vote: I do not like it

Poor statements!! I am unable to understand even the first question !!

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

There was no need to have a sooooooo long story, it would be better to have a more mathematical statement than a confusing long story.

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

The names of the characters were so complicated to keep track off and the long stories. Sorry but not a good contest.

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4 years ago, # |
  Vote: I like it +123 Vote: I do not like it

lmao
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    4 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    This isn't meant to offend anybody, I just posted it to make this very clear that problem statement is where one should give more time then framing story. No doubt problem statement could be better

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

This was just waste of time.... The problem statements were so confusing. Actually this contest was not of coding but english.

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

I dont care how pinky pie eats her patty cakes just tell me what I have to code for!

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4 years ago, # |
← Rev. 2   Vote: I like it -16 Vote: I do not like it

I hate the story of problems! :(

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

Not able to understand even first problem!

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4 years ago, # |
  Vote: I like it +54 Vote: I do not like it

The statements should be simple. There is no need to always introduce a story in the problem. I am very disappointed after this contest.

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4 years ago, # |
  Vote: I like it +25 Vote: I do not like it

Why the f*** do I have to see these DISGUSTING PONIES.

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4 years ago, # |
  Vote: I like it +56 Vote: I do not like it

Why the fuck you want to include stories in problems, and these weird names- Rainbow dash, Flutter shy..... What do you think, by including stories, the round becomes interesting??

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4 years ago, # |
  Vote: I like it +59 Vote: I do not like it

no more storyforces

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4 years ago, # |
  Vote: I like it +92 Vote: I do not like it

How did all of the contest setters agreed to release these kind of statements?

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

Too much storytellings... Just give us simple statements please...

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

Contest in a nutshell: Read the stories and fall asleep. Setters be like.. Didn't understand the question? We did not want you to.

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4 years ago, # |
  Vote: I like it +17 Vote: I do not like it

I don't like pony stories anymore.

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

It's really not that hard to write clear, concise statements.

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4 years ago, # |
  Vote: I like it +32 Vote: I do not like it

It took so much time to understand problem A :-(

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

To the guy who designed the problem statements: Hats off! You've a tendency to play around with words and over-complicate easy to understand sentences.

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

I planned to watch My Little Pony when I was reading the announcement, but after this contest, I would say no.

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4 years ago, # |
← Rev. 2   Vote: I like it -23 Vote: I do not like it

How to solve A after the contest?

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

    Do not discuss problems while contest is running.

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

    n/2 + 1

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      How?

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        make an exemple for n=4 and n=5 on the paper.In the first step you can color the "1st layer" (near the border). In the second step the second layer and so on.In the n/2th step you will reach the mid layer (+1 for the center).

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4 years ago, # |
  Vote: I like it +120 Vote: I do not like it

Am I taking an English examination?

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4 years ago, # |
  Vote: I like it +190 Vote: I do not like it

The statements are too long and there are too many unnecessary(as I think) stories.

And there was even a typo in the statement of problem B. As you can see in the picture below, the two phrase "After the sixth event" came out incorrectly as "After the second event"(Only true for the latter). Although the typo was fixed after a while, there wasn't announcement about this. Moreover, I posted the comment similar to this about 1.5h before, but after about an hour, the comment was deleted for an unknown reason.

Why couldn't no one find the typo before the contest? Why there wasn't announcement about the typo? And why my previous comment disappeared? Not pretty good. :(

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

This round tested our English rather than our programming skills.

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

Just asking. Are the top rankers(in this round) even trying problem E1 lol

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4 years ago, # |
← Rev. 2   Vote: I like it +46 Vote: I do not like it

Now I got a reason to hate pony.

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4 years ago, # |
← Rev. 2   Vote: I like it +7 Vote: I do not like it

Was I the only one who found C way easier than B (At least on the implementation side)?

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

    For me the number of unpronounceable word in statements defines the hardness of problem.

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4 years ago, # |
  Vote: I like it +17 Vote: I do not like it

Enough grid construction and heavy weight english word exercise for today. I quit.

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

How to solve D?

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    here

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +44 Vote: I do not like it

    Let $$$dp[i][j]$$$ denote the size of the largest rhombus with the bottom vertex located at $$$(i, j)$$$.

    Suppose the colours at $$$(i, j)$$$, $$$(i - 1, j - 1)$$$, $$$(i - 1, j)$$$ and $$$(i - 1, j + 1)$$$ are all the same, $$$dp[i][j] = min(dp[i - 1][j - 1], dp[i - 1][j], dp[i - 1][j + 1])$$$ + (1 if the vertex opposite to $$$(i, j)$$$ has the same colour as $$$(i, j)$$$)

    If the colours are not the same, $$$dp[i][j] = 1$$$

    Now, just iterate over all bottom vertices $$$(i, j)$$$ and count the number of rhombuses using the dp values.

    Code: https://mirror.codeforces.com/contest/1393/submission/89259501

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

      Wow, never got the idea using 1 dp. I got idea using 4 arrays. up, down, right, left.

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

        Recently watched a video of largest square in grid, and applied the same idea here

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4 years ago, # |
  Vote: I like it +17 Vote: I do not like it

Why the fuck memory limit on D is 256 MB

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    4 years ago, # ^ |
      Vote: I like it +31 Vote: I do not like it

    Because $$$30$$$ MB is enough.

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

      A dp from every corner so 4 matrix of 2000*2000 ? P.S. that s 4*16 mb so nevermind

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I thought 256 MB is a normal memory limit?

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    No clue, but you can code the same solution by just considering for each character one at a time, doesn't change total time complexity anyway if you were planning on storing pref[26][n][m] or something similar.

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

    I agree. That and the tight time limit cost me a good 150 points and 20 minutes and it must have cost others points too. The constraints were way too tight.

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I have O(n * m * k) sol, where k is alphabet, and I'm getting TLE. Perhaps it was supposed to stop rotation or even force O(n * m), but seems v tight for little reason.

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

    I had done using only 2 2D array(one for input and other for DP). So, size is 2*2000*2000*4 bytes = 32MB.

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4 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Can somebody tell me the idea behind problem C? I tried like everything. Thanks in advance!

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

    Apply Binary Search MySolution

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

    the answer will depend on the maximum frequency of a number and count of maximum frequency. To notice that see that if max freq is 3 , it occurs twice , you can make ab...ab...ab , now just from this you can notice that ans would be (n-(mx)-(cnt-1))/(mx-1), as you need cnt — 1 spaces from the end and to populate mx freq you need mx spaces , out of remaining spaces you need to partition it in mx-1 segments like ab...ab...ab , which is optimal when we divide them equally or just division. Link — my solution

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      but why only max frequency is considered?

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

        because numbers having frequency lesser than maximum frequency can always be adjusted in the middle without lessening min distance

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Because for other frequency we can insert them in empty spaces between those of max frequency and they won't come out of the array because they are strictly less than max, for ex — if 3 , 2 ,2 ,1 is freq array and numbers for them is a,b,c,d then there are 3 a's , we want maximize their separation first, so we equidistantly place them , so a...a..a, Now every value has freq<=2, which can be placed in each of empty spaces between these a's, so their min distance won't decreas

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I did the same.

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

      I used binary search to look for the solution. My solution passed the pretests but gave WA on test 43. I don't know where did I go wrong. Link to my solution: https://mirror.codeforces.com/submissions/i_m_eshaan17# Can you please see what thing I missed out

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Wow. Nice Solution.

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

    Look u have to find frequency of the number occuring most number of times. now find total how many numbers are there having this frequency int val=n-maximum_frequency-(count of numbers having maximum frequency -1) val/(maximum_frequency-1) will give the right answer .

    Let us see this with 2 different examples {1,2,3,1,2,5,1,2,8,1} Here the maximum frequency is 4 and the number having this frequency is 1 so we can see answer will be 2 Now lets take change the example a bit {1,2,2,1,2,5,1,2,8,1} Here the maximum frequency is 4 and the numbers having this frequency are 1 and 2 so now you can see the answer becomes 1 {1,2,1,2,5,1,2,8,1,2} can be one solution reason is that 1 has maximum frequency so we arrange array like 1....1....1...1 we put 1 at both ends to maximize the distance and put other elements between 1s but when 2 also has frequency 4, two 2s will start falling between two 1s(something like 1,2,2,1.... So,every time we encounter another number having maximum frequency we need to put it at last (something like {1,2,1,2,5,1,2,8,1,2}) Look at the first test case for a bit of clarification

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

Was it just me or did others find the wording of the first question a bit difficult as well?

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

Today I get to know why we were taught English first then programming.

Though the concept and problem idea is good, I suggest the Problem statements can be used for essay writing competitions.

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

I'm doubting my English skill after this contest

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

I solved C and still can't understand A

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

what is the pretest 5 of problem D?

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Pretest 5 cost me 2 WA, but it was my silly mistakes...

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

    Try this:

    4 5
aaaaa
aaaaa
aaaaa
aaaaa
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      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      The correct answer for that pretest is 26, right?

      Thats what my code is printing as well.

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

        I was able to fix my code for that problem.

        For those wondering, the pretest I used was

        tc

        However I believe maksio's test should provide an error as well. The only change needed is change it to a 5 * 5 matrix of a's

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

    I see you have done DP similar to me too. The issue in your code seems to be that you are wrong in up and down dp.

    You can see my code, bam is similar to left, dan is similar to right, up is dp1, down is dp2.

    Basically, c should be updated as 1+2*min(bam, dan) and and d should be up[i+1][j]+2, not 1.

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4 years ago, # |
  Vote: I like it -18 Vote: I do not like it

Bye Bye rating

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4 years ago, # |
← Rev. 2   Vote: I like it +25 Vote: I do not like it

The problems were good but the wording of problem A messed up my tempo. Also the names of the characters (i assume names of ponies ) confused more from understanding the problem statement. I would recommand using some common and familiar english names.

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4 years ago, # |
← Rev. 8   Vote: I like it -70 Vote: I do not like it

image.jpg

No comment

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +25 Vote: I do not like it

    .

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

      Look she has a rating which is much higher than mine and I am gonna get about +120 after this round but seriously this contest could have been better and what the fuck are you even talking about

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

She confused the contest with the storybook

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

You can choose to become a writer rather than a contest designer

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

What is the correct approach for C??

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    bsearch answer, then for each iteration, always greedily put down the number with the largest remaining frequency that is available.

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Can you please, share your check function?

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        89248346

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

          Where my check may fail

          Spoiler

          89275212

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          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          can you plz plz check this function https://mirror.codeforces.com/contest/1393/submission/89275288

          Spoiler
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          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          can you please explain the logic?

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      no need to use bs :v

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        4 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        i mean sure, but for me it was easy to see a bsearch solution, and it fit in the TL.

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

    My approach:

    Count the frequencies of each unique element.

    Note that if there are multiple most frequent elements, you can discard all but one unique element. If both 1 and 2 appear as frequently as possible, you can just do 1 2 .. 1 2 .. 1 2. This reliably increases the distance between alike elements by 1.

    Note that the optimal arrangement for the most frequent element will always be 1 .. 1 .. 1 where 1 is the most frequent element, and you fill things in the middle.

    All remaining elements can be inserted into the ... spaces in some way (proof is left as an exercise). So we just count the number of how many things there are that aren't the most frequent, and divide by the number of spaces (the ...).

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      What if the input is 112233. Optimum distance is 2 and it is achieved with 123123. But if we start with 1....1, then we can't get distance 2 anymore. The possible ways to fill the middle are 2233, 2323, 2332, 3223, 3232 and 3322, but they all fail.

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

        I mention that in the earlier case -- because they're all the max frequency, we can treat 1 2 3 ... 1 2 3 ... 1 2 3 like 1 ... 1 ... 1 and just add 2 to our final answer.

        You only need to fill things in the middle if their frequency is lower than the maximum, if they are the maximum you can handle them earlier.

        Final answer is the sum of all frequencies $$$< maxfreq$$$, divided by $$$maxfreq - 1$$$, plus the number of unique elements whose frequency is $$$maxfreq$$$, minus $$$1$$$.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Binary search

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4 years ago, # |
← Rev. 7   Vote: I like it +3 Vote: I do not like it

Codeforces be like lets have a new member in the family : PonytaleForces !

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4 years ago, # |
  Vote: I like it +42 Vote: I do not like it

storyforces

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

Lol what the heck was this contest

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

    It was a english grammer contest,this contest increased my english reading skills :XD

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

what's the idea in problem C

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4 years ago, # |
  Vote: I like it -6 Vote: I do not like it

Kindergarten question designer is better for you

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4 years ago, # |
  Vote: I like it +99 Vote: I do not like it

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

I saw this coming thats why I tried confirming it here , looks like they were joking back then.

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

Write stories if you want, but please at least give us formal definitions for the operations to be performed.

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

What is the approach to solve D?

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    for each cell we calculate the number of ways to form a pattern with center is the cell.

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

    $$$up_{i,j}$$$ = Number of cell with same color above this cell
    $$$dn_{i,j}$$$ = Number of cell with same color below this cell
    $$$a_{i,j}$$$ = $$$min(up_{i,j},dn_{i,j})$$$
    $$$b_{i,j}$$$ = max size of left half of a rhombus centered in this cell
    $$$c_{i,j}$$$ = max size of right half of a rhombus centered in this cell
    $$$m_{i,j}$$$ = $$$min(b_{i,j},c_{i,j})$$$ = max size of a rhombus centered in this cell
    $$$ans$$$ = sum of all $$$m_{i,j}$$$

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

    Notice that all squares can be treated as a rhombus of size $$$ 1 $$$ and count them. After that remove all squares that can not be a center of a rhombus of size $$$ 2 $$$ add those left to the total number of rhombuses. Do this again for size $$$ 3 $$$ and so forth.

    How can this be done?

    Notice that a cell can not be the center of a rhombus of size $$$ n $$$ if there exists a cell of a different color such that the Manhattan distance between the two cells is less than $$$ n $$$.

    Using this fact we can implement a multi-source BFS from all cells which have different colored neighbors and in each round count the number of cells that are not visited. (Be aware that the memory and time limits are quite tight).

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Interesting point of view. Is it $$$O(nm)$$$?

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

        Yes, because this solution is almost only BFS and the graph that the BFS is run on contains $$$ nm $$$ nodes and about $$$ 4nm $$$ edges. Therefore the complexity is $$$ O(nm + 4nm) = O(nm) $$$.

        However the constant factors are quite large and I lost a good $$$ 20 $$$ minutes and $$$ 150 $$$ points (due to submissions) trying to optimize them. IMO the limits are way to tough and a solution with the expected complexity should pass immediately.

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

It's a competition where I've got the best result I hope I won't be hacked

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

When will the Editorial be published?

By the way, the contest you prepared was great!

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

My video editorial for Problem A and Problem C

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    why we can not paint 4*4 grid in two step

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Because after two steps not all fields are painted.

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

        why we can not paint cell (1,1),(1,3),(2,2),(2,4),(3,1),(3,3),(4,2) and (4,4) with one color in first step and all remaining cell with other color in second step

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          4 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          We want to have chessboard as result. So first is (1,1),(1,3),(1,5).... on all four sides.

          Second is the fields in between of the ones from first, and every second fields of row/col 2,n-2. And so on.

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

          You can't paint (2,2) in the first step, as it is not neighbouring to the last painted cell, Read the question statement again you missed this point.

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    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    why only the elements with max count are required?

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      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      If you try to spread the elements across the array the ones with max count would end up closest.

      Lets say freq of max element is 5 then u have X__X__X__X__X and u can place all elements of lower freq in different spaces so they will be atleast as far as a pair of X.

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      4 years ago, # ^ |
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      Because we are essentially dividing the array into groups right? So for the element which has max frequency n/(fr[x]) element will be minimum hence the least spacing

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4 years ago, # |
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Where I am wrong in Problem B!, I just counted number of active planks , with updating frequency table for each plank entry as entry and exit happens and also in this frequency table maintaining the maximum value and number of odd and even values, now the answer is YES only when maximum value in frequency table >=4 and also total planks %4==0 and no odd frequency is there in the frequency table else answer is always no.?

Where I am not getting problem statement please tell my mistake!

Thanks in advance.

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    4 years ago, # ^ |
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    You have to make only 2 storage.

    You only need planks (a,a,a,a) and (b,b,c,c). {here a,b,c are sizes of planks}.

    In total you need just 8 planks.

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      4 years ago, # ^ |
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      This is nice explanation. Knowing that the problem statement is understandable, too.

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      4 years ago, # ^ |
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      Thanks I think that I misunderstood the problem as in total we can more than one rectangle and square storages, confused with the word storages in the problem statement. Thus just one change of making count to 8 will make my solution pass, I dont know what is the sense of such problem statements and what they checked. Facepalm after losing 120 Rating again I gave the contest today as my mood was bad and I thought of freshing up my mood but Now I cant describe to what scale the statements worsened my mood again.

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        4 years ago, # ^ |
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        Did you read the announcement? I did exactly the same as you before reading it and it cost me 3 WA's and half an hour. :(

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    4 years ago, # ^ |
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    I didn't do well in this contest but could solve B.

    Here is the way I did it, keep 4 sets (two, four, six, eight) two => freq[2, 4) four => freq[4, 6) six => freq[6, 8) eight => freq[8, inf)

    Now as queries come, these tables can be updated on the fly in somewhat O(logn)

    You can build when

    8 has >0 members (2 squares)

    6 / 4 has >1 members (2 squares)

    6 has >0 members and 4/2 has >0 members (1 square, 1 rectangle)

    4 has >0 members and 2 has >1 members (1 square, 1 rectangle)

    the overall complexity is O(nlogn + qlogn)

    You are basically missing lots of cases and also not all planks are required to be used, so the %4 check is completely incorrect

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

    You can do it with much more simplicity. Just maintain a map to count the frequency of each element. Now take an array of sets with size 2 : set<ll> cnt[2].
    In the 0th position, insert those elements whose freq is >=2
    In the 1st position, insert those elements whose freq is >=4

    Now, for each query do the following:
    If we need to add/remove something, update both frequency map and the array of sets (check the count and see if we need to remove or insert something in O(log N).
    And to get "Yes/No" we have 3 cases :
    1. If cnt[1].size() >=2 -> YES (we have 2 squares feasible)
    2. If cnt[1].size() ==1
    a. If the freq of the element is >=8 -> YES (we have 2 squares feasible)
    b. Otherwise, see if you can construct 1 square and 1 rectangle by checking the size of cnt[0].
    3. The answer is NO.

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    4 years ago, # ^ |
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    if we have 4 planks of length 1 and 2 planks of 2 and 4 planks of size 3. so total no of planks is 10(toatal planks %4!=0) so it will give no according to your code. But ans is yes

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      4 years ago, # ^ |
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      I think I misunderstood it as all planks must be used too bad mood today thanks buddy for figuring it out!

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4 years ago, # |
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I thought C problem was easier as compared to the B problem or did I overcomplicated my problem B solution?

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4 years ago, # |
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Can anyone plz tell me why getting WA on C https://mirror.codeforces.com/contest/1393/submission/89275288
i m using binary search to find the answer in binary search i m putting the no.s with greatest count first then the no.s with smaller count can anyone plz have a look

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4 years ago, # |
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Was there any edge case in B.I tried every possible combination still it gives wrong answer on Pretest 5.

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4 years ago, # |
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Really a lengthy and messy one , please keep to the point questions

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4 years ago, # |
← Rev. 3   Vote: I like it -35 Vote: I do not like it

Can someone please help me to figure out this issue. This was my cf submission 89275621 but in local PC my answer as was different. 

#include <bits/stdc++.h>

using namespace std;

const int N = 100005;
int B[N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    for (int &i : B) i = 0;

    int t, x, n;
    cin >> t;
    for (int i = 0; i < t; i++) {
        cin >> x;
        B[x]++;
    }

    cin >> n;
    while (n--) {
        char c[2];
        cin >> c[0] >> c[1];
        if (c[0] == '+') {
            B[c[1] - '0']++;
        } else {
            B[c[1] - '0']--;
        }

        vector<int> A;
        for (int &i:B) {
            if (i != 0) A.emplace_back(i);
        }

        sort(A.begin(), A.end(), greater<int>());
        bool ok = false;
        if (A[0] >= 8) ok = true;
        else if (A[0] >= 6 && A[1] >= 2) ok = true;
        else if (A[0] >= 4 && A[1] >= 2 && A[2] >= 2) ok = true;
        else if (A[0] >= 4 && A[1] >= 4) ok = true;

        if (ok) cout << "YES\n";
        else cout << "NO\n";

    }

    return 0;
}
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    4 years ago, # ^ |
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    Your go out of bounds on your A vector (you can start with only 1 type of plank).

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4 years ago, # |
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can someone tell what was the pretest 4 in problem B ??

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4 years ago, # |
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why only the no. with max count are required to find ans in C?

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    4 years ago, # ^ |
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    _pastor_

    Hope this helps
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4 years ago, # |
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So it was a right decision to leave the contest after reading the first problem. XD

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4 years ago, # |
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I appreciate the problems, but does anyone find that it was more unnecessary story, and had lots of ambiguity, specially problem B ?

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4 years ago, # |
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Hoping to see Editorial without ponies.

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4 years ago, # |
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Story forced me read the examples and guess the problem.

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4 years ago, # |
← Rev. 2   Vote: I like it +14 Vote: I do not like it
  1. Short and concise problem statements X
  2. NO BACKGROUND STORIES X
  3. Useful samples X
  4. Super interesting problems X Only thing which was there — Ponies Ponies Ponies
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4 years ago, # |
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Problem D is very similar to this 1015E2 - Stars Drawing (Hard Edition)

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    4 years ago, # ^ |
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    I remembered that problem too, and I actually got a WA in contest because I implemented biggest star instead of biggest rhombus :P

    (surprisingly, biggest star passes all sample tests)

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      4 years ago, # ^ |
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      biggest rhombus can be checked using 4 adjacent square values.

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