McDic's blog

By McDic, history, 4 months ago, In English,

안녕하세요, 코드포스! (Hello, Codeforces!)

I'm super happy to introduce you to Codeforces Round #566 (Div. 2), which will take place on Jun/11/2019 16:05 (Moscow time).

The round will be rated for all Division 2 participants, yet any Division 1 participants are welcome to join us out of competition.

You will be given 6 problems and 2 hours to solve them. Score distribution will be announced later.

The listed handles below are contributors. Thank you for all who listed!

This is my first Codeforces contest ever. I hope everyone who will join this contest enjoy. Thank you!

WINNERS:

  1. Castor
  2. thecodinglizard
  3. puyu_liao
  4. UoA_Kanade
  5. It5t
  6. LucaSeri
  7. orz_liuwei
  8. emengdeath
  9. ashutosh450
  10. hyfzbtrs

UPDATES:

  1. Let me spread the meme from McDic Minecraft Telegram group — Ggungah.
  2. Score distribution is 500-750-1250-2000-2250-2750.
  3. Editorial is available.
  4. Congratulations for the winners!
  5. I am sorry for weak systests for B and F. Sorry again.
 
 
 
 
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4 months ago, # |
  Vote: I like it +8 Vote: I do not like it

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

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4 months ago, # |
  Vote: I like it +53 Vote: I do not like it

Best of Luck for your first contest as a problemsetter.

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4 months ago, # |
  Vote: I like it +88 Vote: I do not like it

Wa! A Korean round!

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4 months ago, # |
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upvote if you believe there will be kpop tasks in his korean contest

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    4 months ago, # ^ |
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    that will be wonderful(P.S BTS ARMY)

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    4 months ago, # ^ |
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    Listen to twice while solving twice problems.

    skill 1000

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      4 months ago, # ^ |
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      listen to twice twice while solving twice problems twice.

      skills 1000000007

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4 months ago, # |
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Hit you with that ddu-du ddu-du du~

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4 months ago, # |
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I wish everyone high rating!

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    4 months ago, # ^ |
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    Excellent tester for Excllent Contest ㅇㅅㅇ

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4 months ago, # |
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Korean round will be amazing!!!Oh my my my, oh my my my! I've waited all my life. Oh my my my, oh my my my! Looking for something right:)

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4 months ago, # |
  Vote: I like it +164 Vote: I do not like it

Why Hello is 안녕하세요 but Codeforces is 코드포스 which is shorter than Hello?

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

    Also thought how difficult is it to write just "Hello", just unbelievable

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    4 months ago, # ^ |
      Vote: I like it +58 Vote: I do not like it

    That's not even a Hello.

    It's a Hi. XD!

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      4 months ago, # ^ |
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      The other side is that Hi is longer than Hello! xD

      여보세요 : Hello

      안녕하세요 : Hi

      Google Translate

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        4 months ago, # ^ |
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        And 'Hello' can be used as both '여보세요' and '안녕하셰요' in my country, so It is also able to say the length of 'Hello' and 'Hi' is equal. :)

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        4 months ago, # ^ |
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    4 months ago, # ^ |
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    I have always wondered how Chinese/Korean people write things

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      4 months ago, # ^ |
      Rev. 2   Vote: I like it +34 Vote: I do not like it

      That's an art :D

      (However I have not mastered it yet. T_T)

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      4 months ago, # ^ |
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      It is actually very simple. We have these Oriental supernatural psychic abilities to inscribe complex letters into paper without using hands.

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      4 months ago, # ^ |
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      I wonder how Arabs too

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        4 months ago, # ^ |
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        Nope writing Arabic is easy.Arabic alphabets are simple in shape.

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        4 months ago, # ^ |
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        No, I'm Iranian and our font, Persian or Farsi is like Arabic. I think it is easy. :D

        Maybe these different opinions are because of different viewpoints. For us Korean or Chinese are hard to understand. But now I see that you think Arabic is difficult. Because we all are used to our own languages and other ones seem strange. But the most important think is that all languages are beautiful. :D

        Sorry for my bad English. :D

        Btw do you Korean think your language is hard? Maybe I'm wrong.

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          4 months ago, # ^ |
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          Though I write Chinese since I born, I still think writing it is a exhausting job, lol.

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          4 months ago, # ^ |
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          Korean letter seems scary because one syllable is cracked into a single letter. However, it's actually a composition of consonant letters (ㄱㄴㄷㄹㅁㅂㅅㅇㅈㅊㅋㅍㅌㅎ) and vowel letters (ㅏㅑㅓㅕㅗㅛㅜㅠㅡㅣ). So while there are 11172 Korean letters, you only have to remember 24 simple letters- after then you can write all of them!

          Korean people are proud of their language, and we have a "language day" which recently became a holiday. I also think this unique system makes pronunciation much clearer and complete. However, I'm not sure if it's easy, because "easy language" and "easy letters" are a different matter, and "smart letters" and "easy letters" also are. It's my mother tongue, so at least I'm not the one to judge.

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    4 months ago, # ^ |
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    Technically it's Annyeonghaseyo XD

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    4 months ago, # ^ |
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    let's hope problems statements are long in Korean

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    4 months ago, # ^ |
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    Well, if you use hanja honyong(漢字混用) to write 안녕하세요, the meaning of the phrase would be clearer (especially for Chinese). 안녕하세요=安寧하세요, it's asking if someone is free from worry. And, 코드포스=Kodeuposeu. This word is just a transliteration.

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4 months ago, # |
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Waa~~ It will be Good Good Round~~ :)

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4 months ago, # |
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korean round <3

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4 months ago, # |
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It will be good round :D

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4 months ago, # |
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How does it feel to have div2 after div3?

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4 months ago, # |
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BTS brought me here!!

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4 months ago, # |
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i hope there will be short questions !

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Rev. 2   Vote: I like it -37 Vote: I do not like it
  1. -Is it THE BEST div2 in the world? -No, Codeforves Round #566 Div2 THE BEST
  2. .Or
  3. -Is it THE BEST div2 in the world? -No, Codeforves Round #567 Div2 Was THE BEST
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Rev. 2   Vote: I like it +57 Vote: I do not like it

"...Thank you all who listed!:
- myself, arsijo
- myself
- arisjo
- tester — [some testers and myself]
- Mike"
tm McDic

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4 months ago, # |
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Finally your round has arrived! Congrats! :D

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4 months ago, # |
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The contest has extra-registration?

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4 months ago, # |
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I hope a once wins your round :D

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4 months ago, # |
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Unusual time for the contest, again

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4 months ago, # |
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I wish it will be a great contest . Thanks for this Effort

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

... and who is the mother? did cf and polygon got born by bipartition?

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4 months ago, # |
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Happy ratings to everyone

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4 months ago, # |
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크으.. 국뽕에 취한다.. Cheer up McDic !

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

I want to do last contest as a Specialist. -> Blue

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    4 months ago, # ^ |
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    Focus on the problems and worry less about your ratings, it will automatically follow :)
    All the best!

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    4 months ago, # ^ |
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    Deeply immersed by your curve :D

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      4 months ago, # ^ |
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      Sorry to say, My C failed due to my minor mistake.

      Hurt me a lot.

      I gave too much effort into C.

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      4 months ago, # ^ |
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      I think I will miss by +1 rating for becoming blue.

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4 months ago, # |
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sees a codeforces round
Me: Codeforces round yay!
notices it's korean
Me: Codeuposeu round assa!

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4 months ago, # |
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BTS bring me here

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4 months ago, # |
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Is it rated up to 2100 rating like many other div2 contests?

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Blackpink also cool)

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

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

Maybe the reason for the unusual time of the contest is Iran vs South Korea soccer match! Korean want to watch the match to increase their confidence and rate in a contest. Wish a good game and a good contest too!

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    4 months ago, # ^ |
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    Or maybe Korean football players want to participate in their contest (;

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4 months ago, # |
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Let me fly up to Purple on gookbbong round~~~~~~~~

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4 months ago, # |
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Do you guys think doing a contest after anesthesia is a crazy idea?

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    4 months ago, # ^ |
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    Yes, it is a crazy idea

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      4 months ago, # ^ |
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      Well let's see how much I can get negative rating.

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    4 months ago, # ^ |
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    i think it will be a great idea for me ,i won't feel the pain of my rating not increasing.

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    4 months ago, # ^ |
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    Guys, don't try this or you will end up competing with half-closed eyes xD

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퍼플가게해주세요...(Let me go to Purple this round)

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4 months ago, # |
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Hmm. Why does nowadays always 6 problems? Is this only fast coding?

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https://t.me/mcdic_ch

If anyone needed link to his minecraft telegram channel...

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    4 months ago, # ^ |
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    That channel is not used for a long time.. lol. I have active chat group now.

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      4 months ago, # ^ |
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      That is all what I found, sorry :D

      So share your active chat group!

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It seems that I haven't got the ability to solve problem D as it scored 2000. (smog

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4 months ago, # |
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Seeing the score distribution , i guess it is (speed + implementation) contest.

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hi team :)

is the contest rated for div 3?

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That's why I love $$$ $$$ ̶M̶a̶t̶h̶f̶o̶r̶c̶e̶s Codeforces

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[deleted: irrelevant]

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4 months ago, # |
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4 months ago, # |
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What an amazing implementation contest!

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4 months ago, # |
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In D why answer is not center of tree ?

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    4 months ago, # ^ |
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    check a look:

    4

    1 2

    2 3

    3 4

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    4 months ago, # ^ |
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    Try this case:

    8
    2 1
    1 3
    3 4
    4 5
    1 6
    6 7
    7 8
    

    The only answer is $$$2$$$.

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      4 months ago, # ^ |
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      so if the answer is not the center, then it must be one of the leaves right ? How to check that ?

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        4 months ago, # ^ |
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        Suppose $$$v$$$ is not a center and not a leaf, then there are two leaves $$$l$$$ and $$$m$$$ at different distances from $$$v$$$ (suppose $$$l$$$ is closer). Consider the vertices at the same distance from $$$v$$$ as $$$l$$$ and notice that some of them are not leaves.

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          4 months ago, # ^ |
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          Ok thanks but I know how to prove that. What I want to ask is that if it is not the center, how could we find the leave which is the answer ?

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        4 months ago, # ^ |
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        I tried to find centroid on slightly modified graph(I deleted chains starting from leaf nodes) I was late for about 30 sec to submit

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How to approch E ?

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    4 months ago, # ^ |
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    The powers of f3, f2, f1 were terms of different tribonacci sequences with different first numbers. I couldnt figure out the sequence of powers of c, and it was also not there in OEIS :(

    Matrix Exponentiation is must, but couldnt figure out the matrix for c :'(

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      4 months ago, # ^ |
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      Yeah, same ... wasn't able to figure out powers of c. Didn't know about OEIS though. Thanks for that :D

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        4 months ago, # ^ |
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        If you make $$$n=n-3$$$, then powers of c would be $$$2*\sum_{i=1}^n i = \frac{ n*(n+1) } {2}$$$

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      4 months ago, # ^ |
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      You could reduce the problem to solving $$$G_{x} = G_{x-1}*G_{x-2}*G_{x-3}$$$, if you take $$$G_{x} = c^x F_{x}$$$. But, I couldn't see the fibonacci thing lol. Maybe we should have given the contest together xD.

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      4 months ago, # ^ |
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      Power for c was (n-2)*(n-3) using summation of AP formed: 2*(1+2+....(n-3)).

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    4 months ago, # ^ |
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    The answer is some power of $$$f_1,f_2,f_3,c$$$

    To deal with the power of $$$f_1,f_2,f_3$$$ it is a three-term recursion.(Fibonacci number is a two-term one). It can be rewritten in matrix form, and use fast power for large power.

    To deal with $$$c$$$ it is 2* A062544 in OEIS? It has a closed matrix form and solve it similar to the first one.

    Update 1 : Check tutorial/other stuff for better calculation of c

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    4 months ago, # ^ |
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    Let g(x) = logc(f(x)) and h(x) = g(x) + x.

    The original equation becomes h(x) = h(x-1) + h(x-2) + h(x-3).

    After this, the problem could be solved by matrix power mod.

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      4 months ago, # ^ |
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      exponent " c " can be attached with f(X) to make it g(x) = (c^x)*f(x) ;

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        4 months ago, # ^ |
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        Yes. They look equivalent. I guess I am just not very comfortable with exponents.

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          4 months ago, # ^ |
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          I looked at your code https://codeforces.com/contest/1182/submission/55452776

          However, I was unable to understand the last 3 lines :

          ans = mul(ans, pow_mod(C, (3 * ll(a) + 2 * b + c) % (MOD - 1)));
          n %= (MOD - 1);
          ans = mul(ans, pow_mod(C, (MOD - 2) * n % (MOD - 1)));
          

          It would be great if someone could explain them!

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

            Suppose after solving $$$h_x = h_{x-1} + h_{x-2} + h_{x-3}$$$ we end up with something like: $$$h_n = u\cdot h_3 + v\cdot h_2 + w\cdot h_1$$$.

            Therefore, $$$f_n = f_{3}^{u} \cdot f_2^{v} \cdot f_1^{w} \cdot C^{3u + 2v + w} \cdot C^{-n}$$$

            By Fermat's little theorem, we can take the reminder of the exponents mod $$$(MOD-1)$$$ to simplify the calculation.

            I hope this explains.

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4 months ago, # |
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As expected chinese and korean rounds are tooooo mathematical, btw good problems. how to solve d , e and F >

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4 months ago, # |
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how to solve C ??

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    4 months ago, # ^ |
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    sorting first by the number of vowels, then alphabetically, on the one that ends, and then we create two arrays and run by the sorted, we look at the neighbors, if the letters are 2 words, then we sort again and see if the number of letters is equal, then it is 1 word. sorry, i don't know English very well.

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      4 months ago, # ^ |
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      huh! after implemeting c i went for hacks.. toooo messy .

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4 months ago, # |
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Shitty fast typing contest.

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I think in problem C finding m is enough and printing lyrics just makes problem complicated.

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How to solve E ??

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Any idea about pretest 16 in C? Is this logic wrong: For a given word,check if there is a word with same vowel count and same last vowel. If it isn't there,Try to check if there's something with same vowel count.

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    4 months ago, # ^ |
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    case: 4 a e e u

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      holy crap. i should have run a pass first for finding all pairs with both vowel count and last vowel same,instead of doing both at the same time. changed that and your TC passes. Is this logic right? ^

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4 months ago, # |
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C was devastating :))

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Many submission will fail at problem B, i did 4 hacks and was close to 5th.

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    4 months ago, # ^ |
    Rev. 4   Vote: I like it +4 Vote: I do not like it

    some hacks were

    single dot (.)

    single (*)

    and (*****)

    and

    .*.

    **.

    .*.

    and

    5 10

    ..........

    ..*.......

    .******.*.

    ..*.......

    ..........

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    4 months ago, # ^ |
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    Predicted OMG ^^

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      hahaa.. even i went to hacking after first 3 problems as it was very hard to solved the remaining in remaining time. i did 4 hacks, submitted invalid input for 5th otherwise it would be 5. LOLOL..

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        4 months ago, # ^ |
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        so st completed, so many many FST on B.

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C was tough for my current implementation level but I somehow managed to pass the pretests in the last minute of the contest lol

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

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4 months ago, # |
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4 months ago, # |
Rev. 2   Vote: I like it +81 Vote: I do not like it

A: quite nice

B: cases

C: probably some cases too, didn't think of this task

D: quite an easy idea I think, shitty to implement

E: maths

F: maths

I'm sorry, but I didn't find any of these tasks entartaining, very bad problem set (for me).

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    4 months ago, # ^ |
    Rev. 3   Vote: I like it +6 Vote: I do not like it

    good analysis, though d was good. i think the problems were not learning oriented. I was expecting this, as it has became too common in chinese and korean rounds. even dp problems are like they r picked from some maths olympiad books.

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    4 months ago, # ^ |
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    I think D is so hard (sad)

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      Is a nice problem though. I'm still thinking

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    4 months ago, # ^ |
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    first submit D, then talk! you made 9 attempts for D and still couldn't solve it! still a bad problem set FOR YOU?

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4 months ago, # |
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my code shows this output on C Idk why
2
that first
the this
mcdics about
wow round
edit:never mind stupid erase mistake

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4 months ago, # |
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Thanks for fast editorials

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4 months ago, # |
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Why my solution for C (id:55462095) wasn't judged when I submit at 01:59:45?

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4 months ago, # |
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RIP B

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4 months ago, # |
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B = hackforces

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4 months ago, # |
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4 months ago, # |
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If honestly I don't understand. Pretests must be weak or this was just occasionally? I mean hacks like '.' and '*' and test 23 and so on. I understand that it is my fault but all in all pretests was too weak.

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    4 months ago, # ^ |
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    I asked them in the contest time about test only a * and they answered me its a invalid +, so if you were in doubt about this, you could have asked, even tho the pretest should have this test, I think.

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4 months ago, # |
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How to calculate power of c in question E ?

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    4 months ago, # ^ |
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    I think it is 2^(n-2) -2

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      4 months ago, # ^ |
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      For n=8 I calculated power of c as 60 and 116 for n=9

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    4 months ago, # ^ |
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    According to me power of c was (n-2)*(n-3). I wasn't able to calculate powers of f2,f3 in time.Is power of c correct??

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4 months ago, # |
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What an unbalanced contest. Worst problemsetting ever.

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4 months ago, # |
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4 months ago, # |
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Seems like I have to give 2-3 contests to just come back to my original rating now :(

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4 months ago, # |
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it`s a time to be expert ^^

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4 months ago, # |
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E and F was math problem. I think that F was pretty good, because there isn't many Trigonometry Problems

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4 months ago, # |
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What is the test case 23 in div 2 B . My submission is fail on it test case 23 https://codeforces.com/contest/1182/submission/55452743

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    4 months ago, # ^ |
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    Only one "*"

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      4 months ago, # ^ |
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      There should be atleast" +" symbol it neans all upward down left right and middle should be filled..so how single star??

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        4 months ago, # ^ |
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        A "+" shape is described below:

        A "+" shape has one center nonempty cell. There should be some (at least one) consecutive non-empty cells in each direction (left, right, up, down) from the center. In other words, there should be a ray in each direction. All other cells are empty. Find out if the given picture has single "+" shape.

        This is what a + is, so, it s not obligated to have a + shape in the input, and that is why you have to code to find if there is only one + shape in the input, are you kidding me?

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          4 months ago, # ^ |
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          Alteast one is each side is written...so how single star?

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            4 months ago, # ^ |
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            dude, can you talk private? i wana help you

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            4 months ago, # ^ |
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            ur solution fails in :

            5 10

            ..........

            ..*.......

            .******.*.

            ..*.......

            ..........

            answer should be no

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            4 months ago, # ^ |
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            Even I coded the same logic as you. It will fail this case:-

            5 3

            .*.

            ***

            .*.

            ...

            .*.

            Answer should be NO but your code will print YES

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    4 months ago, # ^ |
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    It is something like that :

    6 5

    .....

    ..*..

    .***.

    ..*..

    .....

    ..*..

    Answer is "NO".

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4 months ago, # |
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Can someone check what's wrong in this solution for C? https://codeforces.com/contest/1182/submission/55451525

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4 months ago, # |
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In problem E, I am facing a doubt: I initially thought that I can condense the problem to the powers of f1,f2 and f3(ignore the c power for now). The powers of f1,f2 and f3 will be the nth, (n-1)th and (n-2)th term of Tribonacci sequence. But the powers will be in form of mod(10e9+7). As we know (a^b)mod M != (a^(b%M))%M ex: a=2,b=5,M=3, how do i effectively get the answer?

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4 months ago, # |
Rev. 2   Vote: I like it +3 Vote: I do not like it

For test case 35 of problem B My compiler gave a 'NO' but codeforces custom invocation is giving 'YES' and I think I handled the case on which it is failing.

here is my submission:

Can someone please tell me why is this happenning?

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

    The problem is in your last two loops, it accesses invalid address
    for(ll j=0; j<=m; j++) ( it should be j<m )

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4 months ago, # |
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Can you check my idea for solving "E"? In my point of View we can calculate degrees of F1, F2, F3, C F1's degree is Fib(n)

F2's degree calculates by: F(1) = 1; F(2) = 2; F(3) = 3; F(n) = F(n — 1) + F(n — 2) + F(n — 3) F2's degree equal to F(n);

F3's degree calculates by: F(1) = 1; F(2) = 2; F(3) = 6; F(n) = F(n — 1) + F(n — 2) + F(n — 3) F3's degree equal to F(n);

C's degree calculates by: F(1) = 2; F(2) = 6; F(3) = 14; F(n) = F(n — 1) + F(n — 2) + F(n — 3) C's degree equal to F(n) + (2 * n — 6)

Is my solution right? I got problem with Fast Computing "Tribonachi's"

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4 months ago, # |
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anyone can help me ? my code in problem B get wrong on test 23 But i test it locally and i get it OK

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    4 months ago, # ^ |
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    With what?

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    4 months ago, # ^ |
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    Test 23 has only one "*", are you outputing "NO"?

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      4 months ago, # ^ |
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      I copy test 23 and run in my code and get "NO"

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    4 months ago, # ^ |
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    case: 5 5

    .......*..*.*.*..*.......

    answer is "NO",but you get "YES".

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      4 months ago, # ^ |
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      5 5 ..... ..*.. ..*.. ..*.. .....

      your test is ? if it is , i test it locally and get it yes

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        4 months ago, # ^ |
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        try this one : ans will be no bt ur sol is giving ys.

        5 10

        ..........

        ..*.......

        .******.*.

        ..*.......

        ..........

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

Congratulation to puyu_liao

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4 months ago, # |
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Make it unrated

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    4 months ago, # ^ |
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    Its impossible. There weren`t any technical problems on CF during the round

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4 months ago, # |
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For E,I have an idea.

It's easy to calculate the power of f1,f2 and f3.I have a way to calculate the power of c easily. The transfer matrix:

0 0 1 0 0

1 0 1 0 0

0 1 1 0 0

0 0 1 1 0

0 0 0 1 1

By using this,we can change [a,b,c,d,e] into [b,c,a+b+c+d,d+e,e]

The formula of the power of c is f[i]=f[i-1]+f[i-2]+f[i-3]+2*i-6

Let a=f[i-2],b=f[i-1],c=f[i],d=2*i-6,e=2

So now we can transfer it.

The initial matrix is [0,0,0,2,2],because f[1]=f1*(c^0),f[2]=f2*(c^0),f[3]=f3*(c^0).

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4 months ago, # |
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It was what I worried about. If my country's users set problems for the first time and there was some factors that can be issue, next time my country's (other) users set second problems, people won't expect much.

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    4 months ago, # ^ |
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    For your information, I am not the first Korean problemsetter.

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      4 months ago, # ^ |
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      I see. Anyway, because it's been a long time since there was Korean problemsetter, more prudence should have been.

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        4 months ago, # ^ |
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        Please don't care much about problemsetter's nationality. There are many good Korean problemsetters and I believe community care enough about them.

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          4 months ago, # ^ |
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          your problem set was nice enough

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            4 months ago, # ^ |
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            I, didn't emphasized the problems' quality. And the quality of these is good. The sad thing is weak pretests.

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    4 months ago, # ^ |
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    ainta and .o. set the best Codeforces Round in the history of Codeforces ever, so it's OK.

    On a serious note, I think the round was nice. B is cool for Div2. D is quite interesting with strong pretests. Difficulty distributions are bit flawed, but it's fine if D/E was swapped, and you can see scoreboards anyway.

    (I actually didn't liked problem F, because one can just copypaste NAIPC 2019 D and play with some stupid binary search. but the model solution was easier, and I think it's not an issue for 99% of participants..)

    In the end, difficulty distributions are not something setter can guess correctly, and interesting problems are much more important. For every CF round, there is someone complaining about pretests and distributions, I just advise to ignore them :)

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      4 months ago, # ^ |
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      I, also want to think that way, but since that contest was over before more than 4 years, and since that there was no contest in which Korean was main problemsetter, for users joined after that contest this was like the first Korean problemset contest. It is also true that there are still many chances.

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4 months ago, # |
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Well balanced problem set, nice.

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4 months ago, # |
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problem c: is it valid? this first wow i .

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4 months ago, # |
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how to sove D?

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4 months ago, # |
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Can anyone provide me a clear explanation on D? I thought many things non of them worked properly/on-time.

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4 months ago, # |
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Guys, what is the time complexity of rating changes calculation? Why does it take so long? Can't wait already =)

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4 months ago, # |
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E can also be solved using Reeds Sloane Algorithm(extension of BM for non-prime modulo). Link

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Test case is weak for problem C, there is no case present in the systests where no. of vowels of a string is more than 100000. I used that number as an array index in some part of my code, got AC even after I miss sized the array.

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    4 months ago, # ^ |
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    Exactly. In my solution too I used an array of 100000 for storing the strings with number of vowels. I was sure that my solution would fail at system testing. I was shocked to see it passing. So yeah, Weak Test Cases For Problem C.

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    4 months ago, # ^ |
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    I'm sorry about issue.

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4 months ago, # |
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Anyone who can take a look at my solution for E? 55469911

I have no clue why it passed on small range input but failed on the bigger ones.

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    4 months ago, # ^ |
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    You should calculate exponent modulo phi(MOD) which is MOD-1 in this case.

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Attention!

Your solution 55457716 for the problem 1182C significantly coincides with solutions Athena_1111/55457716, Anti-Mirzayanov/55458879, gandhipaaji/55458903, shreyanshgeek_unofficial/55458966, Harsh_jiit/55459119, turtle407/55459150, kaptaan/55459742, firefox/55459961, shivansh100/55460142, Izanagi/55460447. Such a coincidence is a clear rules violation. Note that unintentional leakage is also a violation. For example, do not use ideone.com with the default settings (public access to your code). If you have conclusive evidence that a coincidence has occurred due to the use of a common source published before the competition, write a comment to post about the round with all the details. More information can be found at http://codeforces.com/blog/entry/8790. Such violation of the rules may be the reason for blocking your account or other penalties. In case of repeated violations, your account may be blocked.

I just got this message. I want to clarify (especially for people who are not aware of that) that I was using the online compiler ideone.com (I was using it for the past 3 contests and nothing wrong had happened before) without knowing that apparently my code was public (I didn't even know that this feature exists). I have not copied the code of anyone!! You can check the timing ( MY SOLUTION WAS SUBMITTED FIRST & I AM 100% SURE AND RESPONSIBLE FOR MY WORDS). I have written every line of this code!!! I haven’t even used functions from any website. It really pains to receive this message in the first contest where I do well. What a luck!!!!!!! :/ Be just.

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    4 months ago, # ^ |
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    "I was using it for past 3 contests and nothing wrong had happened before"

    Good that it happened to you now. Now you will never use ideone.

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      4 months ago, # ^ |
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      It is fine to use it if you have private mode enabled.

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      Why aren't earliest submissions only accepted in case of plagiarism?

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        Because someone can copy the code from ideone and submit it faster than the original author.

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      True, I should've payed attention but it's unfair to be punished because of others' malevolence.

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        4 months ago, # ^ |
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        The world is not fair.You may as well get used to it.

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        4 months ago, # ^ |
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        You are getting punished for your carelessness as well.

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4 months ago, # |
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Why was I skipped in Codeforces Round #566 (Div. 2), but counted rating.

HELP!HELP!HELP!

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4 months ago, # |
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I wonder if there's a solution for D using tree hashing, which I tried but failed.

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shit. load shedding caused my specialist dream.

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Really good and imaginative problems!

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4 months ago, # |
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stupid Solution for D:

There are two possible types of vertexes, corresponds with the statements of the task:
1. One of the leaves
2. Vertex in the "middle" of the tree.

If there is only 2 vertex -> answer 1
If there is only 2 leaves -> answer is one of them

First of all, let's run bfs from each of leaves, and mark all the vertexes with their depths.
(depth[leaf] = 0, depth["middle"] is the maximum). Now, if vertex with maximum depth is unique, lets check it.
After, we need find one vertex with degree greater then 2 (it is always exist because of quantity of the leaves). Run bfs2 from it.
////Let's define nearest vertex with degree greater then 2 for current vertex like a good.
In this bfs, we need mark all vertexes by the pairs = {distance(current vertex, good vertex), index of the good vertex}.
It easy to proof, that if answer is possible, than there is only one leaf with unique pair {distance to its good vertex, quantity of leaves that correspond for this good vertex}. Now we just need to check this leaf.
code: 55487910

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4 months ago, # |
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Why is my code for E giving wa on test case 5?

Got the error ignore.

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4 months ago, # |
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weak tests for D
test
9
1 2
2 3
3 4
4 5
2 6
4 7
3 8
8 9
answer should be 9
https://codeforces.com/contest/1182/submission/55494688 gets AC but it shows -1 for this case.

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    4 months ago, # ^ |
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    OMG I am really sorry about that. I handled almost ten type of trees and it was not enough.. :(

    UPDATE: Added that test in data

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    4 months ago, # ^ |
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    I added that data and rejudged your case. I will try to find the way to rejudge all other's unofficial submissions. Thank you.

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4 months ago, # |
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Regarding question C during the contest I submitted first one Then I found a small mistake and changed it to second one. If you compare both submissions the change was a variable n for a constant value. It was accepted, but then just out of curiousity I resubmitted my first submission third one you can compare it with my first one and it is literally the same, and I got AC with this.

However this is clearly wrong I mean you can test it with a small case ( 4 aaaaa aaaaa aaaaa aaaaa) My first and third submissions return 0 which is wrong and my second one returned 1 which is correct. So I'm not complaining about the fact that I lost points by fixing something that was wrong but would have been accepted anyways, I'm just wondering maybe the test cases are really weak or not good enough.

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    4 months ago, # ^ |
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    I am so sorry about it. I should try so many various selections...

    UPDATE: Added that test in data

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4 months ago, # |
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Let's try our best!