tourist's blog

By tourist, history, 4 months ago, translation, In English,

Hello 2018!

If you're still thinking what to do on the eighth day of year 2018, pay attention! The first round for both divisions of the new year starts on January 8 at 17:35 Moscow time (what about other timezones?).

Four important components of Hello 2018 will be the same as in Good Bye 2017:

  • Div1 + Div2 combined
  • 8 problems
  • 2 hours 30 minutes
  • Rated

But there will also be a substantial difference:

  • Different problems

The problems of this round have been proposed and prepared by YakutovDmitriy, BudAlNik and myself.

Thanks to everyone without whom this round wouldn't be possible as well: AlexFetisov, Golovanov399, KAN, MikeMirzayanov, PavelKunyavskiy, qwerty787788, VArtem, winger.

Good luck!

Scoring distribution: 500 — 750 — 1000 — 1250 — 1750 — 2250 — 3000 — 3500.

Problem tutorial can be found here.

Congratulations to the winners!

  1. Um_nik
  2. desert97
  3. yosupo
  4. dotorya
  5. zeliboba
  6. FizzyDavid
  7. Endagorion
  8. .0.
  9. SpyCheese
  10. Kostroma
Announcement of Hello 2018
 
 
 
 
  • Vote: I like it  
  • +2848
  • Vote: I do not like it  

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4 months ago, # |
  Vote: I like it +175 Vote: I do not like it

The difference is pretty substantial and unique.

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

How sweet we have tourist as a contest writer. Looking forward to the contest.

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    4 months ago, # ^ |
      Vote: I like it -66 Vote: I do not like it

    Yeah thanks to him we have the first hello contest of the whole time

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4 months ago, # |
  Vote: I like it +260 Vote: I do not like it

Now I have a legitimate reason to skip school.

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4 months ago, # |
  Vote: I like it +409 Vote: I do not like it

Wow, wasn't expecting a round with different problems, you guys are full of surprises!

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4 months ago, # |
Rev. 3   Vote: I like it +50 Vote: I do not like it

i can see contestRegistrants in Hello 2018 > Goodbye 2017

UPD: and most of them will be Legendary grandmaster

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4 months ago, # |
  Vote: I like it -119 Vote: I do not like it

i hope that there will be no math problem ...

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4 months ago, # |
  Vote: I like it +543 Vote: I do not like it

And Thanked Mike :D

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

WoW , Contest writer tourist , eagerly waiting for the contest.

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

Registration goal-10k :-)

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4 months ago, # |
  Vote: I like it +590 Vote: I do not like it

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4 months ago, # |
  Vote: I like it +106 Vote: I do not like it

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4 months ago, # |
  Vote: I like it +55 Vote: I do not like it

But there will also be a substantial difference:

Different problems

Best announcement <3

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

    I'm not sure I understand this statement.

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

      He said "Four important components of Hello 2018 will be the same as in Good Bye 2017: ..." before this.

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        4 months ago, # ^ |
        Rev. 2   Vote: I like it -8 Vote: I do not like it

        In my case, I was seeing "Other problems" instead of "Different problems", and I thought he meant 8 problems + other problems. But then it's no longer 8 problems :p But then they fixed it. Not sure why I saw "other problems"

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

      But there will also be a substantial difference:

      Different problems

      Different writers!

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    4 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Also usefull
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4 months ago, # |
  Vote: I like it +21 Vote: I do not like it

Is this the first Hello contest ever made?

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

    yes

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

    No, in 2015 there was such contest. It was put into gym and was unrated, but there was an announcement and countdown to it on homepage etc. http://codeforces.com/gym/100570

    EDIT: Oh, actually it was already mentioned below, I have not seen it before posting it.

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

Best announcement ever!!

Don't miss the chance to hack legendary grandmasters (reals and fakes) :D

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4 months ago, # |
Rev. 2   Vote: I like it -99 Vote: I do not like it

.

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

Nice, one of my biggest competitors setting the problems this time, gonna be fun mate!

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4 months ago, # |
Rev. 2   Vote: I like it -51 Vote: I do not like it

Highest ranked person on CF will not be able to participate

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

So, round by tourist for both divisions and without any purple guys as problemsetters... Seems to be my very chance to stop performing THAT shitty on contests.

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4 months ago, # |
Rev. 2   Vote: I like it -208 Vote: I do not like it

Неплохое начало нового года!)

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4 months ago, # |
  Vote: I like it +64 Vote: I do not like it

Let's not forget the idea of the first Hello contest was from the Sith

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

I'm really waiting about this contest. I hope that will be a good contest for us.

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4 months ago, # |
  Vote: I like it -51 Vote: I do not like it

3.14-rated

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4 months ago, # |
  Vote: I like it -26 Vote: I do not like it

It's going to be a perfect Hello 2018 :)

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

Tourist is going to be first contributor by the end of the contest!

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

Hello 2018.

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4 months ago, # |
  Vote: I like it +18 Vote: I do not like it

This time I don't even have to bet for 10K+ registrants, so I bet for tourist becoming Top contributor! :v

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

*short sad story ...

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

    He still has a shot at solving C

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

Tourist is so overrated. He says anything and people will upvote him

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

    Metsuka is so underrated. He says anything and people will downvote him :(

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

Short statements please!!!

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

I hope know who of the setters did every problem, at least at the end of the competition, but I really want to know during the real competition. Is like knowing who you are facing when you solve the problem.

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

I can't wait to see these problems.

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

Logic Codeforces: participated in previous contest on 5/1/2018 and then the 8/1 is Hello 2018 ?? :D ??

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    4 months ago, # ^ |
      Vote: I like it -31 Vote: I do not like it

    We are pupil so we don't have right to express our opinion, or else we will be downvoted!

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

      nahh nevermind, just speak up what you think tho, as long as they are not offensive

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

      you get downvoted because you are rude and cancerous, I doubt most people have so much free time to click into your profile to know that you are pupil before downvoting

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    4 months ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    maybe the logic is 2018 is 8th year in this decade, so hello 2018 on 8th day of this year?

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

    The other contest wasn't for both divisions

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

well it seems , the contest has legitimate reasons to cross 10k registrants.#Tourist.

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4 months ago, # |
Rev. 7   Vote: I like it +27 Vote: I do not like it
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4 months ago, # |
  Vote: I like it -22 Vote: I do not like it

Finally a round that tourist can't take the first place :D

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

Can any body tell me if i should sleep to prepair for the next day's exam or ... well forget it!

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

Now I wish I hadn't registered for a word games contest in my college. This will be sadly missed :(

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

    This will be sadly missed

    You mean the word games contest right?

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

Not sure if I should rejoice that tourist is the round writer .. or wish my rating good bye

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

With 1100+ uvotes on this announcement , tourist gonna top 2nd leaderboard too.:)

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4 months ago, # |
  Vote: I like it +90 Vote: I do not like it

chinese boy again changed his handle OO0OOO00O0OOO0O00OOO0OO

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    4 months ago, # ^ |
      Vote: I like it +80 Vote: I do not like it

    GG...now the size of this table should be increased to fit in the page.

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      4 months ago, # ^ |
        Vote: I like it +95 Vote: I do not like it

      Or 10 other people should try hard to keep him out of the table.

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

      That's the most unsatisfying thing I've seen today

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

      Or just trim the display after 16 chars

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4 months ago, # |
  Vote: I like it -31 Vote: I do not like it

I dont knoy inglish( I cant anderstend yu(((

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

up to 10K

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

can you please tell me , what does it mean by "different problems" ?? i think every problem is different , from different tags like number theory , graph , dp , dfs/bfs , dsu , data structures ,ad hoc etc .

but i can't understand why "Different problems" is specialized in the blog , can anyone explain ???

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

Yea, eighth day of 2018 is great time to finish new year's eve parties and write some contest :3 But please, could somebody remind me, why is tourist organizing another contest and I still haven't do anything to have my own one?

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

    Oh, yea, I remember now, I'm so lazy, that's te reason... So hoping to see great tasks from you :D

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

      Let's see if you can get upvotes by changing your color to nutella.

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        4 months ago, # ^ |
        Rev. 2   Vote: I like it +36 Vote: I do not like it

        Yea, I've just noticed it... Really, all the time I'm getting upvotes only because of nutella? ;_; I now feel upset, so much racism on codeforces :/ And on the other hand, seriously, no one recognizes me? So much effort, so much tiring and no one recognizes Radewoosh...?

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

          Life of !reds is like this

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

          Well, I recognize you..(yo mama's nephew or best friend)

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

          I recognize you Mateusz!!
          But not just because of your efforts and nutella, we were sitting next to each other at IOI! :))

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

          Dude i do. You were like a star when became nutella. With to 1 places in a row. That was really cool! What was the judge you mainly worked on?

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

          Make Radewoosh Great Again!

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

          Would you yield me an autograph if I say I do? :D
          (you won my contest if anything xD)

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          4 months ago, # ^ |
            Vote: I like it +89 Vote: I do not like it

          pfff people recognize swistakk, not you

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            3 months ago, # ^ |
              Vote: I like it +18 Vote: I do not like it

            Are you trying to start a civil war in Poland?

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

          I also recognize you Mateusz!!! (^o^)/

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        3 months ago, # ^ |
          Vote: I like it +10 Vote: I do not like it

        Holy crap it worked

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    4 months ago, # ^ |
      Vote: I like it -17 Vote: I do not like it

    Because you are still expert :V

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

username should have a valid length. This is totally embarrassing

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

    It's palindrome though!

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

    It looks like a reflection, if you look carefully it's like water moving. :D

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

    This is clearly a sound wave with compressions and rarefactions

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    4 months ago, # ^ |
      Vote: I like it +36 Vote: I do not like it

    He Should Got HANDLE_LIMIT_EXCEEDED

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

      He successfully hacked codeforces design

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

is it rated?? please don't downvote today is my birthday.

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    4 months ago, # ^ |
    Rev. 2   Vote: I like it +19 Vote: I do not like it

    Let's see if this innovative strategy works

    P.S Please don't downvote today is my birthday

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

      thanks for the popcorn mate meet you @ the party

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    3 months ago, # ^ |
      Vote: I like it +56 Vote: I do not like it

    Can't wait for tommorow so I can downvote you

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    3 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Happy birthday ,aha

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

Good Time! I don't have to skip class that day. Excited.

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

Before the contest ... tourist will be the first on the Top contributors list :)

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4 months ago, # |
  Vote: I like it -46 Vote: I do not like it

Codeforces...you are supposed to remove Christmas decorations before January 5th...it is bad luck to keep them up longer than that. I suggest you alter the logo back although I don't know if it's binary or gets worse the longer you leave it, damage may already have been done

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

Dang!

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

Love that Codeforces does new things.

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4 months ago, # |
  Vote: I like it +18 Vote: I do not like it

The comment is hidden because of too negative feedback, click here to view it

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

I hope that OO0OOO00O0OOO0O00OOO0OO will be the winner of the contest.

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

I am so shocked that no one has asked it, Is it rated though?

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3 months ago, # |
  Vote: I like it +102 Vote: I do not like it

Mike did it :D

The Art of Errors Handling...

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    3 months ago, # ^ |
    Rev. 3   Vote: I like it -9 Vote: I do not like it

    And the first character isn't black!

    UPD: eh, sorry for the comment, it's him trying Grandmaster.

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      3 months ago, # ^ |
        Vote: I like it -83 Vote: I do not like it

      He plays with the handle and colors like a kid !

      it was bad behavior to change the handle in such way just to ruin the CF page design !

      such a RED Coder must be more wise and contribute to make this place better.

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        3 months ago, # ^ |
          Vote: I like it -27 Vote: I do not like it

        Very true! Very wise!

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        3 months ago, # ^ |
          Vote: I like it +78 Vote: I do not like it

        He actually contributed in making the place better by making Mike add the handling for long handles :)

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

That moment when I see Div-1 Coder's code failed on system test and my code get AC on same problem :D

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    3 months ago, # ^ |
      Vote: I like it +30 Vote: I do not like it

    The moment i see U talking about Div1 Coders and you are PURPLE :D

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

      it's all about New Year magic :)

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      3 months ago, # ^ |
        Vote: I like it +12 Vote: I do not like it

      Why are you commenting everywhere? -_-

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        3 months ago, # ^ |
          Vote: I like it -7 Vote: I do not like it

        For Contribution I guess :p

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

        You Created a new a count just to ask this question ! :/

        ياض يا قليل :D

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3 months ago, # |
  Vote: I like it -19 Vote: I do not like it

So,say "Hello" to Codeforces with "Hello2018" contest :)

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3 months ago, # |
Rev. 2   Vote: I like it -15 Vote: I do not like it

Look at the Top Contributors list. Only Two more then Top Rating and Top Contributor tourist Love You :). You Are my first crush <3

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Looking at the large number of upvotes for this blog post, I can't wait to see number of registrants exceed 10000

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3 months ago, # |
  Vote: I like it +97 Vote: I do not like it

Can you consider:

  1. Making drain lower?

  2. Turning "handle magic" off for the contest?

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3 months ago, # |
  Vote: I like it -14 Vote: I do not like it

please dont hurt me with hardy problems daddy:(

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3 months ago, # |
Rev. 2   Vote: I like it -15 Vote: I do not like it

tourist Hey Bro :) If you reply me I will show this to my school mates

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3 months ago, # |
  Vote: I like it +109 Vote: I do not like it

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

    Ugh. Sniping the typography nerds with that kerning.

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3 months ago, # |
Rev. 2   Vote: I like it +6 Vote: I do not like it

World War 4 in next few minutes

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

tourist finelly get the first place of the Top contributors :D

well done

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

Lovely scoring distribution

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    3 months ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    but I think problems will not be that easy

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

Hope, codeforces server work fine during the contest.

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

10 min delay

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

We have less than one minute so good luck to everyone!

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3 months ago, # |
  Vote: I like it +8 Vote: I do not like it

Yeah Sure , Let's wait for 10k participants!!

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3 months ago, # |
  Vote: I like it +16 Vote: I do not like it

It seems that we have more 10 mins to prepare the contest :)

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3 months ago, # |
  Vote: I like it +6 Vote: I do not like it

Anyone facing this? HAHA

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3 months ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

9K participants, yeeeeee

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3 months ago, # |
Rev. 2   Vote: I like it -10 Vote: I do not like it

They are waiting for the total number of registrations to get 10000. Very greedy

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3 months ago, # |
  Vote: I like it +156 Vote: I do not like it

Tourist can never create a complete problemset on his own, because he can't tell the difference between div2A-D

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

    uh no he can, that's what a god-like problem-setter does.

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

      He's a god-like problem-solver.

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3 months ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

Wow. More than 9K registrants.

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3 months ago, # |
  Vote: I like it +6 Vote: I do not like it

Extra 10 minutes for 10k registrants :)

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

my first contest of 2k18 ..very excited !!

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3 months ago, # |
Rev. 2   Vote: I like it -8 Vote: I do not like it

codeforces hacking system is such a disaster now!

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Dear Admin , Please make sure that system testing is fast today unlike GoodBye Contest. :)

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

for A, is it possible to hack solutions of this form: cout << m % (1 << n); ??

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Is D ternary search on k?

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    3 months ago, # ^ |
      Vote: I like it +21 Vote: I do not like it

    binary search on k

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      3 months ago, # ^ |
      Rev. 2   Vote: I like it -6 Vote: I do not like it

      When k is small, we have many options to choose from. So just greedily choose the least time consuming problems from sorted vector(acc. to 'a'). This gives a situation where every problem we pick contributes to score. But as k is small, this score is low.

      When k is large, we don't have many options to choose from. So, we have many questions we can attempt, but not all of them might contribute to score, either due to not enough options with a value greater than k, or due to time.

      So, on both sides of optimal k, we get lower scores.

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

        Nope. Doesnt make sense at all. Its clearly binary search.

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

      I somehow got WA with that.

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3 months ago, # |
Rev. 4   Vote: I like it +15 Vote: I do not like it

When you try to be newbie and fool the predictor:

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3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Very clear problem, but so hard to me. Thank you

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3 months ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

Was the hack 30 100000000 invalid for problem A?

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    3 months ago, # ^ |
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    I don't know how A was passing this test case.. I too tried to hack with similar test but failed which resulted in demotivation and regret of why the fuck I tried to hack and now I am going to be ripped off dark blue.

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    3 months ago, # ^ |
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    Maybe you are missing the endline between 30 and 100000000

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      3 months ago, # ^ |
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      I tried again with 30 (and in the next line)100000000 but it showed "ignored".

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3 months ago, # |
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I couldn't get my code to compile, since apparently __int128's don't exist on CF?

http://codeforces.com/contest/913/submission/34030034

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3 months ago, # |
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What is the 6th test in C?

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3 months ago, # |
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Please can anyone tell approach for 'C'?

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    3 months ago, # ^ |
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    If cost[i] < cost[i-1], we can just take 2^i objects instead of 2^(i-1). Just find the answer from binary representation of L.

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3 months ago, # |
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Problem D seemed really fascinating but couldn't really think how to approach it !! Anyone who solved, can explain the idea behind it?

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    3 months ago, # ^ |
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    binary search on k

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      3 months ago, # ^ |
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      That's Nlog^2 right? I thought that it is possible to have a gap in ks, but it wasn't true so I missed this solution. But I wanted to make sure that I haven't missed a more efficient solution (mine is NlogN, but the difference shouldn't matter)

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        3 months ago, # ^ |
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        No, its NlogN. You can sort array t before binary search, and then you simply need one traversal inside binary search. But, you need to keep arrays a and t together, i mean, sorting array t will mix indexes, but you can keep vector of pairs or something to keep a_i and t_i together always.

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          3 months ago, # ^ |
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          Ohh shit, you're right. And it was much easier to code.

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

    I think binary search, actually im pretty sure. First, sort t_i but keep a_i with them ( you can make vector of pairs). You binary search for res, and you go through array a and ask if a_i is bigger than res, if yes add t_i to sum. If you can add exactly res elements so that sum is less or equal to T, then just lo = mid + 1, othervise hi = mid- 1.

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      3 months ago, # ^ |
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      Shouldn't you check if a_i is >= res and not bigger than res. I used the first one and got WA.

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    3 months ago, # ^ |
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    We want to maintain multiset of times for value K when we do a cycle for k from n to 0. Just add all problems with a=k and check if first k elements sum of the set is <=T.

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    3 months ago, # ^ |
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    I've done ternary search by the a[i] ( the min value of a[i] that will appear in the answer ). I was late to submit. So, maybe someone did it with the same approach?

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    3 months ago, # ^ |
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    I did not use binary search or ternary search. I tried all possible answers in decreasing order maintaining the best set of problems so far, in such a way that each problem is added and removed from the set at most once. So it works in : solution.

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3 months ago, # |
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Problem D is binary search, I didnt have time to submit solution, I was late for few seconds literally..

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    3 months ago, # ^ |
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    Mate! Just the same. Understand your feelings :(

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3 months ago, # |
  Vote: I like it +185 Vote: I do not like it

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3 months ago, # |
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I hope there is an elegant solution for problem E. It would be an implementation hell otherwise.

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    3 months ago, # ^ |
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    you need to think in terms of graphs and do some sort of shortest path algorithm which obeys given grammar

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      3 months ago, # ^ |
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      What about the lexicographical thing?

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        3 months ago, # ^ |
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        Will the simplest brute force work? Just iterate through all the possibilities of the combination of logic...It is not that slow I think.

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          3 months ago, # ^ |
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          I thought it work at first, but turned out that some of the answer is really long (more than 12 character), so brute force didn't work.

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            3 months ago, # ^ |
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            So I mean the brute force with minimal branch-cutting. The point is that the brute force must be implemented correctly.

            And yes I think it is hard to debug because some of the expressions are really weird.

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          3 months ago, # ^ |
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          I did that and since possiblities are just 256.I hardcoded them

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            3 months ago, # ^ |
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            I saw your solution. How did you come up with the wierd formulas?

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        3 months ago, # ^ |
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        here is distance is the string and we can write comparator for that as required.

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    3 months ago, # ^ |
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    The implementation is not that bad. Just follow the grammar. The problem, though, it's one of the biggest piles of shit I have ever seen

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    3 months ago, # ^ |
    Rev. 3   Vote: I like it +23 Vote: I do not like it
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3 months ago, # |
Rev. 2   Vote: I like it +2 Vote: I do not like it

 How can someone take n-1 integers as input using this loop and get pretest passed in problem B ?? Or am I missing something ??!!

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    3 months ago, # ^ |
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    It is given that vertex 1 is the root!

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      3 months ago, # ^ |
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      Looks like you didn't get my point. After n, there are n-1 inputs in the problem. But, this man loops from o to n-1, that means he takes n integers. How did he even get output ??!!

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        3 months ago, # ^ |
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        There is input stream closing. When stdin closes scanf doesn't wait for input, it just returns 0. Question is what is u. I don't know, but i presume, that u is dublicate from previous iteration.

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3 months ago, # |
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Shitty Bug ! Spent 1 and half hour on a stupid bug!

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3 months ago, # |
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Really elegant contest with clear statements. Thank you.

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3 months ago, # |
Rev. 3   Vote: I like it +10 Vote: I do not like it

I'm sure that this:

cin >> n >> m;
cout << m % (pow(2, n)) << endl;

Passes system tests, in div2 A.

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3 months ago, # |
  Vote: I like it +51 Vote: I do not like it

You know that sweet feeling when you've been debugging a source that is correct because it fails the example because the modulo is not the standard 1e9 + 7? Well now I do and it hurts like shit especially when I solved the problem 20 minutes before the end of the competition and I just found the bug...Anyway, apart from my mistakes, E was a total shit and I regret that I upvoted the contest

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3 months ago, # |
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matthew99 finally makes a comeback. Congratulations !

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3 months ago, # |
  Vote: I like it +96 Vote: I do not like it

CF's hack system is a total disaster. It should be disabled IMMEDIATELY until admin replaces it's flash-based hack interface

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3 months ago, # |
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Similar problem E link only output length.

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3 months ago, # |
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When you realize after contest that in D it's a[i]<=m to count instead of a[i]>=m. -_- fml fmr(rating)

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3 months ago, # |
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what was the hacks for A and B ?

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3 months ago, # |
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It's true that Problem D is the final "Too Easy Problems" ? :) But anyway, nice contest and nice problems.

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3 months ago, # |
Rev. 2   Vote: I like it +6 Vote: I do not like it

On problem A --> How on earth this --> 34020785 submission passed the inputs test 1:

1000000

1000000

test 2:

12123

12123

test 3:

123213

123213

Can anybody explain??

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    3 months ago, # ^ |
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    Even I got an unsuccessful hack attempt on a similar solution. What I observed was that the value of s becomes some large negative (something like -9.XXXX * 10^9) and the modulo returns the correct, positive remainder.

    Although unsuccessful hack, I am impressed by the cleverness of those guys. I mean, cmon! The hackbait was TOO DAMN TEMPTING XD

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      3 months ago, # ^ |
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      The problem setter is tourist. Can you imagine he haven't noticed that some Contestant will submit this type of solution and those who will try to hack this type of solution will get unsuccessful hacking attempt.Of course he did and that is why he is tourist. And thats how he can fool hackers

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    3 months ago, # ^ |
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    In C++ standard reference casting from double/float to int has undefined behavior if the result lies outside the range of representable values. In VC and G++ compilers it returns MAX_INT for overflowing and the modular works well.

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I failed to hack lots of problem A solutions because of casting from double(in pow method) to int returned MAX_INT and the modular operator returns correct answer. (However in C++ reference, it talks about undefined behavior for overflowing). Anyway I learnt something new :-)

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Ah...give me 10 more mins I can submit E...so sad.

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In Problem A, will the code using power function for all n can get Accepted and if not can anyone help me with the hacks that can be used or if the answer is yes then why is it so because there will be overflow. (sorry about bad English.) Thanks.

// C++ ll is long long

ll solve(ll n,ll m){ ll x = pow(2,n); return m%x; }

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    3 months ago, # ^ |
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    Seems like casting double to int with overflowing surprisingly gives -2^31 as an answer. int(pow(2, 1000)) = -2147483648. And yes, because m <= 10^8, m % (-2147483648) = m (which won't not be true for m > 2^30 or something).

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      3 months ago, # ^ |
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      m%INT_MIN=m is true for all 32 bit signed integers except m=INT_MIN. The reason is the way % operator is defined. a%b+(a/b)*b=a always holds true, and for b=INT_MIN, a≠INT_MIN, a/b when casted to int (rounded towards 0) returns 0. Thus, a%b=a follows.

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3 months ago, # |
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Problem E of this contest is almost the same as today's Problem E.It makes me feel not so good that I struggled on E for about 1 hour only to give up and was told there was a similar problem on Codeforces just after the contest. Link

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

Does the following work on H? I didn't have time to write it due to having too many bugs on G.

Say the x1, x2, ..., xn split [0, 1] into n + 1 intervals: I1, I2, ..., In + 1. Now we do dp, with the observation that the answer on each interval is going to be a polynomial. The dp formula directly shows this. The rest is then just implementing some integrals to compute the density on a real number x after k steps.

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3 months ago, # |
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E is totally same with http://codeforces.com/gym/100867 problem E I don't think it's good.

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3 months ago, # |
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can anyone please explain the approach for C?

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3 months ago, # |
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Anyone have a list of their solutions for all 256 functions in problem E? I can't figure out why I got WA, here's my list: https://pastebin.com/r6Curstb

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3 months ago, # |
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Why does my ternary search logic fail?

When k is small, we have many options to choose from. So just greedily choose the least time consuming problems from sorted vector(acc. to 'a'). This gives a situation where every problem we pick contributes to score. But as k is small, this score is low.

When k is large, we don't have many options to choose from. So, we have many questions we can attempt, but not all of them might contribute to score, either due to not enough options with a value greater than k, or due to time.

So, on both sides of optimal k, we get lower scores.

Edit : The test case I failed was due to > instead >=

But, as others did it with binary search, I wonder where my ternary search logic has flaws.

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3 months ago, # |
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I created (and solved?) a harder version of problem D as I misread the problem statement as:
A task will be taken into account to the final score if a[i] <= total_solved_task. (Indeed, I pass all the samples with this interpretation)

And I wasted more than 100 minutes on it while 1k more contestants solved it :)

It's time to become a Candidate Master :)

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3 months ago, # |
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In hello 2018 round I wrote my submission to problem-C Party Lemonade, it ran well on geeksforgeeks c++14 compiler giving correct ans for test case 4 but the same code with same input gave wrong ans on codeforces c++14 compiler. why is it so.. mysubmission url:-http://codeforces.com/submissions/tibialAcorn98 submission no -34026659

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In problem G, I add some last digits such that the result number N satisfies N % 2|N| = 0 and N doesn't end with 0 or 5. The rest is to find k such that N ≡ 2k modulo 5|N|. It seems to be done by induction.

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    3 months ago, # ^ |
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    I thought the same thing but forgot that N % 2^|N| needs to be 0. If you can prove the minimum |N| needed, there's a way to find k in O(5^(|N|/2) * log(|N|)). Also, it looks like 2^i passes through all numbers not divisible by 5 on modulo 5^|N|. The way to find k is finding the numbers 5^(i * floor(sqrt(n))) and starting from the number you want going back (multiplying by floor(5^|N| / 2) + 1 that's the modular inverse of 2) until finding a number that's from 5^(i * floor(sqrt(n))).

    Edit: but probably there's a smarter way to solve it, something like getting the answer for 5^x using the answer from 5^(x — 1), since 2^i is a cycle through 5^(x — 1) and probably through 5^x so the answer for 5^x is i * size of cycle + answer for 5^(x — 1).

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

Can someone please explain to me why this submission on problem D passes the pretests?

On the first example test (which is usually the same as the first pretest), it outputs:

2 2 3 4

... implying that you get a score of 2 if you solve problems 3 and 4. But you don't, you get a score of 1 (since problem 3 requires 4 solved problems). Am I missing something or is the judge for this problem broken?

EDIT: nevermind, it seems like I interpreted the statement wrong. I thought a[i] has to be smaller than the total number of problems, but in reality a[i] has to be greater than the total number of problems... and reading through the comments here, it seems like I'm not the only one :P

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3 months ago, # |
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D is straightforward binary search . Lost a good amount of time while debugging C ! :( . bad contest.

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    3 months ago, # ^ |
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    Just because you can't handle overflow doesn't mean contest is bad >:(

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Hello 2018 but with the old name... So sad

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3 months ago, # |
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I find this contest so much better than the good bye 2017. I'm very grateful to the authors.

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3 months ago, # |
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3 months ago, # |
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Correct way to solve C?

Also, hello 2018 and rating drop my old friend...

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    3 months ago, # ^ |
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    Let's update ci: ci + 1 = min(ci * 2, ci + 1). After this we may see that taking away 2N - 1 until L ≥ 2N - 1 is optimal since it's the smallest price we can get 2N - 1 litres for. Then there're two possibilities if there are remaining coins: you either take one more 2N - 1 or go and do the same thing for 2N - 2 till L ≥ 2N - 2 and so on.

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    3 months ago, # ^ |
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    Look at my code

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3 months ago, # |
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check this out that's why you are not red yet :v http://codeforces.com/contest/913/submission/34025378

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3 months ago, # |
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What is TC 8 on problem C all about?

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3 months ago, # |
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include<bits/stdc++.h>

using namespace std;

int main(void) { long long m,n; cin >> m >> n; long long result; result=pow(2,m); cout << n%result << endl;

}

How this code got AC for problem A? I used repl.it compiler and it gave RE.

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3 months ago, # |
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failed :/

and failed :'/

and failed ×_×

...HELLO, 2018!!!

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3 months ago, # |
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Is it just me or you also had these failed problem phases? in all last couple of contests, I had systest failed problems for stupid reasons, in all of them. I'm really stuck in this sh*tty rating because of the HUGE effect that a 1000 or a 500 point problem can have.

You know what's my problem with codeforces? I can solve all of the "easy" problems in a relatively small time, for example, I solved the first four in 49 minutes, not bad, but I'm not using the extra one hour and half for anything (Sometimes hacking, but you always have this belief that you can solve another one). And I'm not alone, usually, the easy problems are solved by more than 1000 people at the end of the contest. the next problem is solved by like 100 people, of course, I can't easily solve it, there are 100+ GMs competing too and they couldn't.

So what's the way for me to get a good rating? submit questions fast, if I don't I will get more penalty and since 1000 people already solved all of the easy problems, I will have a rank like 700+ which is not good. So I have to be fast. Alright, but getting pretest passed is also not a 100% guarantee to get a score of a problem. and when you fail to solve a problem what happens? you go miserably down on ranking.

Even if I have many good contests one after another and I bring up my rating, again there will be another contest, super hard to solve more than 3, and you just need a silly mistake on A to fail and with only B & C for example go down terribly.

I don't care about my ranking, I just don't like the feeling of being stuck in Div.2 for this long. Every time I have to solve things that are not really adding to my knowledge like Div2.A and Div2.B and a lot of times Div2.C.

Tl;dr, I just want sort of contests on codeforces, that have a mellow decreasing number of people who could solve the problems. something like 3000, 1500, 700, 300, 50.

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    3 months ago, # ^ |
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    I believe that virtual participating in previous contests, with practicing on being careful and quiet during reading and solving problems, will decrease the possibility of failing in post-test in real contests.

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

what's the easiest and fastest solution for C?

please explain completely(not just like most of editorials :))

UPD1:I read tutorial and it was easy and fast and complete enough :D

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3 months ago, # |
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Is rating predictor alright? Doesn't seem so by looking at the rating predictions.

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    3 months ago, # ^ |
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    Things got pretty complicated in the predictor due to handle changes (newly-used handles will be identified as new users by the predictor, therefore, the prediction is way too different).

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

one of my friend solve A with cryptography

34024600

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3 months ago, # |
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Where is my problem?My 34026270 of problem C got WA on test case 55. :'( Anyone please help !

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3 months ago, # |
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hi there

i've a question about my problem B

why this 34032197 sulotion should get acc while the MAXN = 1000 & somewhere i've used adj[1000] ????

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3 months ago, # |
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That's the highest upvotes I have ever seen on any post !!!!

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3 months ago, # |
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My submission for problem D, fails on the 23rd test case, but the checker log is weird, I don't have access to the full test case, but my answer seems correct based on the little summary that I can see.

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    3 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    I think this error means that "You said max score possible was 89771 but the score calculated from the indices you printed is 89770"?

    Not 100% sure but it seems this way.

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    3 months ago, # ^ |
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    it says that the 89772 items you chose gave you actual score of 89770 not 89771 as written in the first line of your output, so I think the mistake is not obvious by just looking to the summary

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      3 months ago, # ^ |
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      Yes, I got accepted now. Also thanks to tourist for taking the time to read and debug my code.

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        3 months ago, # ^ |
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        what?

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          3 months ago, # ^ |
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          I messaged him about it.

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        3 months ago, # ^ |
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        Could you explain?

        Why your code gets wa?