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Codeforces Beta Round #84
By witua, 13 years ago, translation, In English
Hello!

Welcome to Codeforces Beta Round #84! I am Vitaliy Herasimov (witua) and I am an author of today's problems. Thanks to Artem Rakhov (RAD) and Pavel Kuznetsov (it4.kp) for the help and advices in preparing of the rounds, Maria Belova (Delinur) for the statements translation.

Good luck!

Contest is over! Congratulation to winners!

Division 1:
  • Vote: I like it
  • 0
  • Vote: I do not like it

Comments Comments (63)
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13 years ago, # |
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It was weird because it had no comment. So writing the first comment :  thanks witua. (for preparing and creating problems.) 
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  • 13 years ago, # ^ |
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    There are 18 more comments in Russian interface, so yours is not first :)
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    • 13 years ago, # ^ |
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      But i was the first in an international version of codeforces. :) 
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      • 13 years ago, # ^ |
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        Then international part of Codeforces must know:
        today is birthday of author of this contest, witua
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        • 13 years ago, # ^ |
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          Wow. I remember that one of previous contest's author's birthday was on the day of his contest, wasn't it? Anyway Happy Birthday Vitaliy Herasimov (witua)
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    • 13 years ago, # ^ |
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      As I can understand from the Russian version of this site, today is the birthday of witua. Happy birthday, Vitaliy :)
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13 years ago, # |
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good luck and have fun ~~
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13 years ago, # |
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I hope I don't make any silly mistake. :)
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13 years ago, # |
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Uh, yeah...

Good luck everyone.
:)
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13 years ago, # |
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Short statements :D
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13 years ago, # |
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I think div1 B, the writer'solution is wrong.
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  • 13 years ago, # ^ |
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    Then most of coder's solutions are also wrong)

    I think that writer's solution is correct... And you just have to search mistake in your own.

    Today's div1 B is pretty one)

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    • 13 years ago, # ^ |
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      I don't think so.
      I made 4 chas, and now 2 of them were earsed.
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    • 13 years ago, # ^ |
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      I made a hack with "7 7 7 7 1" at the time 27:33 after this round begin.
      The system return with
      Solution verdict:
OK
Checker:
ok found '2.0000000000', expected '2.0000000000', error '0.0000000000'
Input:
7 7 7 7 1
Output:
2.0000000000
Answer:
2.000000000000

      which means the answer is more than 1, is totally wrong.
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      • 13 years ago, # ^ |
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        Unrate this round.
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      • 13 years ago, # ^ |
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        It seems that in this round will be total rejudge and score shuffling again, just like in previous.
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        • 13 years ago, # ^ |
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          My solution for B was challenged and the challenge was cancelled. I think the author's solution was already fixed.
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      • 13 years ago, # ^ |
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        How did you see the exact verdicts between the contest.?
        Is it only at the time of hacking or in general that we can see the test case.
        Please tell me because I am new here and I have never hacked
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        • 13 years ago, # ^ |
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          You see the hack hase if you're the hacker ;) The hackee doesn't.
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        • 13 years ago, # ^ |
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          You can see the verdict with answers only after locking your problem and hacking others code. It's OK because after locking you can't resubmit.
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  • 13 years ago, # ^ |
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    This problem in the writer's solution influenced 2 hacks: yours and ilyakor's. The solution was fixed in 13 minutes, and hacks were rejudged. We are extremely sorry for this.
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13 years ago, # |
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LUCKY NUMBERS. I love 4 and 7 :). It was the greatest contest I have ever attended since my first competition on codeforces.   I want more contests from witua . 
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13 years ago, # |
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I have submitted E, but it will fail (TL) on such case:
699999999 9

Try this test before system tests if you have submitted.
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13 years ago, # |
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nice problems.happy birthday witua .
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13 years ago, # |
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nice contest :-)
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13 years ago, # |
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i love this contest :) .........better than using topcoder appelet
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13 years ago, # |
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great contest.Short questions..nice work witua.
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13 years ago, # |
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I love the contest . Happy birthday , witua.
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13 years ago, # |
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Loved the problem statements. No unnecessary description. Easy to understand. Thanks very much witua :)
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13 years ago, # |
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Congrats to rng_58 and Petr for solving all of them :)
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13 years ago, # |
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Hi!
I think the "lucky number" thing was good and bad. It was good because it made the statements easy-to-understand, it was bad because it kind of "limited" one's range of thinking. But I think the goodness beats the badness :)
When will the editorial be up?
BTW, Problem C in Div. 2 was easier than Problem B for me :D
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13 years ago, # |
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Has anyone noticed that right now there are two leaders at Codeforces? Both tourist and Petr has the same rank :)
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  • 13 years ago, # ^ |
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    Yes, but there's also a bug :D ACRush should be 2nd now, not third :)
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    • 13 years ago, # ^ |
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      That's not a bug. There are 2 guys (Petr and tourist), who have larger rate, than ACRush. So, he is 3rd.
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13 years ago, # |
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So you're saying that there's no one in second place? That's impossible ( Unless the number of contestants is less that two, which isn't happening in this case ) :D
Every place should be filled by at least one contestant; 1st was filled by 2, That doesn't mean the two contestants who are in first place also filled the second place, does it?
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13 years ago, # |
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http://www.codeforces.com/contest/110/standings
Some anomaly, see vihrov's score for Prob A.
He has two WA's still no -50.  :S
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13 years ago, # |
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Here's a code for Div2- C, which gives Runtime Error on the codeforces judge test case #44, but it's running perfectly fine on my system. Please help.

Edit: Ok,the code works fine when I made the ar[][] global, but still even when the ar[][] is declared inside the main(), it should work right ?? At least it does in my system and also on Ideone.
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  • 13 years ago, # ^ |
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    When you place this array inside a function (and consequently main), it is pushed to the stack that isn't large; on the contrary, if you make it global, it is placed on the heap, which can hold much larger structures than stack (also, read here). With trial and error I found out for myself that it is better to put something on the heap when the size is counted in millions or more.
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    • 13 years ago, # ^ |
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      But the case for which it is failing, that has N=2. It passed the earlier test case with much larger N.
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      • 13 years ago, # ^ |
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        Well, you changed your code; and now it has a different kind of error: you go out of array bounds in 
          1.  ar[4][0]=1,ar[4][1]=0;
          2.  ar[7][0]=0,ar[7][1]=1;
        since if n = 2, it has size 3 in first dimension.
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        • 13 years ago, # ^ |
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          Oh yes !! So silly of me i didn't note that :)
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13 years ago, # |
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This contest proved two things.........
1.Standard contest can be arranged by simple and easy to understand statements.
2.There can be a wide variety of problems derived only from a basic concept(in this case it is lucky numbers).......

Thx witua and happy birthday..................
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13 years ago, # |
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Thanks for the short and clear problem statements.
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13 years ago, # |
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I am another coder who is showing his pleasure for the short statements, really nice contest. I also love tales and universal history, but in programming contests only a fast and tricky AC, or slows and painful WA/TLE will give you fun and knowledge.
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13 years ago, # |
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Lucky numbers of names presented for each division! Great contest, i liked the theme
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13 years ago, # |
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I found a mysterious problem about Div2 D. Here is my code.
On Codeforces, my code seems to output a wrong answer against to test 3 which contains "1 20 100 120 5". And the wrong answer is "0.15", while the correct answer is "0.2". On the other hand, on my computer, my code outputs "0.2". It is not a wrong answer, and I can not understand what happened. Of course, I confirmed that I have not submitted a different code.

My local environment is as follows,
Mac OS X snow leopard
% ~/ruby1900/bin/ruby --version
ruby 1.9.0 (2007-12-25 revision 14709) [i686-darwin10.8.0]
% ~/opt/bin/ruby --version
ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]

With both versions of Ruby, my code outputs "0.2".
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  • 13 years ago, # ^ |
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    you misread the test case,
    "Output" is the output of your program, in this case 0.2
    "Answer" is the right answer for the test case which is 0.15
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    • 13 years ago, # ^ |
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      Thank you for your reply. And I apologize for my ridiculous mistake. Thank you, 0x1337.
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      • 13 years ago, # ^ |
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        No problem,
        I also got confused by this("Output & Answer") at first.
        Maybe instead of "Answer", "Judge Solution Output" would be better, i don't know.
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13 years ago, # |
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If you look at the final standings Petr had solved all the questions in 1:38 while rng_58 in 1:40 but score of rng_58 is 5894 while that of Petr is 5566.This teaches us something.Order of solving questions can also make an impact on the final standings!!
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