Atef's blog

Codeforces Beta Round #83
By Atef, 15 years ago, In English
Hi all,

Today we would like to invite you to take part in round #83 inspired by the ACM practice sessions last year when Dima was visiting the German University in Cairo (GUC).

We have composed the problemset about life in Egypt and the GUC. Hope you will like it :)

The points for the problems in Div 1 & 2 will be: 500-1000-1500-2000-2500.

The writers of the problems are Dima and myself.

We would like to thank RAD, Connector, it4.kp, Delinur, and MikeMirzayanov, who greatly helped in preparing this contest.

We wish you a pleasant, educational and successful contest!

The editorial is under construction.

Good luck to everyone!

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Comments Comments (67)
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15 years ago, hide # |
 
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No. of pariticipants Div 1 and Div 2 are imvalanced. 371 : 1006
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15 years ago, hide # |
 
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Am i able to unregister now?   
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15 years ago, hide # |
 
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It's very weird...
I swear that I've seen the time yesterday and it was 08/23/2011 08:00PM
I miss this game now....
I was torn!!!
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15 years ago, hide # |
 
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when a solution gets hacked and a contestant resubmits.. is his code tested on the hacking test case also??
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15 years ago, hide # |
 
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In my opinion, this contest in div1 was not so good. Very easy problems A and B with really difficult problems C, D, E. As a result more that 200 participants solved A and B and only time to divide them. Of cource, I'm understand that it's really difficult to think of tasks.
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  • 15 years ago, hide # ^ |
     
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    I agree that the gap between number of submissions between B and C was huge, but I think it's really hard to measure difficulty on that fine level.
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15 years ago, hide # |
 
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Are the Java solutions for problem A going to be rejudged?
I sent Java solution for problem A and I got "runtime error", I sent again the same solution few minutes after and I got Accepted, but I guess some points are lost for "wrong" submission.
I noticed the message during the contest that there was some problem with "runtime error" with Java solutions on task A. After the contest I saw that the my first "runtime error" solution was tested again, this time with "Accepted" but I think the points remained the same...
Thanks in advance

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15 years ago, hide # |
 
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Will the contest be "cancelled" for Java users ? I had to resubmit problem A without understanding what was wrong and my B and C failed too (I am not denying that they can be wrong... but it is hard to debug something when the systems preliminary test is not reliable).
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15 years ago, hide # |
← Rev. 2  
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Please Everyone take a look --->

Which one is better translation ??

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"Herr Wafa was also able to guarantee a spot on the team, using his special powers. But since he hates floating-point numbers, he needs your help at finding the probability that he will have at least one teammate belonging to his department."

OR

"Due to their paranormal abilities, Mr. Wafa knew that he really gets into the team GUC. Now he wants to calculate the probability that with him in the team will be at least one student in his department. Since he does not like to calculate with fractional numbers, the task entrusted to you. "
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In the third example, there are three possibilities to compose the team containing Herr Wafa. In two of them the other player from Herr Wafa's department is part of the team.

OR

In the third example, a team which includes Mr. Wafa, can be made in three ways, two of these three comprise the second player from the Faculty of Mr Wafa.
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Comparison of problem setters translation and GOOGLE's translation.
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15 years ago, hide # |
 
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Why the System-testing didn't run yet?
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15 years ago, hide # |
 
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Do I lose a lot of presision by writing
p *= (long double)a/b; instead of
p /= b;
p*=a; ?
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  • 15 years ago, hide # ^ |
     
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    Ok, I had AC with first approach. I just returned -1 instead of 0 when there was only 1 member of sh team...
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15 years ago, hide # |
 
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Так как во время контеста были некоторые проблемы с тестированием решений на Java, то в этом контесте все успешные, но не последние посылки (на претесты) не приводят к дополнительному штрафу, а игнорируются. Еще раз приносим извинения за доставленное неудобство.
=
Since during the contest, there were some troubles with testing Java solutions, all "pretests passed" (except last) submissions do not decrease score, such submissions are ignored. Once again, we apologize for any inconvenience.
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  • 15 years ago, hide # ^ |
     
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    Will it be rated?
    ===
    Будет ли контест рейтинговым?
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    • 15 years ago, hide # ^ |
       
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      It seems yes. It will be rated. If Java issue affected somebody for 10 minutes of more, we can make the contest unrated for him/her. This fact should be proved by submissions log.
      ===
      Похоже, что да. Контест будет рейтинговым. Если на кого-то сильно повлияла эта проблема (10 минут и более), то для него мы можем сделать участие внеконкурсным. Этот факт должен быть доказан логом посылок.
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  • 15 years ago, hide # ^ |
     
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    It is written that such submissions are ignored, but having submitted the accepted solution at 19th minute (after the first ignored submission "00:16:40  Skipped [pretests]" at 16th minuted because of the problems with testing Java solutions) I get 412 points, and other coders get for example 458 points for accepted submission in the 21 minute...

    Will the submissions be rescored after the end of System Testing...?

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15 years ago, hide # |
← Rev. 2  
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What happenes, if I submit a task several times? (all pass pretests)
What if the first is correct submision, but not the second?
How score is calculated?
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  • 15 years ago, hide # ^ |
     
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    What if the first is correct submision, but not the second?

    then you don't solve the problem
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    • 15 years ago, hide # ^ |
       
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      Well, if there is no penalty for second correct submision, I might want to make several submisions "just in case", to make sure I get the right result.

      So, it is a good thing to know.
      I would assume there is a penalty for resubmision, but I wonder, what happens, if 1st submision is correct, but not the second...
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15 years ago, hide # |
 
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problem D ,div 2
is it a Combinations problem?
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15 years ago, hide # |
 
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Can anybody explain - why the answer for
7
1 2 3 4 8 16 32
in B (div 2) is Yes?

if we use x=6553510=11111111 11111111 2 we will get x*x=429483622510 = 11111111 11111110 00000000 00000001 which fits in 32 bits

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15 years ago, hide # |
 
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the test case for problem E in DivI I is so weak...
The passing java code during the contest didn't handle the 
case that there's a rectangle in a empty space surrounding by other rectangles..
Some Sample:

5

0 0 3 0 3 3 0 3

6 0 9 0 9 3 6 3

6 6 9 6 9 9 6 9

0 6 3 6 3 9 0 9

4 4 5 4 5 5 4 5

It gives 1.0571428571428572

obviously the answer is 1

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