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MikeMirzayanov's blog

By MikeMirzayanov, 10 years ago, translation, In English,
I propose to discuss here all that concerns Codeforces Beta Round #3. Of course, during the competition it is forbidden to write anything about the solution of problems and similar things  

For the time of this contest, we turned off the chat server. This does not mean that it will not operate in future - I think it is a convenient and efficient way to communicate during the competition and you may expect it in the future.  

Also I'd like to announce Codeforces Beta Round #4, which will be held next week. It will be for participants from the second division (non-rated users or those having less than 1500 rating points). We will try not to delay Codeforces Beta Round #5, which will be opened for all. 

Wish you high rating,
MikeMirzayanov
Announcement of Codeforces Beta Round #3
Announcement of Codeforces Beta Round #3
 
 
 
 
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10 years ago, # |
  Vote: I like it +1 Vote: I do not like it
Hmnn well.

Problem A: It said that both the first and second lines would contain t. I had no idea where to report it but I guess everyone was able to get around it.

Problem B: It was not clear at first that the second line of output should be a space separated list, again I had to guess and hope for the best. For that matter, I wish the example required two vehicles in output...

Problem C: Nice trickiness.

Problem D: I wish I didn't lose so much time on implementation of the other three problems because this seems like the only truly interesting one of the set :)

I like that it tells you the number of test it is running.

At one moment I had two tests in queue for the same problem, because I noticed too late that the first one was running 1000 random test cases... I think that instead of having both soltuions in the queue, after submitting the second one, the first should get a "Cancelled" and get penalization. Else you could just submit slow solutions and forbid queue usage from the rest of the teams...
10 years ago, # |
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i think you should do something with being in queue for 10 minutes, especially if there will be more then thousand contestants, and what do you think about posting tests in practice room, or to show the test, with witch your program works incorrect 
10 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Hello, maybe I missed that while reading other posts regarding the contests. Is there some pseudoconstant defined on the server? It would be a nice thing, in that case the contestants won't have to deal with streams.

For example, right now I use the following trick:

#ifndef USE_ONLINE_JUDGE
 freopen("input.txt","rt",stdin);
 freopen("output.txt","wt",stdout);
#endif

And before sumbitting I have to add the line manually in the beginning of the source code:

#define ONLINE_JUDGE

  • 10 years ago, # ^ |
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    Regarding that - it would nice, if there would be something like FAQ on this site, since right now newcomers have to read posts that are not sorted in any way.
    • 10 years ago, # ^ |
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      Regarding suggestions, please allow us to undo "I Like it" or "I don't like it" votes, because sometimes you accidentally click on one when you meant the other...
10 years ago, # |
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Will you publish test data after the contest?

I think it will be helpful (for educational purpose) because it's quite difficult to find bugs when the solution fails in tricky case.
  • 10 years ago, # ^ |
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    I think that for your faster growth in programming competitions it will be better if you find bugs by yourself. Learn to carefully test your program, verifying is't correctness on different corner cases or doing a stress-test with some brute-force solution.
    • 10 years ago, # ^ |
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      He is a target :P
      • 10 years ago, # ^ |
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        No excuse. A shame for a target on TC to suggest such things.
        • 10 years ago, # ^ |
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          i think you should do all what you've said at contest, but then you may watch tests
      • 9 years ago, # ^ |
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        Moreover, he is the TCO 2010 Algorithm champion
    • 10 years ago, # ^ |
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      I like Your Spirit!!!!!!!!!!!!!
    • 10 years ago, # ^ |
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      Thank you for suggestion. I'm interested in how other people debug during competitions, especially when the solution fails several times. Do you use stress-test?

      But I think it would be nice if test data are published because it's not always possible to solve problems by oneself.

    • 10 years ago, # ^ |
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      I don't see how would not getting test data at all after the contest is going to help to anyone's growth at all. Why if in one contest there is wrong judge data? Transparency is good and as it was mentioned rng is already a target so he does not really need that much growth...
  • 10 years ago, # ^ |
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    I think you are wrong here. As far as I understand, only TopCoder does that (i.e. publishes all the test data), for ICPC competitions that's very uncommon. Still, editorials for problems are published here, and you should be able to implement the correct solution after reading it. So the test data is not quite necessary here...
    • 10 years ago, # ^ |
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      At the ICPC  tests are usually available after the competition.
      Tests are not published mainly in the online archives, which are rating.
      By the way, If you want to solve the problem yourself, nobody forces you to watch tests.
    • 9 years ago, # ^ |
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      But nowadays Codeforces is becoming less and less looking like an ACM ICPC competition or online judge, but gaining more of TopCoder features (such as challenges, contests duration, and etc.). So I think it is ok to talk about the test data availability
  • 7 years ago, # ^ |
    Rev. 26   Vote: I like it -6 Vote: I do not like it

    hacked by hackers

10 years ago, # |
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Also, it would be great, if the problem statements would contain more than just one sample test. I think one test sometimes is not enough to be sure, that your implementation works correctly. Of course, there is no need for the complete test coverage (I remember a couple of TopCoder problems, there the sample test suite contained all classes of possible tests, and therefore the solutions that passed them also passed the system tests with 100% guarantee).
  • 10 years ago, # ^ |
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    The sample tests are not for checking whether your solutions is right or not. They are to help you understand the problem so in most cases one is enough.
10 years ago, # |
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Finally I found why my solution failed on Problem D. Please read this thread : http://forums.topcoder.com/?module=Thread&threadID=666676&start=0

It was compiler's problem related to printf. (I'm not complaining, because it's not CodeForces's fault at all.) But I suggest to publish test data and enable us to run solutions on the CodeForces's system to find such bugs as easy as possible.

  • 10 years ago, # ^ |
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    I think publishing test data is a very good idea, but would like to add that all submitted solutions be also made available (as in TopCoder). Having the code would be an invaluable resource for learning.
10 years ago, # |
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When is the next round?
I would suggest if you could keep the calendar as a Google Calendar, it will be very convenient and also be displayable easily in a web-page.

Thanks for this amazing site!
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4 years ago, # |
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Can someone help me? 10970260 is my submission ID, which is getting invalid output format. Although it is giving correct output format on my machine.

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4 years ago, # |
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The link for the tutorial is broken?

I mean the link shown in the contest material part in http://codeforces.com/contest/3/

edit: Dont quite understand the downvotes... Is this actually fixed?