MikeMirzayanov's blog

Codeforces Alpha Round #21 (Codeforces format)
By MikeMirzayanov, 14 years ago, translation, In English
I invite you to participate:) Round will be non-rated, but there will not be limited registration at this time! Please, read the rules before the contest!
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  • +18
  • Vote: I do not like it

Comments Comments (30)
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14 years ago, # |
  Vote: I like it +5 Vote: I do not like it
Can you lock a problem without solving it? Maybe I would like to challenge bad solutions for a problem that I don't know how to solve.
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14 years ago, # |
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Sounds interesting. :)

Could you point me to a description of how the Codeforces format works exactly, or if that doesn't exist, quickly summarize it for those of use who haven't participated in any of these contests yet?
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14 years ago, # |
  Vote: I like it +3 Vote: I do not like it
Ok, the round seems (almost) over and so I will share my impressions.

The first thing I want to say is that I had much fun hacking the solutions, even though almost every solution I hacked had the same bug as mine :)   Eventually, I've received more points in hacking solutions for the first two problems than I possibly could by solving them.

However, I couldn't get used to the way the contest proceeds - i.e. instead of solving the problems I checked my room every minute for new submissions. Did anyone else get distracted by hacking opportunities? :)
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  • 14 years ago, # ^ |
      Vote: I like it +13 Vote: I do not like it
    Hm, 16th place with a single problem solved.Wish the round was rated :)
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14 years ago, # |
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Empty cycle of length 0 is bad thing (test 9, problem D).
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  • 14 years ago, # ^ |
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    I mistaken, that's other test. What is test case #9?
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    • 14 years ago, # ^ |
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      forget it. Found a bug :)
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      • 14 years ago, # ^ |
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        How you guys generate the  hacking test cases during contest. Is it using program or paper/pencil? What would you suggest  to me to become a master in generating test cases.?

         
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        • 14 years ago, # ^ |
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          Just look at the code and see what's wrong with it. If you solved the problem yourself, it shouldn't be difficult.
          Also, while you're coding, remember what pitfalls you had to escape and search for similar mistakes during hacking.
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      • 14 years ago, # ^ |
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        How you guys generate the  hacking test cases during contest. Is it using program or paper/pencil? What would you suggest  to me to become a master in generating test cases.?
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14 years ago, # |
  Vote: I like it +4 Vote: I do not like it
Is it just me or everyone has this awful font in the code window?
http://img96.imageshack.us/img96/9440/44506589.png
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14 years ago, # |
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The Problem Stripe2 :
          My solution got TLE on test14 . Is it because i solved it in O(n 2) ??

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14 years ago, # |
  Vote: I like it +8 Vote: I do not like it
What an amazing contest!
And I want to know : why the page "room" refreshed when I reading others codes?
Is that means some success hack take place?

By the way , my hacks : id = "545" and id = "525" is waiting , until now.
I just upload a program generate a test case that N = 100000.

And I didn't take care of "The length of <hostname> is between 1 and 32, inclusive." in problem A , but I passed all final test case.
Is that all of the test cases from successful hacking add to the final test , like TopCoder?

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  • 14 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it
    ya, seems the room gets refreshed now and then.. and doesn't restore the code window we are looking at then.
    .
    Overall, the new rules are good, except that 'm more concerned about, 'ok.. lets stop coding and start hack', and kept on refreshing the room tab. There is a slight chance that I may get one more question correct if I put more time in coding, without any such concerns. May be, hacking should be enabled only in the last 25% of the total contest time. 
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    • 14 years ago, # ^ |
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      I think there's a fun strategic element in figuring out when you should stop solving and start hacking. To that end, I think you should be able to hack whenever you want.
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14 years ago, # |
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Hmm, where can i find information about that "hacking" option ? How can i hack someons solution ?
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  • 14 years ago, # ^ |
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    It's written when you enter your room:
    You may double click into cells (or ctrl+click) to view the submissions history or hack the solution
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14 years ago, # |
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Can i see which test case was used to hack my solution ?
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  • 14 years ago, # ^ |
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    Yes you can, open the "Hack" section in the contest and look for yourself on the "Defender" column. As i can see the Attacker was Petr and the test case was :
    0 0 1
    0 0 1

    Expected 0, found -1.

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14 years ago, # |
  Vote: I like it +5 Vote: I do not like it
I don't really like how it's set out currently. Being able to hack through the entire time doesn't really help out average people - who spend more of the time coding anyway - but the best users can use it to their advantage to totally dominate. 

You guys are obviously trying to stray from borrowing a lot from topcoder, but in your strive to be different I think you made the system overly discouraging to beginners.

Further, the 'pretests' didn't seem to be very comprehensive; I passed them all the first time, only to have all my solutions killed immediately after.

To solve both these problems, I think you could make the pretests more difficult to pass. This doesn't seem to have many disadvantages. It would help out beginners without hindering more experienced participants.

It's very discouraging to see all your points dwindle away!
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  • 14 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    I think for the beginners it's important to concentrate fully on the solving part. Only after you feel you can't solve anything more, you can lock your problems and try to hack someone.

    As for the new format, I also think that the ability to code and hack at the same time make no sense. The contests become more like a game. And the genre is real-time strategy :) Like WarCraft or something... I hate this kind of games so maybe that's the reason I feel this way about the new format.
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  • 14 years ago, # ^ |
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    Actually, this system is better for beginners (compared to topcoder), because their solutions can be checked by strong coders. It can increase the gap between best and medium coders, but remember, not all problems will be so 'hackable' as in these alpha rounds.
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14 years ago, # |
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how can i solve the problem D?
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  • 14 years ago, # ^ |
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    http://en.wikipedia.org/wiki/Route_inspection_problem
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14 years ago, # |
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I and my brother found a test that is not included in the test cases but will fail at least him if we add it.
We are talking about problem B. If you give us:
0 2 3
0 5 11
He answers -1 but the correct is 0. Can this test be added to the test cases?
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