KADR's blog

Codeforces Beta Round #97
By KADR, 13 years ago, translation, In English
Hello everyone!

Codeforces Beta Round #97 will take place on Friday, December 9th at 19:00 MSK. This will be my second classical Codeforces round and I hope it won't be the last one :)

I'd like to thank maksay, Shtrix, it4.kp, RAD and Delinur for their help in preparing contest, testing problems and translating them into English.

Good luck!

UPD: Due to technical reasons the round start time is shifted 5 minutes forward.

UPD 2: Due to the large number of participants and large number of tests the testing will finish not soon.

UPD 3: The testing is over. Thanks for participation! I apologize for a very long testing process.

The winners:

UPD 4: The editorial is released.

  • Vote: I like it
  • +237
  • Vote: I do not like it

Comments Comments (77)
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Thanks for your hardwork.

By the way, anyone can explain me what is "classical Codeforces round" means?
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  • 13 years ago, # ^ |
      Vote: I like it +32 Vote: I do not like it
    I can guess that it's a typical Beta round, as opposed to Unknown Language Round or other unrated events with different rules.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Apparently, I accidentally registered twice...
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13 years ago, # |
  Vote: I like it +10 Vote: I do not like it
В связи с изменением формата страниц Codeforces прошу обновить CHelper до последней версии

---

Due to format of Codeforces pages change please update CHelper to the latest version
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Due to bug in build process incorrect jar file was uploaded. Please redownload
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13 years ago, # |
  Vote: I like it +7 Vote: I do not like it
funny, I could challenge one solution with Anti QuickSort, be carefull next time!
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  • 13 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it
    AntiQuicksort detected in final tests
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    • 13 years ago, # ^ |
        Vote: I like it +10 Vote: I do not like it
      There were a few successful hacks made with antiquicksort and they were added to the final testset.
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      • 13 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it
        Are all successful hacks added to final tests?
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        • 13 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it
          Well, I'm not sure about all of them, but most of them are added to the final testset.
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    • 13 years ago, # ^ |
      ← Rev. 2   Vote: I like it +5 Vote: I do not like it

      I forgot that I have antiquicksort generator :(

      FFFFFFFFFFUUUUUUUUUUUU, I also have anti-java-sort generator :(

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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      in last comments someone wrote: "some of challenges are added to system tests"
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Does this mean we shouldn't use quicksort in sports programming?  Is qsort(3) or std::sort safe?
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    • 13 years ago, # ^ |
      ← Rev. 2   Vote: I like it +9 Vote: I do not like it

      I believe C++ STL sort uses introsort so that is safe.

      EDIT: I should say, rather, that GNU C++ does this. The actual standard does not require it.

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  • 13 years ago, # ^ |
    ← Rev. 2   Vote: I like it +5 Vote: I do not like it

    quick sort has random parts, hasn't? so what the hell is Anti Quicksort? :D

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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      In practice a lot of quick sorts are implemented by taking the median of the first, last and middle element instead of using random. This has been shown to give great performance in practice.
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13 years ago, # |
  Vote: I like it +11 Vote: I do not like it
I hope that today system testing will be fast...
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13 years ago, # |
  Vote: I like it +5 Vote: I do not like it
Great contest! Questions was so interesting! Thanks Codeforces that cause me to advance a lot in algorithms!
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
I am baffled, and I tried for ages to figure out why my B.cpp kept failing the very first pretest.

http://pastebin.com/Jpa6M6DX

Things like the paralel and area check I added after trying many things. Initially I only had distance and perpendicular checks. I noted that Romka passed system tests using only distance and perpendicular checks, and his method to check if there is a right angle is equivalent to mine. So, really any help is appreciated.
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  • 13 years ago, # ^ |
      Vote: I like it -14 Vote: I do not like it
    "Romka passed system tests"

    Do you see the system tests finished? I see "Pending system tests". Codeforces system testing uses to start early is it something happening now that doesn't make possible to start system testing?
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    • 13 years ago, # ^ |
      ← Rev. 2   Vote: I like it 0 Vote: I do not like it

      I meant pretests, my problem is that I can't pass even pretest #1

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  • 13 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it
    Also, isn't it usual for pretest#1 to be the example case? If that is the case then this is very strange because the examples work correctly in my machine. If that's not necessarily the case, that's good to know.
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    • 13 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it
      Pretest #1 is always the first example case.
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      • 13 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it
        Thanks. Though I am now officially confused.

        Maybe it is something about compiler versions being different.
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        • 13 years ago, # ^ |
            Vote: I like it 0 Vote: I do not like it
          Maybe garbage in variables?
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        • 13 years ago, # ^ |
          ← Rev. 4   Vote: I like it 0 Vote: I do not like it

          I run your program in my machine

          First case
          your output
          YES
1 2 3 4
5 6 7 8
          but it have to be
          YES
          5 6 7 8
          1 2 3 4

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          • 13 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it
            I get the correct result in my computer. I will try getting identical compiler setup to CF.
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            • 13 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it
              I have been using gcc 4.2 to compile and test locally. If I change it to 4.3 , I start getting WA in the first case. CF uses 4.6 , so there's probably a change in 4.3 that stayed.

              I guess it would have been better to figure out that pretest#1 was the first example, that way I would have focused on compiler-related things.
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              • 13 years ago, # ^ |
                ← Rev. 2   Vote: I like it 0 Vote: I do not like it

                Edit: No, wrong theory.

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                • 13 years ago, # ^ |
                    Vote: I like it +4 Vote: I do not like it
                  I just forgot a "return false" in isRectangle(), this caused undefined behavior, so it behaves differently in different compiler versions.
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        • 13 years ago, # ^ |
          ← Rev. 3   Vote: I like it 0 Vote: I do not like it
          ignore
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          • 13 years ago, # ^ |
              Vote: I like it +4 Vote: I do not like it
            he first make 
            while( cin >> x[0] >> y[0] ) 
            then read other data in loop 1->8
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13 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it
div1.C, when the digits on the cards got blurred, do the players know the
digits? How do they make their decisions?
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Yes, they know the digits. One need to find the outcomes for all possible replacements of '?' with '0' and '1'.
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13 years ago, # |
  Vote: I like it +5 Vote: I do not like it
Very nice problem set, thank you for this competition! :)
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Tottally off-topic but I don't know where to ask. What is the contribution in CodeForces?
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    It's something you gain/lose writing your comments/blog:)
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
We have been waiting 1 hour for less than 20% done of the system test! :(
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
one of the finest set in code forces.......thanks to KADR......... :)
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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
As the codes are tested in the same order they are submitted, don't you think it may be a good idea to show the time when the last tested code was submited during the system tests?
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  • 13 years ago, # ^ |
      Vote: I like it +17 Vote: I do not like it
    You can open the "Status" tab and watch it there.
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13 years ago, # |
  Vote: I like it +8 Vote: I do not like it
Was this was really necessary to make 100+ test cases? If you only keep tricky cases then may be 50> case could be enough for testing and will take smaller system testing time :-|
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  • 13 years ago, # ^ |
      Vote: I like it +10 Vote: I do not like it
    Most of the successful hacks were also added to the final testset.
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    • 13 years ago, # ^ |
        Vote: I like it +34 Vote: I do not like it
      For the next time it may be a good idea to make the tricky test cases be the first one so there's no need to test 200 cases before test case 201 fails.
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13 years ago, # |
  Vote: I like it +15 Vote: I do not like it
It would have been better to include the cycle
11
11
in Div1-D sample tests.
Many didn't pass the pretests because of this.
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13 years ago, # |
  Vote: I like it +6 Vote: I do not like it
I just saw the solution to Problem B Div 2, Lolz, my solution to the problem is so crappy !! I can't believe it didn't strike me. Well, you always learn something new here. :)
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13 years ago, # |
  Vote: I like it +18 Vote: I do not like it
too slow system test :(
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
Now around 2 hours waiting and only less than 50% done of the system test! :\
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13 years ago, # |
  Vote: I like it +8 Vote: I do not like it
f5 after f5, tired :(
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  • 13 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it
    f5 will be broken tonight...
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      surely :)
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    • 13 years ago, # ^ |
        Vote: I like it +16 Vote: I do not like it
      I'm not sure if the system testing is done on the same server, but if that is the case, ironically, pressing f5 will only make it slower ;)
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Count them so you don't get bored :D
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    • 13 years ago, # ^ |
        Vote: I like it +9 Vote: I do not like it
      :( I lost my count somewhere after 999997
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      • 13 years ago, # ^ |
          Vote: I like it +6 Vote: I do not like it
        And the waiting world record goes to the guy who submitted last.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
At last! :)
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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
Great contest, I really enjoy, thanks to all whose work makes it possible  that this site is.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
I think Petya is the person who enjoyed the contest most. He received a lot of gifts from his mother in this end of year! Wondering if it could happen to us...
Seriously now, the system test case took really a long time, but ignoring this fact, I liked the contest. I think the problems difficulty were indeed propotional to the problems' points/values, and the statements were easy to read.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Great contest!
By the way, anyone can give me some ideas to solve problem E-div2?
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13 years ago, # |
  Vote: I like it +2 Vote: I do not like it
the meaning of problem A is ambiguous.


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13 years ago, # |
← Rev. 6   Vote: I like it 0 Vote: I do not like it

really enjoyed the contest, thnx  KADR. wish I didn't make a stupid mistake in D :(

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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    really enjoyed the contest, thnx KADR. wish I didn't make a stupid mistake in D :(

    example =)
    read this.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
I failed in case 222 in problem 'Rectangle and Square' and I can't find what the problem is in my code, did anyone encountered the same problem? May anyone help?
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it 
    0 0
1 0
2 0
1 2
    This isn't a valid rectangle.
    Input:
    0 0
1 0
2 0
1 2
50 50
50 51
51 51
51 50
    Output:
    NO
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  • 13 years ago, # ^ |
    ← Rev. 2   Vote: I like it +1 Vote: I do not like it

    Check the part of your code where you check whether it is a rectangle or not.

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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      Oh you are right :) .. I didn't think of such a case.
      Thanks.
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
What is Test#7 in Problem D in Div1 (Cycle)?
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Go to your submissions and left click on the number of your submissions and scroll to the bottom. In your case you need submission 951386.

    Test: #7, time: 10 ms., memory: 37576 KB, exit code: 0, checker exit code: 1, verdict: WRONG_ANSWER
    Input
    4 5

11111

10101

10001

11111
    Output
    15
    Answer
    0
    Checker Log
    wrong answer 1st numbers differ - expected: '0', found: '15'
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13 years ago, # |
  Vote: I like it +15 Vote: I do not like it
when will the editorial for the contest be available ?
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Russian version of the editorial is already published. I'll translate it today or tomorrow.
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