witua's blog

Codeforces Beta Round #77
By witua, 13 years ago, translation, In English
Hello everyone!

Welcome to Codeforces Beta Round #77. I am Vitaliy Gerasimov (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 problem translation and Codeforces (CF) for being.


Good luck!
  • Vote: I like it
  • +160
  • Vote: I do not like it

Comments Comments (107)
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13 years ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

gl & hf!

P.S. разбаловка  обычная?
P.P.S. Sorry, this comment must be in russian, not in english
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13 years ago, # |
  Vote: I like it -11 Vote: I do not like it
May be one of the problems on "lucky numbers" ?... looks like it.
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13 years ago, # |
  Vote: I like it -6 Vote: I do not like it
How many minutes before the round, the problemset is disabled ?
(I just read 1 problem and wrote the solution, and when I clicked submit , it was disabled. So thought , it would be good to know exact timing.)
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  • 13 years ago, # ^ |
      Vote: I like it -13 Vote: I do not like it
    rng_57 your color was red, isn't it? when it became green? 
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  • 13 years ago, # ^ |
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    you must find your contest by trying :
    for example link of CF #76(div2 only) is : http://www.codeforces.com/contest/94
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    • 13 years ago, # ^ |
        Vote: I like it +1 Vote: I do not like it
      Thanks. I submitted my solution. :)
      (looks like problemset is completely disabled but /contests/ links are working.although links do not appear on contests page.)
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13 years ago, # |
  Vote: I like it +9 Vote: I do not like it
Fighting!
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13 years ago, # |
  Vote: I like it +4 Vote: I do not like it
Good Luck everyone !  /Амжилт! in Mongolian/ :)
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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
where is the list of registered contestants?
I can't submit because apparently I'm not registered.
I thought I did register...
Thanks
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  • 13 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it
    Was it because you were not logged in *WHEN* you clicked the "register" button?

    If it was so, you would not be directed to the registration page. I missed two or three contests because of this reason...
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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
This is the second time I can't submit on CF in a contest, I guess there's something wrong with my Internet...
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    I can't submit either!  :(
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    • 13 years ago, # ^ |
        Vote: I like it +6 Vote: I do not like it
      Yeah, it's weird, the whole site is working but when I click submit it doesn't work...
      I wonder what could be the reason. :)
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      • 13 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it
        mine is the same, but it seems that no one else has this problem.
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
Now I understand why the problem with the lucky number. It's so great.
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13 years ago, # |
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Won't have much time to solve E :(
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13 years ago, # |
← Rev. 2   Vote: I like it +20 Vote: I do not like it

Div2.C is too hard to understand.
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13 years ago, # |
  Vote: I like it +11 Vote: I do not like it
Div2 C problem.
if (w[i] == letter && letter == 'a') replace_with('b')
is awesome tricky :)
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13 years ago, # |
  Vote: I like it -52 Vote: I do not like it
I think that the user 

wclee2265

is a cheater. He has only one minute between two submits for problems A and B (Div 2). More than that, he solved them quite late. The source code for problem B is quite huge. Admins, please, check this out :) 
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  • 13 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it
    He may submit A and then make quick fix for B and submit it as well
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    • 13 years ago, # ^ |
        Vote: I like it -17 Vote: I do not like it
      Thats why I said "I think", but not "It's obvious that".
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      • 13 years ago, # ^ |
          Vote: I like it +62 Vote: I do not like it
        I think that public accusations is not the right thing if you in doubt yourself. You can always contact admins via PM
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        • 13 years ago, # ^ |
            Vote: I like it -9 Vote: I do not like it
          I dissagree with you. In this forum user can prove that he is not a cheater.
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          • 13 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it
            Why should he do this? He might not read this discussion at all.
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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
Div2 C problem
Why the output of the third text is abCacba,not abCccba.It is hard to understand.
 
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Pretty sure you MUST change every character that can be changed. So you can't change the middle 'c' to a 'c'. You have to change it to something lexicographically small, i.e. 'a'. It took me a while to realize this...
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Because you 'must change' the character. And the best possible substitute is 'a' (lexicographically least)
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  • 13 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    You could have asked the author ,this same question during the contest to get it clarified then and there.
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Yes.You are right.It is a regret that I hav't  asked the author.

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    • 13 years ago, # ^ |
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       I think it is better that the author can explain the third text below the problem.But it will reduce the difficulty of this problem.
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  • 13 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it
    Did anyone get run-time error on Div2 Prob C.
    (on test 21 or any other, and how did you correct it?)
    I am unable to see whole testcase.
    I request the  author to give me pastebin/ideone link for Test No. 21 .
    I will be highly thankful.
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      I have same problem, A div1
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      • 13 years ago, # ^ |
          Vote: I like it +6 Vote: I do not like it
        May be in the statement:
         for(i;i < a.size() - b.size() +1; i++)

        unsigned integers should not be compared with signed ones.....

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        • 13 years ago, # ^ |
            Vote: I like it +1 Vote: I do not like it
          Yes, u'r completely right, see my comments below
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          • 13 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it
            Yes, thanks.
            Actually I saw the RE and AC codes of bloops  ,then came to know.
            So, You and bloops gets full credit from my side.
            Thanks to bloops too.(may be he doesn't even know that he helped me)
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      May be someone will find the bug:
      http://ideone.com/Z2eS6
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      • 13 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it
        The problem is in line # 82.
        You forget that container.size() return unsigned value. Therefore, i.e. when ss[i].length() > s.length() + 3, sz(s)-sz(ss[i])+1 = UNSIGNED_INT_MAX, and u'll be facing problems with memory access.
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13 years ago, # |
  Vote: I like it +15 Vote: I do not like it
I just need one more second to submit D .........T___T
When I submited it after the contest, it got Accepted.....
My heart broke ...........

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  • 13 years ago, # ^ |
      Vote: I like it +43 Vote: I do not like it
    http://codeforces.net/blog/entry/2179#comment-44375
    The Balance is restored. :-)
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    • 13 years ago, # ^ |
        Vote: I like it +11 Vote: I do not like it
      Maybe people have deeper impressions about their unlucky things, but we should know we are lucky in any way :-)
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    • 13 years ago, # ^ |
        Vote: I like it +12 Vote: I do not like it
      Aha, good explanation!
      I'm waiting for such balance take place, because I always make mistakes.
      (For example, in today's Problem C, I forget to use long long somewhere and got WA.)
      Anyway, I should practice more and be more careful.
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13 years ago, # |
  Vote: I like it +16 Vote: I do not like it
Hi, did anyone else have problems with loading the page in the beginning of the contest? It took me 3 minutes to be able to access the contest.
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    I did, too. And once more during the contest.
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Yep, this problem took me three minutes too.
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Yes, me too
    It affected me a lot .....
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    me too..intially for 1 or 2 minutes...
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    yup me too!!
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    At the beginning I simultaneously loaded multiple pages of different problems, hoping that one of these pages could be loaded.
    After struggling for a while, I closed all the pages and retried... and I succeeded when I loaded only one page...

    This took me around ~10 minutes...
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13 years ago, # |
  Vote: I like it +6 Vote: I do not like it
What was the point distribution for the problems in both Div1 and Div2?
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
My Div2.C had a one character bug T_T

This line...
printf("%c", (letter!='A')?'A':'B');

...should be...
printf("%c", (letter!='a')?'A':'B');

...to get Accepted :'(
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13 years ago, # |
  Vote: I like it +11 Vote: I do not like it
@witua, thank you for this nice contest. I enjoy it a lot. Waiting for the editorial.
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13 years ago, # |
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Yet again "an one-liner stupidity" failed my C :( :(.
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13 years ago, # |
  Vote: I like it +4 Vote: I do not like it
This is the first time I can be a red coder. Nice contest, I really like the "lucky numbers" problems both in TC and CF. Thank you author
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13 years ago, # |
  Vote: I like it 0 Vote: I do not like it
What is test #52 in problem 95B (B, div 1) ?
Cause, I cannot find mistake for about a hour, and I really want to sleep xD
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    It's a lucky number with 100000 digits.
    go sleep! =)
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    • 13 years ago, # ^ |
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      Thx. I've already solved it. Really, I need more sleep :)
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      Are you sure? I considered this case independently, but my solution gets WA on test 52. The submission ID is 539553.
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      • 13 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Yes, I am sure. 

        P.S. There is no super lucky number in this case, only lucky.

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  • 13 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    ignore
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  • 13 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    My solution gave RTE on test 52 as well. I was not sure what was wrong because (I thought) I tested it on all possible combinations (of 1,4,5,7,9). Well, turns out I did not. 4 digits were not enough

    For anyone else having the same problem, try this case:

    477747

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13 years ago, # |
  Vote: I like it +17 Vote: I do not like it
I have just noticed this, Codeforces Beta Round #77, it's a lucky number :)
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Div 2 problem D is very nice. Thank you  the author! This problem can train ours ability of thinking about the problem completely.I learned a lot after AC this problem.

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13 years ago, # |
  Vote: I like it +1 Vote: I do not like it
Is the editorial out yet?
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
For me, Div1C/Div2D is easier than Div1B. Latter is just trickier.
Or maybe there is clear implementation to solve it.
Anyway, lucky number reminds me of TopCoder.

For Div1A/Div2C, first I think only given letter is important, so wondered why sample gives upper case letter instead of 'A'.
I think it would be good to add the statement "Both uppercase and lowercase letter are important." to clarify the problem.

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13 years ago, # |
← Rev. 5   Vote: I like it 0 Vote: I do not like it

who can help me solve the DIV1-D problem?I got TLE,55555555
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  • 13 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    I guess I know this "55555555"  ....  does it sound like crying in chinese..?.
    I see a lot of these during SRMs when someone misses to register by 1 minute or so....they say i missed the match "5555555555".
    Am I correct ?
     
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    • 13 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      yes，you are right~
      But I want to know how to solve this problem? Can you help me?
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13 years ago, # |
  Vote: I like it +5 Vote: I do not like it
When will the editorial for beta round - 77 be released..??
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
thnx (imslavko + google translate) :)
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13 years ago, # |
  Vote: I like it +3 Vote: I do not like it
well, since a lot of coders are not from Russia and hence don't understand Russian- quick skimming through rating pages by country says that non-Russian coders are half of the coders here-, why is the editorial not written always in English ? why writing it in Russian in the first place ? 
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  • 13 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it
    There is English translation here.
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    • 13 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it
      thanks a lot, that resolved the problem :) but still I'm wondering why not writing it in English from the beginning..
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      • 13 years ago, # ^ |
          Vote: I like it +2 Vote: I do not like it
        Because e.g. I can write it in Russian in 10 minutes and in English in at least 30 minutes. And my English is from my heart.
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        • 13 years ago, # ^ |
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          hmm ,okay :) I wish I could learn some Russian from the editorials then :)
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13 years ago, # |
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Div1 D - In the first paragraph 412395497 is given as nearly lucky for k=2. The first digit of the number is 4 and it does not have another lucky number within distance 2. Can someone explain how this is nearly lucky number?
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