MikeMirzayanov's blog

Codeforces Beta Round #40 (Div. 2)
By MikeMirzayanov, 10 years ago, translation, In English
Hi, everybody!

Welcome to the  "Codeforces Beta Round #40 (Div. 2)". Let the weather cloudy (at least in Saratov), and the round began with the unavailability of the server (we apologize for a fail), but I hope the tasks will bring you pleasure.

Wish you high ratings,
MikeMirzayanov
 
 
 
 
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Comments Comments (81)
10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
how can I know the number of the problem which my friends have solve?
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10 years ago, # |
  Vote: I like it +7 Vote: I do not like it
Thanks for the really nice problems.
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  • 10 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Problems were nice. Even though the round was unrated for me, I would like to know what made me got a Presentation Error in Pretest 5 in problem D.
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    • 10 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      And I want to know what was pretest 5 of problem C. I submitted my C# code and got WA. I wrote the same thing with C++ and got acc.
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      • 10 years ago, # ^ |
        ← Rev. 2   Vote: I like it +1 Vote: I do not like it
        show me your code ( http://paste.ubuntu.com )
        may be I can help you
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        • 10 years ago, # ^ |
          ← Rev. 3   Vote: I like it 0 Vote: I do not like it
          THANKS
          Here It is:
          I'm an absolute beginner in C#
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          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

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            • 10 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it
              What's wrong with it?
              input.Substring(0,i) is from index 0 to i-1 and input.Substring(i+2) is from i+2 to end. "at" at indexes i & i+1 was replaced by "@"
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          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

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

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

            → Reply
          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

            → Reply
          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

            → Reply
          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think you have trouble in this part of your code:

            <pre>

            if(input.Substring(i,2)=="at")
            {
            input=input.Substring(0,i)+"@"+input.Substring(i+2);
            }

            </pre>

            reread the statement carrefully ;)

            → Reply
        • 10 years ago, # ^ |
            Vote: I like it +1 Vote: I do not like it
          Here's my code for problem D, in case someone can spot my mistake. Thx in advance.
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  • 10 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    really nice problems!

    thanks to authors and CodeForces!

    well done!

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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I think there will be many pepele died in problem B.

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  • 10 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it
    Well, i've still not understood the problem statement for problem B
    !
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    • 10 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      I missed "not more than once" .The problem mean you can buy and sell only one time or did not do it.Find the max value you can got.
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      • 10 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it
        A simple greedy algorithm works :D
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        • 10 years ago, # ^ |
            Vote: I like it +3 Vote: I do not like it

          Yeah, the problem is simple .Many people make a mistake on what the problem mean.

          → Reply
      • 10 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it
        I think i can only buy once and sell once before.
        But finally i got WA...
        Does the problem means, i can buy many times, but sell only once?
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        • 10 years ago, # ^ |
            Vote: I like it +1 Vote: I do not like it
          Even if you can do so, the best possible thing to do is to buy once and sell once :D
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          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it
            That's not true. In the test: 4 4
            1 2 1 2 you could get more than 8 using 2 sells and buys. By the way, that's a test, which gave me 3 hacks :P
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            • 10 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it
              I don't get the point
              So finally, can I sell many times ?
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            • 10 years ago, # ^ |
                Vote: I like it 0 Vote: I do not like it
              we can not use 2 sells! the statement say only 1 sell....

              when greedy, use:
                  int cas = b / min[i];
                  int t = b + cas * (data[i] - min[i]);
                  if (t > max) max = t;

              min[i] is the min number in the left side.
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              • 10 years ago, # ^ |
                  Vote: I like it 0 Vote: I do not like it
                I did that, but get wrong answer on test 13. My solution was "I can only sell one time" and use greedy like that


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                • 10 years ago, # ^ |
                  ← Rev. 2   Vote: I like it 0 Vote: I do not like it
                  I guess you greedy with the sub(maxPrice,minPrice);
                  Greedy it with the value of you can got with each sub();
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                  • 10 years ago, # ^ |
                    ← Rev. 2   Vote: I like it 0 Vote: I do not like it
                    Yup, like that, I find max value of sub(nowPrice,minPriceTillNow) ,after that result = (b / minPrice) * goodPrice + (m % minPrice);
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                    • 10 years ago, # ^ |
                        Vote: I like it 0 Vote: I do not like it
                      Sorry ,I didnt say correctly.
                      you should greedy the value.
                      value = (b/minPrice)*maxPrice+b%minPrice;
                      not (maxPrice-minPrice);
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                  • 10 years ago, # ^ |
                      Vote: I like it 0 Vote: I do not like it
                    I forgot this, my code
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                    • 10 years ago, # ^ |
                        Vote: I like it 0 Vote: I do not like it

                      Change your loop from single to twice.
                      for (int i=0; i<n; i++)
                          for (int j=i+1; j<n; j++)
                              .......

                      → Reply
          • 10 years ago, # ^ |
              Vote: I like it 0 Vote: I do not like it
            i find my bug, thank you very much.
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10 years ago, # |
← Rev. 4   Vote: I like it 0 Vote: I do not like it
Looks like a lot of people misread problem B and thought that you could sell as much as you wanted.

(bug: commenting seems to not work (comment is blank) from chromium?)
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    It's not a bug in codeforces. I'm writing these in Chromium.
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    The precase is good .The wrong code can pass it.
    So we have chance to hack it.......
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10 years ago, # |
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Can there be more than one word in problem A. I got my solution hacked but still cannot understand the reason
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
How is the Rating calculated? what about the colors (sergeant,lieutenant,etc) ?
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10 years ago, # |
← Rev. 3   Vote: I like it +1 Vote: I do not like it
what is D   test 5?
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    Please give test case number 8,too
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    I got Presentation Erro in that one. I would really like to know what went wrong with it.
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    • 10 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      i have solved my bug .
      PE maybe  you can get the right value, but the wrong path.
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      • 10 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it
        It could be. Anyway, that would be a confussing judge response, in that case a wrong answer should be expected.
        → Reply
10 years ago, # |
  Vote: I like it +1 Vote: I do not like it

admins answer my questions fast during contest , thanks for that.

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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
I found an interesting thing .When we reply a comment, the length of line is shorter than the parent comment.
If we reply the new comment again and again. Will it only print one charactor each line?
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
http://paste.ubuntu.com/528330/


kindly let me knw my mistake......I got wrong answer for pretest 7.....poblem B
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    I think you dont need here any sort function.
    this problem (in my opinion) needs to be solved in one(may be two) for loops - thats all.
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
what is the idea for solving problem E??
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Can you give the test 3 of the problem D? I  get  PE,I'm confused!
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10 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it
Hello. Does anyone know a good article(in english) about using envelopes in dynamic programming? I would really need one.
Thx
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
Some points for Problem D. I think some people may need it.

1. The input data: the first line is the top of chessboard and the last line is the bottom.
2. When you got the max peas value is 0, it has a path, shouldn`t be print -1.(Some people WA on 51 maybe this reason)
3. A 3rd_DP alogrithm can work .dp[ i ][ j ][ k ] express the max peas you can get at point ( i, j ) and the
sum%( n+1)==k. 
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10 years ago, # |
  Vote: I like it 0 Vote: I do not like it
hi
please help me.
in B,What is mean bourles?
and
in C,what is pretest 5?
thanks
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  • 10 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it
    It's a new Russian currency. One bourle = 100 pokeikas  ≈  0.032 laddors.
    → Reply
»
19 months ago, # |
  Vote: I like it -16 Vote: I do not like it

Tranlation https://github.com/arsalanhub/CodeForces/blob/master/Translation

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