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Round #43 with prizes (unusual start time)
By csacademy, 7 years ago, In English

Hello, Codeforces!

We're going to host a new contest at csacademy.com. Round #43 will take place on Sunday, 27/August/2017 12:00 (UTC). This contest will be a Div1 + Div2, with 7 tasks of varying difficulty that need to be solved in 2 hours.

We are glad to have lucyanna2018 as a problem author.

Prizes

We're going to award the same prizes as the previous Div. 1 + Div. 2 rounds:

  1. First place: 100$
  2. Second place: 50$
  3. One random prize: 50$.

Contest format:

  • You will have to solve 7 tasks in 2 hours.
  • There will be full feedback throughout the entire contest.
  • Tasks will not have partial scoring, so you need to pass all test cases for a solution to count (ACM-ICPC-style).
  • Tasks will have dynamic scores. According to the number of users that solve a problem the score will vary between 100 and 1000.
  • Besides the score, each user will also get a penalty that is going to be used as a tie breaker.

About the penalty system:

  • Computed using the following formula: the minute of the last accepted solution + the penalty for each solved task. The penalty for a solved task is equal to log2 (no_of_submissions) * 5.
  • Solutions that don't compile or don't pass the example test cases are ignored.
  • Once you solve a task you can still resubmit. All the following solutions will be ignored for both the score and the penalty.

If you find any bugs please email us at contact@csacademy.com

Don't forget to like us on Facebook, VK and follow us on Twitter.

  • Vote: I like it
  • +76
  • Vote: I do not like it

Comments Comments (21)
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7 years ago, # |
  Vote: I like it -28 Vote: I do not like it

Wow. This is awesome. I can't wait to complete.

Is it CF rating? I WANT TO KNOW!

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    7 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    no, it is on another platform which is CS academy.

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7 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Just a remainder, contest will start in about 11 hours.

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7 years ago, # |
  Vote: I like it -32 Vote: I do not like it

Reminder, contest has started.

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

Will tasks be in sorted order by difficulty?

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7 years ago, # |
  Vote: I like it +60 Vote: I do not like it

ConStructAcademy

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7 years ago, # |
  Vote: I like it +47 Vote: I do not like it

Problem DEF are all constructive problems. Though interesting, I think it's way too much and I'm too stupid to work out all these problems :/

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7 years ago, # |
  Vote: I like it +1 Vote: I do not like it

How to solve E. How to prove, for every K answer is possible, Editorial is not clear to me https://csacademy.com/contest/round-43/task/coprime/statement/

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7 years ago, # |
  Vote: I like it +1 Vote: I do not like it

How to solve C? No editorial has been provided for it yet.

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

    Sort the stations in increasing order. Now for each interval bounded by two stations located at positions [a, b],  the expected distance the train will have to be pushed multiplied by b - a is equal to if b - a ≥ L or 0 otherwise.

    (Then we divide by D at the end to finish)

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      7 years ago, # ^ |
        Vote: I like it +10 Vote: I do not like it

      Did you miss a square?

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

      How did you get ((b-a-L)*(b-a-L))/4 ? I tried scratching my head but unable to figure it out

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

        Try graphing the needed distance to be pushed versus the position where the train stops. The total area between this curve and the x-axis is simply the sum of several triangles.

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      7 years ago, # ^ |
        Vote: I like it +5 Vote: I do not like it

      Sorry, but I think you forgot to divide by D.

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

editorial for E isn't clear to me? Can anyone explain their solution

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    7 years ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    I have made this YouTube Video for the editorial for problem E: Coprime Pairs.
    The solution link is mentioned in the video description.

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