csacademy's blog

By csacademy, 6 months ago, In English,

Hello, Codeforces!

We are going to host a new contest at csacademy.com. Round #74 will take place on Wednesday, March/28/2018 15:05 (UTC). This round will be a Div. 2, affecting users with a rating below 1800.

Facebook event

Recently, Facebook has reintroduced the possibility of recurring events. If you choose "Interested" here, you will be notified before each round we organise from now on.

Contest format:

  • You will have to solve 5 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.

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  • Vote: I like it  
  • +26
  • Vote: I do not like it  

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6 months ago, # |
Rev. 2   Vote: I like it +14 Vote: I do not like it

The round won't be held today. We're expecting you next week :).

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6 months ago, # |
  Vote: I like it +10 Vote: I do not like it

I think you had to announce it earlier :(

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6 months ago, # |
  Vote: I like it +17 Vote: I do not like it

Just a reminder. The contest will take place tomorrow.

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6 months ago, # |
  Vote: I like it +9 Vote: I do not like it

wefgef: Just a reminder, the round starts in 1 hour.

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6 months ago, # |
  Vote: I like it +6 Vote: I do not like it

Why did it start one hour earlier than declared in announcement?

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    6 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I received an e-mail claiming the round was to be held at 15:05 UTC. To my surprise, one contest hour had already passed when I was getting ready to participate :(

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      6 months ago, # ^ |
        Vote: I like it +9 Vote: I do not like it

      We're sorry about that. We had some the summer hour change in Romania and usually it messes things up.

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6 months ago, # |
  Vote: I like it +5 Vote: I do not like it

Are rounds the same time/day each week? I am interested but unfortunately this is not a great time for me.

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    6 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Yes. The time may change by a few hours based on how countries adapt to the summer time, but it's always on wednesday.

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6 months ago, # |
  Vote: I like it 0 Vote: I do not like it

In question Two Squares, why does the simple greedy approach not work?

During the contest, I came up with a solution in which I was first choosing the subsquare of size K containing the maximum number of 1's. Afterward, converting each cell to 0 inside the subsquare. Again, I repeated the same process on the newly generated matrix. I got WA for this approach. Can anybody explain me, what is the flaw with this concept?

Submission Link