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:
- First place: 100$
- Second place: 50$
- 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.
Wow. This is awesome. I can't wait to complete.
Is it CF rating? I WANT TO KNOW!
no, it is on another platform which is CS academy.
Just a remainder, contest will start in about 11 hours.
reminder, 90 minutes.
Reminder, contest has started.
Sir....You earned my Downvote. :P
Sorry I misslooked.
Will tasks be in sorted order by difficulty?
Yes
ConStructAcademy
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 :/
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/
How to solve C? No editorial has been provided for it yet.
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)
Did you miss a square?
How did you get ((b-a-L)*(b-a-L))/4 ? I tried scratching my head but unable to figure it out
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.
Got it. Thanks!
Sorry, but I think you forgot to divide by D.
editorial for E isn't clear to me? Can anyone explain their solution
I have made this YouTube Video for the editorial for problem E: Coprime Pairs.
The solution link is mentioned in the video description.