Привет, Codeforces!
Мы рады пригласить вас поучаствовать в нашем раунде TheForces Round #4 (EZForces), который пройдёт во 17.01.2023 18:05 (Московское время)!
Пожалуйста, не забудьте время!!!
Вам будет дано 7 задач и 2 часа на их решение
Наша команда состоит из 4 человек: E404_Not_Found, k1r1t0, psychobot, O--O
- Задачи были подготовлены O--O и E404_Not_Found
- Кроме того, спасибо k1r1t0, chromate00, Psychotic_D за тестирование раунда
- Снова спасисбо k1r1t0 за помощь в исправлении условия задачи D
- psychobot не было в нашем чате, мы надеемся все хорошо...
Мы уверены что вам понравится раунд!
Поздравляем победителей!!!
I like this kind of contests.
As tester, i dont have anything to say about problems, they are nice i think
As a tester, I think they are great, and rejudging after the contest will give a realistic experience.
When will the final result be published?
Is it kind of a div 4 round ? O--O
You can see other contests in my blogs. It is not div 4 round. But some problems are suitable for beginners. Different difficulty problems.
I loves your contests very much it is really great<3.
Will be rated?
Is it rated?
Weak pretests and no hacks. What's the point?
You can hack after the round, but it's only available for candidate master+ people because of Codeforces limits, Also the point is to make mashups closer to the Official rounds.
Don't worry bro, You can hack after the contest end.
is it rated ?
No bro it's unofficial mashup round
Why have you hold 3 contests, but the number of the contest is # 4?
Hi, you can see first 3 contests in my blogs.
Contest starts...
Delayed by 5mins?
Contest started !
please open the others solutions or make tutorial blog for this contest.
I find sequence in the problem E from OEIS, and easily solved this problem :)
What is the intended time complexity for F and how to solve D?
It's $$$O(n)$$$ for F.
D: Ternary search over the touching point.
D can be done in O(1)
Sure, but as for me ternary search comes to mind immediately.
Same
Just went through ur solution.
How is this O(n)?
Oh, sorry, I confused G with F. It's actually $$$O(n * \sqrt{C} / ln(C))$$$ in submission, not sure if it is intended.
To solve D you can notice that the shortest distance between 2 points is the line joining them, however you also need to touch the river atleast once, so think of a geometric transformation that sends one of Alice or Bob to the other side of the river and then see if you can come up with something.
Cool
There are two solutions for this problem, but the expected solution is like this:
Reverse (multiply by -1) the width of one of the points and get the Euclidean distance of the obtained point with the other point, It can be proven that the obtained distance is the shortest possible
It's strange, but for me ALL notifications during and after contest were "undefined" without any text and so on. I also have nothing in "questions" section. Thus 13th test of C was really evil
After all, I liked problems despite being them relatively easy for me (D was too old and I have seen it before hundreds of time)
We announced in English during the contest
I don't have any notifications (in dashboard) even if I switch locale to english one. I had only one proper notification about "only CM+ can hack". And I haven't switched language... Can it be codeforces bug? I have never had problem with notifications, even if my locale is russian and notification is in english (I think that majority of notifications are in english)
We did hide them
@O--O how i am get wrong answer after printing 1e9 instead of 1000000000 here is my submission link regreted code
You should print integer, not double.
but why double was wrong both gives the same output , for n =1 my submitted code printed 1000000000 in my ide :(
For G, we can tell that the answer is $$$(n+1)(n + 1 - H_{n+1})$$$. Since we don't need to be very accurate, there's a solution in $$$O(1)$$$ where use $$$H_{n+1} \approx ln(n+1) + \gamma$$$
Submission
Oh hey, yes I did point this out during the testing, but we decided not to make it too hard and kept the task to $$$O(n)$$$. IIRC, a similar technique is used on "Increasing Sequence Card Game" from Kick Start 2021.
How can I hack a solution ?
only candidate master+ can hack.
Auto comment: topic has been updated by O--O (previous revision, new revision, compare).