Bok!

I am delighted to invite you to a mirror of the Croatian Olympiad in Informatics!

As part of the COCI series, we are hosting an Internet online contest with problems from the Croatian Olympiad in Informatics 2024. The contest is primarily intended for high school contestants, but is open to all interested!

This contest is used in Croatia to select members of the IOI 2024 team. There will be three to five tasks and the contest will be five hours long. The contestants will have full feedback with at most 50 submissions per task.

The problems were set by dorijanlendvaj, keko37, Agnus, psruk and myself.

This year, we are trying something new! Instead of the usual 5-hour mirror format, we are adopting the new format where you are given 24 hours and you can start your own 5 hours whenever you like. Notice that if you start less than five hours before the end of the contest, your window will still be 5 hours long.

It will be held on Sunday, April 28, starting at 15:00 (GMT/UTC).

Check out your local times at https://hsin.hr/coci/next_contest.html.

You may use Python, Pascal, C, C++, or Java as your programming language of choice.

The two relevant websites are:

https://hsin.hr/coci/ — information about the contest

https://evaluator.hsin.hr/ — judging system

We hope that you will join us or encourage your students to do so!

Croatian Open Competition in Informatics — COCI 2022/2023

Internet online contest series

As part of the COCI series, we are hosting an Internet online contest with problems from the Croatian Olympiad in Informatics 2023. The contest is primarily intended for high school contestants, but is open to all interested!

This contest is used in Croatia to select members of the IOI 2023 team. There will be three to five tasks and the contest will be five hours long. The contestants will have full feedback with at most 50 submissions per task.

The problems were set by dorijanlendvaj, ipaljak, keko37 and myself.

It will be held on Sunday, May 21, starting at 15:30 (GMT/UTC).

We have been notified about the clash with the AtCoder round. The starting time has changed, the new starting time is the one above, the old one was 14:00 GMT/UTC.

Check out your local times at https://hsin.hr/coci/next_contest.html.

You may use Python, Pascal, C, C++ or Java as your programming language of choice.

The two relevant websites are:

https://hsin.hr/coci/ — information about the contest

https://evaluator.hsin.hr/ — judging system

We hope that you will join us or encourage your students to do so!

When we log in into the Yandex contest, we get the following message: "You are not allowed to view this contest"

Is anyone else having the same problem?

The competition is in 2 days and I still can't find a list of all the participants. So if you are a participant please write your team.

From Zagreb, Croatia dorijanlendvaj and I are here.

First of all, I want to congratulate everyone who won medals. Special congratulations to everyone who won gold medals. And special special congratulations to Egor.Lifar who won eJOI 2018 by solving all 3 problems on Day 2.

I myself won a silver medal and I would like to write about some things I did wrong at the contest.

Focusing too much on a single problem

Most of the time at Codeforces Rounds it is perfectly fine to concentrate on one problem because all the other problems you haven't solved yet. On an olympiad, you never quite know which problem is easy and which is hard. At this eJOI, the problems on both days were sorted by expected difficulty, but at least I wasn't notified it was going to be in that order.

Thinking you cannot solve a problem

Entering the contest hall on Day 2, I thought the problems would be harder than Day 1 and I didn't expect to solve any problem. So I didn't even try to solve the whole problem A on Day 2, and I was pretty satisfied when I got 75. Seeing the results, it turned out yes the problems was harder, but not unsolvable.

Finding the balance between the hardness of a subtask and the number of points it gets.

Day 2 included an output only problem. The number of points you will get on an output only problem is usually hard to predict. I thought that it was more useful to work on my output only solution than to try to code some more subtasks on Cycle sort which I already had in mind. I decided to work on my output only solution which turned out to be a mistake. I got only 4 or 5 points more than I already had. Half an hour before the end of the contest I started coding those subtasks on the last problem but there wasn't enough time left.

I would like to make it clear this is only my second Olympiad in informatics and these are only some of my thoughts. If you have any piece of advice or thoughts, they are more than welcome.

I couldn't find any good answers so I am posting here.

Currently, I know the splay tree data structure and I am thinking about learning treap. How useful is it to know Treap when you already know the splay tree data structure?

I am especially interested in finding an answer to these 4 questions:

Which do you find easier to code?

Are there any problems treap can solve and splay can't and vice versa?

Which is usually faster in practice?

And finally are there any other BBST you use except for the most popular splay tree and treap?

Ejoi has been announced to be held in Russia in 2018 at the end of Ejoi 2017, but still no official website has been made and neither an official announcement as far as I found. Does anybody know anything about the date of the Olympiad and has there been any rule changing?