The 26th Central European Olympiad in Informatics will take place in Bratislava, Slovakia, during July 23rd-29th 2019. The most gifted high school students from 13 countries will have the opportunity to prove their knowledge and skills in informatics.
Codeforces will organise the online mirror for this year's competition. The online mirrors will take place after the finish of each of the 2 competition days, having the same scoring format.
The online mirror schedules are the following:
Contest format
- The contest will be unrated for all users.
- You will have to solve 3 tasks in 5 hours.
- There will be full feedback throughout the entire contest.
- The scoreboard will be hidden until the end of the contest.
- The tasks will have partial scoring. The maximum score for each problem will be 100 points.
- Among multiple submissions only the one that achieves the maximum score is counted towards the final ranking.
- The submission time does not matter for ranking.
- There will be enough fun for all colours ranging from newbie to international grandmaster. Legendary grandmasters can spice it up by turning it into a drinking game (ask Radewoosh for details).
Link to onsite contest with official rules and scoreboard
UPDATE: Much nicer scoreboard than on the first day made by arsijo. Many thanks!
Congratulations to all onsite contestants who battled our unusually hard problemset for 10 hours. You can view the final standings.
Many thanks to KAN for running the mirror, MikeMirzayanov for both platforms, all of our authors, testers and the whole CEOI staff and sponsors!
Day 1 mirror:
Day 2 mirror:
Results of both days combined: (https://codeforces.com/spectator/ranklist/e354b9b95c3626a3cfdfdb9eb37a7a6f)
Auto comment: topic has been updated by majk (previous revision, new revision, compare).
Heads up: the mirror of the second contest overlaps with Facebook Hacker Cup Round 3.
Funnily enough, this is not the first contest I tried to schedule in conflict with FBHC. Therefore, we move it to Sunday at 08:05 UTC.
also the same day we have ,google kickstart round. it will be really good ,if date can be changed but i know its not possible.
Radewoosh, please some words about drinking game
Radewoosh drinking game is such high iq. From Legendary Grand Master to Drunken Master.
Having the scoreboard hidden until the end is an interesting twist.
Where can I find the list of tests used for problems from past contests, if I'm solving the problem after the contest is over? For example if my submission is failing at Test 5, I want to know the data in Test 5 so I can troubleshoot.
Never mind, found it!
In case anyone else wants to know, you go on your profile page, and click Submissions, then click on the 8-digit number of your submission in the first column.
Can we solve problems and get score if we participate? Or it will be too hard?
Sorry for bad English!
You can. There are subtasks.
So where can we find said scoreboard?
Scoreboard
Thanks!
One more question: why does Romania use Russian flag in the scoreboard?
Just a prank bro.
You should be glad Romania, Czech Republic and Croatia don't have the Hungarian flag and Poland doesn't have a three-way mix.
I don't think this is funny. Contestants represent their countries. I, personally, would be quite offended if someone put another country's flag next to my name.
It was actually a typo and it was fixed pretty early on. If you can see it right now, there's something wrong with your cache or something.
I have no idea why people take me seriously.
Where is that profile picture from?
Do participants at CEOI have hidden scoreboard during the contest too? If no, maybe it would be better to also not hide the scoreboard at mirror contest?
They shouldn't have a scoreboard, and they shouldn't have internet access either. The mirror contest will have a public scoreboard because it doesn't matter and there's already a public scoreboard.
But mirror would also be more interesting without public scoreboard.
If you prefer it that way, you can simply not look at it during the contest.
Could someone tell me what's the difficulty of CEOI?
hard.
normal.
There are subtasks. Some are hard, some are easy. Some years (like the last 2), nothing is too hard. Other times, like this year, there's something hard and a lot of easy subtasks.
Could you also publish the contest material (tests etc.) after each contest day?
Yeah. After the mirror.
Whether the editorial of problems will be published?
Yes.
So good!
Why doesn't each subtask contain each previous subtask which it supersedes? For example, it shouldn't be possible for me to solve subtask 4 and not subtask 3 of A or subtask 2 but not subtask 1 of C. :|
Same problem with B, managed to solve subtasks 3,5,6 but not 1,2,4.
So it's possible to get 100 with the wrong solution by doing some not much good looking ifs.
My solution is still based on HLD ;D
Wait a minute, 6 is the full solution, how come you solve it and not solve 1, 2, 4!? I solved 1-4, but not 5-6. 5 is also not hard, but I didn't manage to write it.
I'd also prefer that, but it's not done at CEOI. Maybe to not overkill the kids. Therefore, that's how it is in the mirror too.
There is no need to tell the participants that this is done. They can assume the tests are copied into all suitable groups.
It's the truth, so I don't mind.
It is not always the case that subtask n+1 is the same as subtask n with some additional observations, so the dependencies would have to form a dag and we would need to give you that dag. I am sceptical whether such complication adds anything to the contest. If you managed to get subtask 2 for C but not subtask 1, this sounds more like weak tests then anything else.
You can also determine for each test case a subset of subtasks where it belongs to, and this can be done automatically using input validators. I think this is the optimal way to create subtasks in an IOI-style contest.
I have participated in an IOI type competition in first time and surprised at the very unusual format of this competition, in which the standings of the participants and the number of solved tasks are not visible. I also habitually tried to solve whole problem
How to solve the Dynamic Diameter problem? It looks very interesting.
It's quite similar to this task.
How to solve A ?
Editorial is here: /blog/entry/68676
Where can we see the CF scoreboard for the contest?
Where can I see the Final standings of this mirror?
Sorry, I thought it is opened automatically after the end. You can see the standings now.
Thanks
My solution for A:
Consider all buildings already built and that you are removing them one by one. Let V be number of vertices which are in contact with atleast one building, let E be number of edges which are in contact with atleast one building, now if the graph of building is connected, then Euler's formula for connected planar graphs must hold (here number of faces F = number of buildings + 1). So, you can only erase a building if erasing it will maintain the equality (the graph will remain connected), call such a building available. A building is on the boundary if it is contact with one empty space. Now, maintain a set of all buildings on the boundary which are available, and erase the one with maximum id. Update the set after erasing each building. (Each update will change the status of atmost 8 buildings so this can be done fast).
not sure, but seems correct.
Why should F be the number of buildings + 1? For example, the case of a 3x3 with a hole in the middle has 8 buildings, 10 faces and is connected.
I thought those cases would give "NO" output due to some reason. I was wrong. Thanks.
Can you please enable viewing other's submissions?
Vote you up. It seems that this feature is still to-be-done because of the special rule on these CEOI problems that CodeForces has never dealt with.
Meh, done. Viewing submissions was actually allowed, if you found them elsewhere, it was "viewing of common Status" that was blocked in the admin settings.
Anybody knows what happened to xyz111 (Yinzhan Xu) ? I can't see him on the top rated. Did his account get banned ? xyz111 p/s : I am a fan of him. lol ^^
Ranking applies only to handles that have participated in at least one contest in the last 6 months.
The Ukrainian delegation has prepared unofficial standings. The link is ce.oi.in.ua
UPD. If you don't see flags, please clear your cache.
can i see the CF scoreboard for the contest?
At CEOI are interesting problems, but the bad is that CEOI is all about speed. there are only five hours! It is impossible to solve this hard problems in 5 hours. I time will be more, I am sure I will solve all the problems. Do you agree me?
5 hours is like the maximum reasonable time. The problems are balanced in a way so only some people will be able to solve them in that time frame. Others will get less points.
I was a participant on-site. Honestly guys don't join it. It literally was the worst contest i ever saw.
Hey! No spoilers!
Good job on gold medal (Aia-i :))
Only 8 days left until international olympiad in informatic. This a good challenge before IOI Azerbaijan
I agree with you
At CEOI are interesting problems, but the bad is that CEOI is all about speed. there are only five hours! It is impossible to solve this hard problems in 5 hours. I time will be more, I am sure I will solve all the problems.
At CEOI are interesting problems, but the bad is that CEOI is all about speed. there are only five hours! It is impossible to solve this hard problems in 5 hours. I time will be more, I am sure I will solve all the problems.
Are you agree to my this think?
Yes, you would solve all the problems if the contest duration was 10 years
It's really anything but speed. If you can't solve these tasks in 5 hours, you can't in 10 years. They should be difficult for people participating at CEOI (top 4 in each country), so you shouldn't complain about their difficulty, nor should I.
Standings?
Are you going to combine both standings for CF mirrors?(maybe also virtuals too)
Done, see the link in the post.
How did you combine them?
KAN would be the right person to answer.
"Spectator ranklists" on ADM. page of any contest. I haven't tested it though, MikeMirzayanov made it for CEOI.
Is it possible to check submission running time in such type of contests?
If it's not then it would be great to add such feature.
MikeMirzayanov?
You can actually see your running time in the submission tab in your profile. So I guess it shouldn't be hard for the CF team to add it to other more common places.