majk's blog

By majk, 3 months ago, In English,

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:

  1. mnbvmar 300
  2. Benq 300
  3. gamegame 281
  4. ainta 271
  5. __.__ 254

Day 2 mirror:

  1. zx2003 230
  2. saba2000 230
  3. TLE 200
  4. cuizhuyefei 200
  5. panole 200
  6. dacin21 200

Results of both days combined: (https://codeforces.com/spectator/ranklist/e354b9b95c3626a3cfdfdb9eb37a7a6f)

Editorials: day1 day2

 
 
 
 
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3 months ago, # |
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Auto comment: topic has been updated by majk (previous revision, new revision, compare).

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3 months ago, # |
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Heads up: the mirror of the second contest overlaps with Facebook Hacker Cup Round 3.

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    3 months ago, # ^ |
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    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.

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    3 months ago, # ^ |
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    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.

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3 months ago, # |
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Radewoosh, please some words about drinking game

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3 months ago, # |
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Radewoosh drinking game is such high iq. From Legendary Grand Master to Drunken Master.

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3 months ago, # |
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Having the scoreboard hidden until the end is an interesting twist.

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3 months ago, # |
Rev. 4   Vote: I like it 0 Vote: I do not like it

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.

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    3 months ago, # ^ |
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    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.

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3 months ago, # |
Rev. 2   Vote: I like it +8 Vote: I do not like it

Can we solve problems and get score if we participate? Or it will be too hard?

Sorry for bad English!

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3 months ago, # |
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So where can we find said scoreboard?

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    3 months ago, # ^ |
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      3 months ago, # ^ |
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      Thanks!

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      3 months ago, # ^ |
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      One more question: why does Romania use Russian flag in the scoreboard?

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        3 months ago, # ^ |
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        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.

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          3 months ago, # ^ |
          Rev. 2   Vote: I like it +54 Vote: I do not like it

          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.

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    3 months ago, # ^ |
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    Where is that profile picture from?

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3 months ago, # |
  Vote: I like it +3 Vote: I do not like it

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?

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    3 months ago, # ^ |
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    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.

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      3 months ago, # ^ |
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      But mirror would also be more interesting without public scoreboard.

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        3 months ago, # ^ |
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        If you prefer it that way, you can simply not look at it during the contest.

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3 months ago, # |
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Could someone tell me what's the difficulty of CEOI?

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    3 months ago, # ^ |
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    hard.

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    3 months ago, # ^ |
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    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.

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3 months ago, # |
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Could you also publish the contest material (tests etc.) after each contest day?

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3 months ago, # |
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Whether the editorial of problems will be published?

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3 months ago, # |
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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. :|

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    3 months ago, # ^ |
    Rev. 2   Vote: I like it +8 Vote: I do not like it

    Same problem with B, managed to solve subtasks 3,5,6 but not 1,2,4.

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      3 months ago, # ^ |
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      So it's possible to get 100 with the wrong solution by doing some not much good looking ifs.

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        3 months ago, # ^ |
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        My solution is still based on HLD ;D

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      3 months ago, # ^ |
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      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.

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    3 months ago, # ^ |
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    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.

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      3 months ago, # ^ |
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      There is no need to tell the participants that this is done. They can assume the tests are copied into all suitable groups.

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        3 months ago, # ^ |
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        It's the truth, so I don't mind.

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    3 months ago, # ^ |
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    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.

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      3 months ago, # ^ |
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      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.

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3 months ago, # |
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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

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3 months ago, # |
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How to solve the Dynamic Diameter problem? It looks very interesting.

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3 months ago, # |
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How to solve A ?

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3 months ago, # |
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Where can we see the CF scoreboard for the contest?

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3 months ago, # |
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Where can I see the Final standings of this mirror?

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    3 months ago, # ^ |
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    Sorry, I thought it is opened automatically after the end. You can see the standings now.

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3 months ago, # |
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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).

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    3 months ago, # ^ |
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    not sure, but seems correct.

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    3 months ago, # ^ |
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    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.

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      3 months ago, # ^ |
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      I thought those cases would give "NO" output due to some reason. I was wrong. Thanks.

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3 months ago, # |
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Sir ,when will Editorial ,will be published ?

,I found test cases to be very tough ,in first question i made almost 12+ submission , every time a single test case failed in every sub task . Hence results in zero . Also can we have access to test cases used in problems .

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3 months ago, # |
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Can you please enable viewing other's submissions?

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    3 months ago, # ^ |
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    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.

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    3 months ago, # ^ |
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    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.

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3 months ago, # |
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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 ^^

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3 months ago, # |
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****I LOVE PROGRAMMING*****

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3 months ago, # |
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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.

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3 months ago, # |
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can i see the CF scoreboard for the contest?

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    3 months ago, # ^ |
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    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?

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      3 months ago, # ^ |
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      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.

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3 months ago, # |
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I was a participant on-site. Honestly guys don't join it. It literally was the worst contest i ever saw.

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3 months ago, # |
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Only 8 days left until international olympiad in informatic. This a good challenge before IOI Azerbaijan

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3 months ago, # |
  Vote: I like it -33 Vote: I do not like it

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.

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3 months ago, # |
  Vote: I like it -40 Vote: I do not like it

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.

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    3 months ago, # ^ |
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    Are you agree to my this think?

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    3 months ago, # ^ |
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    Yes, you would solve all the problems if the contest duration was 10 years

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    3 months ago, # ^ |
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    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.

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3 months ago, # |
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Standings?

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3 months ago, # |
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Are you going to combine both standings for CF mirrors?(maybe also virtuals too)

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    3 months ago, # ^ |
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    Done, see the link in the post.

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      3 months ago, # ^ |
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      How did you combine them?

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        3 months ago, # ^ |
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        KAN would be the right person to answer.

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        3 months ago, # ^ |
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        "Spectator ranklists" on ADM. page of any contest. I haven't tested it though, MikeMirzayanov made it for CEOI.

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2 months ago, # |
  Vote: I like it +16 Vote: I do not like it

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.