ipaljak's blog

Croatian Olympiad in Informatics (COI) 2020
By ipaljak, history, 4 years ago, In English

Hi all,

Croatian Olympiad in Informatics (COI) represents the first major step towards forming the Croatian IOI team. As you know, we usually hold an online mirror of this contest as the last round of the COCI season. Since this year is already unusual, we decided it was ok to postpone the online version of the contest until we have a (hopefully) stable version of the new judging system.

On that note, I'm happy to invite you to join us on Saturday, October 3, starting at 15:00 (GMT/UTC). The contest will feature 4 IOI-style tasks and it will last for 5 hours. You will also have full feedback with at most 50 submissions per task.

You can access the judging system here. The registration period ends 1 hour before the beginning of the contest (look it up under "Events"). If you wish to get a bit more familiar with the system, we have uploaded the last 14 COCI seasons for you to practice on. Most problems (except for the very easy ones) have English translations. Also, some custom checkers have been lost during the years so some problems might be wrongly judged, we will fix that along the way. In general, the more recent the season, the greater chance for the checkers to be correct. This judge will be used for the next COCI season.

The tasks were prepared by: tonkosi, abeker, paula, dpaleka, Shtef, ipaljak and mkisic.

Hope you'll enjoy the contest.

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Comments Comments (18)
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4 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Auto comment: topic has been updated by ipaljak (previous revision, new revision, compare).

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4 years ago, # |
← Rev. 2   Vote: I like it -11 Vote: I do not like it

authors is the round rated for pupils like me.ipaljak

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    4 years ago, # ^ |
      Vote: I like it +18 Vote: I do not like it

    The contest is not rated and we don't intend to implement any sort of rating feature in the near future.

    If you wish to get a feeling for the general difficulty of the problems, it's probably best for you to take a look at the last couple of years (2018/2019, 2017/2018).

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4 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

There is an ARC on atcoder on the same date which starts 2hours before COI.right now the duration is saying 100 minutes(default value) but most of the time it is changed to 150minutes later so it may clash.Can you please prepone or postpone this to some other day?.Even if it doesn't clash doing 7+ hours of continuous contests seriously is very hard and I think participation may decrease a lot.thanks

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    4 years ago, # ^ |
      Vote: I like it +28 Vote: I do not like it

    We have another local event on October 6th (postponed nationals due to COVID) and the technical team is not comfortable having this any later than October 3rd. On the other hand, we also don't have enough manpower during working days, so I'm afraid we're stuck with the date.

    That being said, we will consider postponing COI for an hour or two. I'll keep you posted.

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

The time and date points to 5 April 2020, 14:00 UTC. Can you please fix it?

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    4 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Fixed, thanks.

    You might need to clear your browser cache to see it though.

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4 years ago, # |
  Vote: I like it +81 Vote: I do not like it

Participating in this contest boosted performance of Croats by 10000%. This literally the best possible preparation for IOI or life in generals so please participate!!!!!!

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4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Auto comment: topic has been updated by ipaljak (previous revision, new revision, compare).

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4 years ago, # |
  Vote: I like it +35 Vote: I do not like it

Due to the suggestion from kshitij_sodani, we've decided to postpone the contest for 1 hour. The starting time and registration time will soon be fixed accordingly on the judging system.

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4 years ago, # |
  Vote: I like it +51 Vote: I do not like it

Friendly reminder: the round starts in ~30 minutes.

We also extended the registration deadline, you can register until 10 minutes after the contest starts.

Good luck!

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4 years ago, # |
← Rev. 2   Vote: I like it +22 Vote: I do not like it

The contest is over, hope you had fun.

We will publish the editorial soon.

Also, we would like to gather any feedback regarding the experience with the new judge. From our side, everything seemed to be going smoothly. We have a list of (mostly UX related) issues that we plan to address but would love to hear your input on this as well.

EDIT:

The editorial is published.

You can also submit the tasks in our archive (look under tasks/srednje skole/2020/HIO)

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4 years ago, # |
  Vote: I like it +16 Vote: I do not like it

can anyone share how to do B?

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    4 years ago, # ^ |
    ← Rev. 2   Vote: I like it +24 Vote: I do not like it

    Root the tree, sort the sheep by depth, then you can prove that it's always optimal to protect the deepest unprotected sheep with the highest possible shepherd.

    This is straightforward to implement in O(N^2), you need some more observations for O(N log N) or O(N).

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4 years ago, # |
  Vote: I like it +13 Vote: I do not like it

You can see the scoreboard at https://evaluator.hsin.hr/events/coci20_7/scoreboard/. Congrats to the full scores, and thanks everyone for testing the platform for the new COCI season!

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4 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

can anyone please give the link to editorial?

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4 years ago, # |
  Vote: I like it +28 Vote: I do not like it

It's a bit late, but you can solve all problems here: https://oj.uz/problems/source/536

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