jonathanirvings's blog

Invitation to TOKI OSN Open Contest 2019
By jonathanirvings, history, 5 years ago, In English

Hello!

Similar to last year, we are excited to invite you to TOKI OSN Open Contest 2019 -- an online mirror contest for Indonesia national olympiad in informatics. This national olympiad is one of the stages required for our students to qualify to represent Indonesia in the International Olympiad in Informatics (IOI).

The contest is similar to IOI: 2 competition days (+ 1 trial session), each consisting of 3 IOI-style (partial, subtasked) problems to be solved in 5 hours. The schedule is as follows:

Each contestant can select any 5-hour window within the time range to do the contest for each competition day. Each contestant may start the contest any time within the time range, by clicking a provided timer button.

All three contests are now available on TLX. Please register in those contests. You may need to register for a TLX account if you do not have one.

For more detailed information and rules, see our official website.

See you in the leaderboard! :)

UPD1: The contest is over, thanks for participating. We are still working on the post-contest blog summarizing the contest, including the problem repository and credits. Meanwhile, the scoreboard for TOKI OSN Open Contest 2019 is available here. The problems are also available for upsolving here (TLX account is required).

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Comments Comments (16)
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5 years ago, # |
  Vote: I like it +16 Vote: I do not like it

The first day contest will be available in less than an hour!

https://tlx.toki.id/contests/tooc-2019-day-1/

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

The second day contest will be available in less than an hour!

https://tlx.toki.id/contests/tooc-2019-day-2/

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5 years ago, # |
  Vote: I like it +5 Vote: I do not like it

How can we submit for practice?

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5 years ago, # |
  Vote: I like it +27 Vote: I do not like it

Is there any way to view the global results/ranking?

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

    Yes! the result will be announced on osn2019.toki.id on July, 7th 2019 11:00 UTC. Sorry for the delay.

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5 years ago, # |
  Vote: I like it +9 Vote: I do not like it

See you in the leaderboard! :) And we want to see that leaderboard :D

When will we be able to see the leaderboard?

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

    if you are one of contestant, you should be receiving an email. If not, you can see the scoreboard on July 7th, 11.00 UTC in this link https://osn2019.toki.id/

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

    What is your score?

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      5 years ago, # ^ |
        Vote: I like it +1 Vote: I do not like it

      $$$571$$$ points. $$$71$$$ from $$$day1-C$$$, $$$100$$$ from other problems. I am so much regretting not trying some approaches for $$$day1-C$$$ $$$:($$$

      What is your score?

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        5 years ago, # ^ |
        ← Rev. 2   Vote: I like it +8 Vote: I do not like it

        I got 565 points(100-100-83-100-100-82). I used DP for day1C.

        My solution

        This solution got 9 points in last three test cases.

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

    The leaderboard for TOKI OSN Open Contest 2019 is available in the UPD1 of the post :) Thanks for participating!

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

Is there one full solution for the output only task from the first day of contest? I got 84 points by analyzing different cases.

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    5 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    You can nuke the problem by using min-cut.

    Or actually, if you try to see which free cells can't be reached from start to end, surprisingly there are a lot (like ~90% even on the last testcase). So you can manually put optimal obstacles by hand.

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

    The judge solution contains three different implementations, all find the optimal solution in under one second:

    • One that solves C ≤ 16 using DP with broken profile (this covers rekreasi_{1..4}.in)
    • One that solves empty grid input (this covers rekreasi_{5..7}.in)
    • One that solves single turn input using shortest path (this covers rekreasi_{8..10}.in)

    Given that each test case constraint (the fact that each test case is either C ≤ 16, empty grid, or single turn) is clearly mentioned in the problem statement, we don't see our solution as heuristics. And yes, we are aware of the O(N^3) maxflow solution and acknowledged this as a possible alternative solution.

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