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Zlobober's blog

Yandex.Algorithm 2016 Finals
By Zlobober, 8 years ago, translation, In English

UPD2: Tomorrow (July 31st, Sunday) at UTC 10:00 there will be an online mirror of Yandex.Algorithm final round.

Enter contest.

Everybody are invited to participate! You may discuss problems in comments after the contest ends.

UPD3: The online mirror has finished! Congratulations to ImBarD aka Vercingetorix for taking the first place.

Problem editorial

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Hi everybody!

We're glad to remind you that tomorrow, July 29th, at 9:00 AM UTC there will be the Final Round of Yandex.Algorithm 2016 in Minsk. List of finalists and elimination stage results are available on Yandex.Algorithm website.



You can watch follow the news on final round at Yandex.Algorithm website. Want to solve final round problems? On Sunday, July 31st, at 10:00 AM UTC there will be a mirror of the competition. Everybody can participate in it, solve the same problems as finalists and try his or her best on the finals' problemset.

The final round has been prepared by authors of previous stages of Yandex.Algorithm: Endagorion, Romka, Chmel_Tolstiy, GlebsHP, snarknews, Gassa and your humble servant. We believe that problems are various and interesting.

In this post after the cut I'll write some comments about what happens in the contest trying not to spoil any important details (we don't want to provde help or to ruin contest for any of the participants, isn't it?).

See you tomorrow!

UPD:

Congratulations to the winners!

  1. Egor winning 300 thousands of rubles.
  2. W4yneb0t winning 150 thousands of rubles.
  3. rng_58 winning 90 thousands of rubles.

Final results are available here. The competition is finished, everybody are invited to participate an online mirror on Sunday!



-0:25: Competitors have already set up their laptops and are waiting for the competition to start. There are six finalists participating onsite this year: Errichto, Egor, eatmore, tourist, vepifanov, aid. Also there are some guests from Belarus, in particular Belarus national team for IOI 2016.

-0:10: Here are great prizes the competitors will fight for.

0:00 The Finals has started! There are six problems that are shuffled (i. e. do not follow in the order of difficulty).

0:07 Participants start coding. I'm going to tell a bit about problems they are trying to solve (when it happens).

0:25 Contestants opened problems C, B (in blind), A and F very fast: the first to solve problem C was taken by Um_nik and this is the most popular problem at this moment. It is about swapping people in order to make them seat in a certain manner. Looks like it will be an easiest problem to solve.

0:39 Problem A is very unusual: it looks like a graph problem, but the graph is fixed and does not depend of the input data. Also it is related to the beatuiful National Library of Belarus where the competition is held:

There are currently two contestants in the top with three problems, but there is also eatmore who has two problems, but both of them are submitted in blind mode.

0:48 Problems B and F both seem to be easy, but standings show that they are trickier then it looks like. Success rate (considering only open submissions) for both of them is lower than 50%.

1:00 There are only 40 minutes left. Egor takes the lead with four "easier" (according to statistics, of course) problems. There is also Errichto who submitted problem E in blind mode. If he succeeds to solve an "easy" problem F and a "medium" problem A, he will take the lead.

1:25 It is only 15 minutes till the end of the contest and still no submissions for problem D. Looks like all the leaders with 4 problems are working on the problem E inspired by Errichto's blind submission. Though, I don't actually know that :)

1:40+ The competition is finished. The final results are available here

  • Vote: I like it
  • +189
  • Vote: I do not like it

Comments Comments (29)
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8 years ago, # |
  Vote: I like it +6 Vote: I do not like it

the online mirror will be at codeforces???

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

    No, it will be on contest.yandex.com as well as all official rounds. Detailed information about the mirror will be added tomorrow or on Saturday.

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

Will there be a scoreboard for spectators? I hope so :D

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8 years ago, # |
  Vote: I like it +22 Vote: I do not like it

When will you finalize the standings?

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

Can anybody share unfrozen results from onsite?

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8 years ago, # |
← Rev. 2   Vote: I like it +76 Vote: I do not like it

We kindly ask you not to discuss the problems in public until 11:40 UTC, Sunday.

Мы просим вас не обсуждать задачи и решения публично до 14:40 UTC+3 ближайшего воскресенья.

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8 years ago, # |
  Vote: I like it +21 Vote: I do not like it

Up on this. Round starts in an hour.

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

Nice problems — except F, which is full of small catches (three WAs because of identical fractions...).

My solution on B is moving to sums of adjacent elements, which can only give 8 differently behaving things, ignoring zero sums and considering their position mod 2. Then, we can remove 2 non-zero sums in 1 move, 3 in 2 moves or 1 in 1 move.

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

    what was your idea for C

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

    What's the meaning of moving to sums of adjacent elements?Can you give an example?

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

Enjoyed the problemset, although I felt bad using OEIS for A :(

to Zlobober: I am ImBarD

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

    Congratulations :)

    Before the contest I checked if the results are googlable and even entered the sequence in OEIS but looks like I screwed somewhere, because I didn't find this solution. Fortunately, at Finals almost nobody used it.

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

      Is there a editorial for the problems?

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

        Yes, there is now a link to the editorial in the post. Sorry for the delay.

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

    LOL. It's funny that I used OEIS to get the 12th Bell number, but I didn't even think about using it to solve this problem.

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

BTW, in task A it was possible to calculate the chromatic polynomial of graph (by recurrence relation).

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

    For A,clearly it's symmetry, we can enumerate the 8 middle squares,then enumerate the 4 upside squares.

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8 years ago, # |
← Rev. 2   Vote: I like it +10 Vote: I do not like it

Meh. I am currently participating virtually, but I can't submit anything, because "Contest is not over. Upsolving is unavailable." — great fun xd.

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

    OK, so what do I do with this ; p? (After virtual participation ended I was finally able to submit my solutions xD)

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

      I believe it is a temporary issue for all contests in Yandex.Contest right now. I've notified people responsible for it, wait for updates.

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

I am yet to get my t-shirt. I remember entering my address in the form sent to me. Are we suppose to get our t-shirts by now or is it still in progress?

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

    It's in progress, stay tuned! Message me in yandex.contest feedback form to get more accurate information

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

      Thanks for your quick response. I am not able to submit the feedback for some reason. It's asking me to login even though I am logged in. And nothing happens when I click the log in link.

      http://imgur.com/a/dtXj1

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