riadwaw's blog

Challenge24 EC
By riadwaw, 10 years ago, In English

Contest is over.

How to solve D ?

How to solve F correctly?

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10 years ago, # |
← Rev. 3   Vote: I like it +21 Vote: I do not like it

Is there any task in contest without huge problems with input/output/evaluation?

I spent almost 2 hours writing solutions to debug A4 :|

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

    Yes, B.

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

    What is the thing between A4?

    I'm almost sure that my algo works but it kept failing on that test case

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10 years ago, # |
  Vote: I like it +115 Vote: I do not like it

Looks like the organizers had too much fun counting popcorn and forgot to prepare the rest.

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10 years ago, # |
  Vote: I like it +26 Vote: I do not like it

F is easy — just BFS. The only trouble is implementation (and conversion from their shitty coordinates to some normal ones).

They really need some proper UI to notify users about ongoing issues. Current approach with "Announcements" is horrible, thanks to it we've spent enormous amount of time debugging A and C without noticing that these problems are bugged :( There were just two of us participating today, so it effectively blocked the whole team for significant period of time.

Btw, what are your scores? Since leaderboard will be published with some delay, I guess it makes sense to share scores here. Our final score is 2404.

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

    I send bfs too in F, but we didn't manage to get the answer in 7 and send -1 randomly and in 10 we had to add some restrictions like abs(x) < 100, abs(y) < 100, v < 15 or something.

    Our current score 2624, but we don't know if get more/less points on E.

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

1) Yesterday it was stated that the contest will last for 6 hours. But now suddenly, it ends after 5 hours, ruining submission and solving plan totally, making me hate the contest for that

2) Team spent so much time on debugging correct solution of A, that had not enough time for other problems

I don't know how usually Challenge24 contests are prepared and held, but this one was bad

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

My answer for the third test case in the sample of C was "NO", but the solution is accepted. Is it OK? :)

Our score is 2337.

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    10 years ago, # ^ |
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    Same here. I guess there wasn't any more inputs with all the given coordinates equal to each other.

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10 years ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

I spent so much time in E & got so little score. For E1, I got some positive score at some point, and after that always get 0. I even tried resubmit previous output but still got 0. Anyone had same issue? Now I only have E2 & E4 :( not sure what will happen after rejudge..

Then, I tried estimating + random guessing for B. I think I got around 360 for that. How to solve it better?

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

    We have the same issue, we resubmitted the same output in E1 and got 0 instead of 8 or something

    Our output is in previous revision

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    10 years ago, # ^ |
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    Then, I tried estimating + random guessing for B. I think I got around 360 for that. How to solve it better?

    You can't really do anything better. At first I tried to count them properly, but this was lower by 10-20%. IMHO, it was just a roulette. I believe I got somewhat lucky and I have 641 (after deducting penalties).

    Pretty much all of the tasks were broken which is really sad, considering how awesome EC was last year.

    Our "current" total score is 3553 (we didn't get the "D"). And we're hoping that they will correct rejudge E. So far we 100's for E1, E2 & E4. But we also submitted others (except for E5) and at least E3 should be correct (and optimal).

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

      what is your output in E1 ?

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      10 years ago, # ^ |
      ← Rev. 2   Vote: I like it +21 Vote: I do not like it

      jablko's solution for B: 

      int n = some_low_guess;
while(submit(n) == "WA")
{
  n *= 1.3;
}

      UPD: Our displayed score has changed to 2229, for some unknown reason.

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

        Because problem E was rejudged.

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

How to spend time solving D:

  1. Submit d1
  2. Receive "Internal Error"
  3. Wait 20 minutes
  4. "Now talking in #d
    NIN: When will our d1 be re-evaluated?
    @Igor2_not_org: hmm, did i miss something, why should it be reeval'd?
    NIN: our submit had status "Internal Error, will be reevaluated
    ...
    @Csirke: NIN: Checking
    @Csirke: NIN: eval should be fixed now"
  5. ????
  6. PROFIT!!!
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10 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Results are published. It seems that E was not fully rejudged

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

What is solution for A?

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    10 years ago, # ^ |
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    My approach:

    Notice there aren't many sequences (10). Also, maximum length is about 6000 and there aren't that many distinct values ~1500, I think.

    Use the smallest sequence as reference. LCS must be contained in that one. Remove all values from other sequences that contain values not in the smallest sequence. This shrinks the sequences even more.

    Then use dynamic programming where the state is a vector of the current available numbers in each sequence. Pick a number on the smallest sequence and check if it appears in all other sequences.

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10 years ago, # |
  Vote: I like it +11 Vote: I do not like it

This contest goes for the first time?

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

Pretty sad that the contest had so many errors, after waking up early in a saturday morning excited to participate.

I didn't participate last year, but heard the contest was pretty good. I didn't like most problem statements, especially D: not well explained, lacking samples or a pain (on purpose) [F].

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10 years ago, # |
  Vote: I like it +83 Vote: I do not like it

Information from the main page of the competition:
"Due to organizing difficulties probably we postpone the finals to end of June. We try to do our best."

I recommend to wait for an update before buying tickets to the finals :)

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10 years ago, # |
  Vote: I like it +29 Vote: I do not like it

It's now March 9th — has anyone heard any new news about the finals?

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10 years ago, # |
  Vote: I like it +10 Vote: I do not like it

We are awfully sorry to inform you that due to technical difficulties Finals of 15th Challenge24 has to be postponed between 26th and 28th of June. Detailed information coming soon (around 15th March).

Thank you for your understanding!

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10 years ago, # |
← Rev. 2   Vote: I like it +16 Vote: I do not like it

Does anyone know when can we expect to see detailed information about Finals? It's 28th March now and orgs said that it would be around 15th March...

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9 years ago, # |
← Rev. 2   Vote: I like it +21 Vote: I do not like it

Is there any chance that someone who currently in Budapest don't have a team and want to participate? Our teammate cheshire_cat is not able to attend, but me and mastersobg are here and we urgently need someone to complete a team. [still relevant]

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