They have started 8 minutes ago. Don't know much about the mirror, isn't it 1 hour after the competition start?

The mirror contest is now available at Yandex.

Breathe deeply, be strong, wait for mirror, be strong...

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Yesterday I also realized that the distribution of this problem is not good (only 20, 90-100 assuming most people got subtask 1, which is relatively easy). During the yesterday's GA meeting, I raised a minor objection about this. However, the answer from the ISC is satisfying (believe me), so now I am agree with the scoring :)

Do you have any ideas about that problem?

lol I quickly found out all other teams, but wondered which team is the hydralisk

пожалуйста, не игнорируйте объявления жюри, задача prize is under construction

MASSIVE CONGRATULATIONS yutaka1999!! Winning both IMO and IOI , impressive... Is he second person in history to achieve this, after Reid Barton as far as I remember?

Congratulations, nice double win!

Let's go to major international tournaments together next year and compete for the titles :)

Thanks for info!

Now they're saying "by at least 15 minutes, maybe longer".

Граница бронзы — минимальный результат что медали получают не больше половины участников.

Did they give any reasons for the extension?

Are the contestants able to submit solutions in the extended time? (I hear Achilles chasing a turtle...)

http://ioi2017.snarknews.info/index.cgi?data=2017/day1pre&class=ioi2017&year=2017

Panic :D

Thanks god
I almost thought they are going to make day 3

The scoreboard hasn't changed yet.

Do we have to wait until the closing ceremony to see the results?

1) There's a lot of least valuable boxes and just a few of more valuable ones
2) Try determining at least one
3) If we have two of them, how can we tell whether there is more valuable one between them? How to use this fact to look for more valuable boxes?

Simple solution for 90 points.

It's easy to see that at most 500 items are non-lollipops. So query the first min(n, 500) items to find at least one lollipop (this is the one with largest answer sum).

Then to locate all the non-lollipop boxes we could binary search prefixes; it takes at most 500*log_2(200K) ~ 8.5K. (you could save a bit, not sure how many by memoizing queries)

Afterwards just search each of the non-lollipop one by one for the diamond (there's at most 500 of them); the diamond is the one with both 0 result.

to reduce queries from to , divide the array into blocks and then binary search just within each block.

yutaka seems better for me :p
but I wonder what is inside the brackets ?

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sad as fuck. how else can i feel

Give them a break, man.

Hi, i was kinda frustrated, now i'm much better (i gotta thank everyone for their consolations, my family, friends, people of cf and a lot more, thank you everyone)
About the problems, i liked them, but they were too hard for me to solve, there were a lot of strong participants that managed to solve them, congrats (especially yutaka1999 for that impressive win, both on IMO and IOI)
I enjoyed this wonderful event, despite how i performed, hope everyone else enjoys it aswell

Our contestants told that the first time extension was around 15 seconds before the end of the 5 hours. Did you hear that announcement earlier?

Actually what is the reason of the second extension?

https://en.wikipedia.org/wiki/1972_Olympic_Men%27s_Basketball_Final

Pedrohso is an incredibly talented guy. I feel very proud by having taught him a few classes a while ago, and I'm happy he could overcome his past coding limitations and was able to fully showcase his problem solving skills. We Brazilians are all very excited about this result, which hopefully will get official soon! :D

???: Hi , so to me seems like a notorious coincidence.

Decent. Usually cutoffs are 1:2:3:6, there are more than 300 participants, and 150th has something like 135 as far as I remember

I believe it should be bronze. Half of the participants get medals and 144.99 seems to be in the first half.

P.S.

Though, it seems like the current standings are not the final standings for some odd reason.

Well, he is a tourist of last minute. He also raised score in last few seconds at some day of JOI Spring Camp :)

You don't have to wait for the judge to finish to resubmit. Also, in the last 15 minutes, submissions have no minimum interval. So submitting twice in the last minute is very normal...

I was lucky enough to sit next to him this year. He told me after the contest that he submitted in the last few seconds for Q5. He was very happy to find out 3 hours later during analysis time that he received 100 points :)

He said that in last minute he found some optimization and got 100. He didn't know that result until the analysis, since the scoreboard was broken.

Please send me my T-shirt for Bayan contest, lol

Lol. Care to elaborate what you mean, just a suggestion :)? There are a lot of ways you can think about this problem and there are a lot things you can simply don't care about if S=0. Don't expect us to know what you mean by "logic for S=0"

My first solution outputs 4 instead of 6 for this case.

3 1
2 1 0

5 2
4 3 2 1 0

10 5
8 3 6 1 4 5 2 7 0 9

9 3
1 0 4 3 2 8 7 6 5

:C

It was obvious, actually.

I did the same fucking thing and didn't get time to do ~30 points subtasks for silver. :(

Here is another example. I had Prize coded hour and a half in the contest, and it was correct with one tiny error: my bs was while l < r instead of l <= r, and I spent 3,5 next hours debugging it. I found my error literally minute until the end of the contest, fixed it, submitted, and then I realised I have commented a part of my code, for some kind of debugging. I deleted the comment, alt tabbed to the cms, but it was too late. In the analysis, that solution was accepted, without any changes. :(

It saves you the time and trouble of figuring out what subtask it is in your code. That's not what is being tested in IOI.

Also, this is the same rule as last year...

But, essentially, participants might produce multiple partial solutions, instead of one that solves all subtasks.

This has always been the case. For most problems and sets of subtasks, you can write a solution of the form

if input_looks_like_subtask_1():
  return brute_force()
elif input_looks_like_subtask_2():
  return solve_special_case()
else:
  solution_1 = apply_heuristic_that_doesnt_always_work()
  solution_2 = apply_another_heuristic()
  return whichever_looks_more_reasonable(solution_1, solution_2)

...and this is indeed what participants did, and indeed more or less what the jury expected them to do.

It's totally okay for participants to write partial solutions — indeed that is exactly what the entire concept of subtasks is for. Often it makes no sense to try to write a single solution that solves multiple subtasks: a reasonable IOI participant who cannot solve some problem completely might be able to solve subtask 1 with a bruteforce, and subtasks 2 and 3 might happen to be different special cases that can each be solved with a different special case solution. Requiring this participant to combine all three in a single file is just a waste of their time.

Thus the introduction of the "sum of scores of subtasks" rule doesn't really change anything about the spirit of the competition, but it does fix some awkward things that might happen without it, especially when feedback is broken (and I remember more recent IOIs where feedback was broken at some point than IOIs where it never was). Here's an anecdote that hits close to home: our own OVR in 2012 submitted a solution to some problem that solved subtasks A, B, C. Then feedback was broken (and never got fixed before the end of the contest), and OVR submitted another solution, which happened to solve A, B, D, but broke on C for some reason. Because of the broken feedback, he never learned about this until after the end of the context. (score(ABCD) — max(score(ABC), score(ABD))) would've been enough points to move him from bronze to silver, and the team wrote an appeal arguing that, if feedback was working as intended, he'd have noticed this and just submitted a "merged" solution that invokes his old one when ran on tests from subtask C. The appeal was almost granted, until someone from the jury noticed that the second submission was made less than a minute before the end of the competition, which meant it was quite unlikely he'd have managed to do the merging in time, so the appear was eventually denied. Had the new rule been in place back in 2012, Latvia would've had one more silver medal :)