hogloid's blog

Announcement of JOI Open Contest 2013
By hogloid, 11 years ago, In English

Subsequently to the JOI Ninja Contest last year(http://codeforces.me/blog/entry/5262 ), JOI (Japanese Olympiad in Informatics) will hold a contest mainly for high-school students who enter IOI this year(of course, everyone can participate)

the site is here : http://cms.ioi-jp.org/

I hope it will help you prepare for IOI :)

UPD: The ranking system is not a perfect one,it is refreshed with delay now. In the actual contest, it will be refreshed once in 5 or 10 minutes,but some trouble may occur,so please don't trust the ranking absolutely.

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11 years ago, # |
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This contest in last year is here.

http://joiopen2012.contest.atcoder.jp/

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11 years ago, # |
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I have a problem, i used my Facebook account for login and i submitted a solution but i can't see my name in standing. [sry for poor English]

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    11 years ago, # ^ |
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    thanks , I tried and had the same problem.

    I ask the developer to fix the problem.

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    11 years ago, # ^ |
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    Sorry, the ranking system is not perfect now. We think that names not shown in the rankings is not due to Facebook login. maybe it will be fixed , so please wait a while...

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11 years ago, # |
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I don't think that authentication with Facebook/Twitter is a feature available in CMS by default. If so, are your patches implementing this feature available somewhere?

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11 years ago, # |
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When logging in with Facebook account I have to share (with JOI) my friends list. I don't want to do that. It seems to be a strange requirement before joining the contest.

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    11 years ago, # ^ |
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    If you don't want to let us know the information,please make a dummy account of twitter or Facebook.(I think twitter is easier) Then you can join the contest without any information.

    The development seems so busy that the system is not a complete one. Sorry for inconvenience.

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    11 years ago, # ^ |
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    I don't think it's possible not to request access to the user's friend list, that's just the way Facebook API works.

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11 years ago, # |
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And what if there exist a National Firewall against Facebook and Twitter ? Can't I participate ? Or should I do some illegal(?) stuff like proxies ? :(

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    11 years ago, # ^ |
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    I'm afraid that the answer is No,you can't. There's no registration form so far.

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11 years ago, # |
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It starts soon~~

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11 years ago, # |
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can we see others solution and test data after contest finished.

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    11 years ago, # ^ |
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    I think CMS doesn't show the contestants' codes,like you can't see codes of IOI.

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      11 years ago, # ^ |
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      but last year we can see others solutions.

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        11 years ago, # ^ |
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        Really? I didn't know that;I ask the developer. But I think it can't ,because we didn't promised that the codes will be shown.

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          11 years ago, # ^ |
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          in problem B i cant get 30 points from subtask 2 and i cant understand why ? my solution is this Could you look my solution what is wrong ?

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            11 years ago, # ^ |
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            well,I can't debug your code;I don't like debugging.

            For me,it doesn't need segment tree ;like this

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        11 years ago, # ^ |
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        The contest system of last year's contest was Atcoder, but this year it is CMS. That is why you can't see others' code this year, I think.

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11 years ago, # |
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Interesting contest! The first subtask for problem B was even more difficult for me than the second one. I wonder how to solve A&B efficiently?

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    11 years ago, # ^ |
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    Subtask 1 of B: First,get the last condition how edges are connected. Next,reverse all events,and mark the nodes which are connected to C1 at the last moment. Then,Process events — just ignore erasing event and when an edge is connected and one side of it is marked,mark the other node ,and nodes from there on. (this works because all marked nodes are connected area)

    Problem A

    I took a way as follows: first,there are n groups consists of 1...n state each. Unite small two groups adjacent to each other,and make the number of groups be K. Then,delete a providence from largest district,that is adjacent to other district.Note that the deleted providence must not be a articulation node of the district. Just repeat this many times,and I got 90.(of course, I take specialized way for subtask 1&2)

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11 years ago, # |
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How to solve C for 100 points? Am i right that for 50 points we just use binary search + dynamic?

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    11 years ago, # ^ |
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    i think your dp is f(position,how many p , how many q) = 1 or 0

    u must use this for O(N^2) ~~~~~ f(position,p) = minimum q ~~~~~ with dynamic

    algorithm is O(N^2) * log(N)

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