sevenkplus's blog

By sevenkplus, 8 years ago, In English,

Team member: chnlich scottai1 zpl2 sevenkplus

WJMZBMR failed on one physics problem on day 1. s-quark failed on one string problem on day 2. (He implemented suffix automaton, with a little issue. )

 
 
 
 
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8 years ago, # |
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Any problemset\standings available ?

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    8 years ago, # ^ |
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    I haven't seen any online version yet.

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    8 years ago, # ^ |
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    Problemset-Day1 Problemset-Day2 (The statements are in Chinese. Maybe someone would translate it. )

    Testdata

    It seems that there are some problems in the testdata of "rev" and "extreme".

    (I'm not sure if this website can be visited outside China. May anyone tell me? )

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      8 years ago, # ^ |
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      Perhaps you can add it to Codeforces::Gym?

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        8 years ago, # ^ |
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        In Endlish, please :)

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8 years ago, # |
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Yep. Maybe it's time to create topic with IOI participants and their nicks on CF and TC?

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    8 years ago, # ^ |
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    Has Russian IOI team been already selected?

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      8 years ago, # ^ |
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      As far as I know, there will be summer training camp, where our national IOI team will be selected.

      Of course, there are not many candidates now :)

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      8 years ago, # ^ |
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      It'll be finally selected at the beginning of July.

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There were only two contests?

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    8 years ago, # ^ |
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    There are also some tests focusing on the contestant's overall quality.

    And, there are several rounds.

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      8 years ago, # ^ |
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      Could you tell about these tests? What is it like? Contests, yes/no tests or something else?

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8 years ago, # |
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What is Physics problem? IOI's olympiad in informatics, isn't it?

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    8 years ago, # ^ |
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    May be he means something like problem G (VKOSHP), where you need to know some physics basics to solve it?

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      8 years ago, # ^ |
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      If so, it looks strange, because such problems usually doesn't require any skills except very basic school physics.

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        8 years ago, # ^ |
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        It may be simple unluck, or may be this problem required some tricky algorithms except physics?

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        8 years ago, # ^ |
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        Who cares about physics preparing for IOI selection?:)

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        8 years ago, # ^ |
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        Indeed, it needs only basic school physics. But it seems that some contestants aren't familiar with it.

        The problem is: Given a tree-like resistive network in which all leafs are connected to ground. Every single wire is 1 Ohm.

        Modification: Add a power supply in one direction on one node. Query: The potential of one node to ground.

        N <= 5*10^4 longest chain of the tree <= 50 (to avoid some annoying precision issues)

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    8 years ago, # ^ |
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    Sigh...The problem is look like that: Given you a tree-like electric network and put some source on it,and link the leaf nodes with the ground and assume the ground's potential is 0.

    the tree's max-length path is 50.

    And you're required to support two operations:

    1.put a source on a edge of tree. 2.query one node's potential.

    ...I'm no familiar with that kind of problems, some competitors get the the full score and I only get 20 points...

    Sigh...I think it's not fair to put that kind of problem with complex physical background in a OI-based contest....

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      8 years ago, # ^ |
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      It's a bit strange that you know Kirchoff's law but do not know the voltage divider rule.

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        8 years ago, # ^ |
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        I didn't figure out that each source are independent...I know the voltage divider rule that time...

        It's only a excuse for me...I would study physic harder next year...

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      8 years ago, # ^ |
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      Yeah, it's a pity that IOI selection was decided on that :(

      But how come it's just one problem that decides who gets on the team and who doesn't? How many problems in total affect the selection?

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        8 years ago, # ^ |
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        There two days in Chinese Team Selection Contest..

        And the score is calculated by the formula : your score/ max score *35.

        The first problem in day 1 is very hard and the third problem is relatively easy,so the result on day 1 is some how based on that physical problem T_T.The top 6 in the final standing all get 60 or more points on that physical problem.

        And the day2's problem are very easy...Many competitors get good result,although xujie get the 1st place in day 2 and I get the 2nd place in day 2...me ended 7th end 8th finally...

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          8 years ago, # ^ |
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          Yeah, now I understand — it looks like the selection system is quite prone to this kind of thing happening.

          When I was a participant at the Russian IOI camps, there was about 12 days on average that decided the team, not 2, so it was much more stable and most gaps were more than one problem.

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            8 years ago, # ^ |
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            In fact, we have 12 trials which each of the contestants write a problemset, and others tries to solve it. It is only worth 10 score. WJMZBMR got full score in this part!!!

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            8 years ago, # ^ |
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            And there is also an assignment which is worth 5 score. WJMZBMR also got full score...

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        8 years ago, # ^ |
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        Your final score in each day = you score / maximum score * 35. In day 1, the other 2 problems are not easy to get high score. So, knowing physics leads you to top 6. And the gap between contestants who can do the physics problem and those who can not is very large.

        TAT ...Why I have got negative votes...

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      8 years ago, # ^ |
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      wo cao, ni men dou hui shuo english!!

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Rough selection... :/

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Congratulate for those who entered the national teams.... Maybe I can make it next years...Sigh...

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    8 years ago, # ^ |
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    Don't be upset and be a true man, you certainly can make it.

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    ...It is a pity that you have no chance to defeat tourist in IOI...

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    How old are you and how many years left you have at high school? To be honest, I was thinking you're much older (at least, college student) judging by your high rating. Some time ago I've decided to read the code of the best contestants (top 10) after the contest to improve my performance and I've found your code is the most clear and understandable (along with rng_58 who is my 2nd favorite contestant) so it's even more surprising for me to know you're still at high school. Anyway, I wish you good luck next year — tourist is retired this year so you have chance to place top instead of him ^_^

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      8 years ago, # ^ |
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      According to this, tourist was born in 1994 so, for the age limit, he can attend also IOI 2013

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        He finishes school this year.

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          In that case, I join with you and wish good luck to WJMZBMR for next IOI :)

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        For the age limit, Gennady can attend also IOI 2013, 2014.

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          I don't think he's going to deliberately fail school only to attend more IOIs. Besides, the ICPC is waiting. ;)

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Admire China team members!!! Wish their great success in IOI!!!

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    How many years old that a Chinese student can become an IOIer? In some country, it's only 17 and 18 :)

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      As long as you are in high school, and haven't yet got gold medal in previous IOI.

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Hi,

I think for Day 2 Q2, some formulae are missing. Could you please give us the complete problem statement for Q2? Thank you very much!

What I have gotten from the problem statement is that, you are given a set of points. Then all values within the convex hull of the set of points (including on the boundary) has value 1, while every other point has value 0. Then, you are given 2 sets of points, and you want to satisfy something.

May I know the full problem statement? Thank you very much!

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    8 years ago, # ^ |
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    I'm sorry. Some formulae are missing.

    As I haven't seen other online versions, I took two photos of the problem statement.

    extreme.part1 extreme.part2

    I hope the photos are clear enough.

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      8 years ago, # ^ |
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      Thank you!

      Wondering, for the string problem on day 2, other than suffix automaton, are there other methods of solving the problem?

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        8 years ago, # ^ |
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        Suffix array, with lots of constant optimization.

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7 years ago, # |
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ORZ FHQ!