Azret's blog

IZhO 2015 Problems
By Azret, history, 10 years ago, translation, In English

Hello.

UPD Old links don't work. New: https://www.dropbox.com/sh/b9apawmc61mzq3p/AADvGv3iF6cHwEEJ4anth5IYa?dl=0

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9 years ago, # |
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Where I can submit my solutions?

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    9 years ago, # ^ |
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    IDK really. I tried to find out but couldn't find anything.

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    9 years ago, # ^ |
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    you can submit problems in exam :)HAHA

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9 years ago, # |
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Can anyone who solved problem A explain their solution?

I was thinking of a hacky solution of creating segtree storing xor, sum, product(mod prime) of a range in node, then query to check if those properties are equal. I do not ex[pect this to be the official solution. Can anyone post the solution/hints?

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    9 years ago, # ^ |
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    Hint: For each number remember nearest left/right element with same value. It's easy to change this value during update.

    If a[l,r] is a permutation: 1) Minimum is 1

    2) Maximum is r-l+1

    3) All elements are distinct( minimum of left values <= l)

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    9 years ago, # ^ |
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    Create a segment tree and store sum of where . To check just compare the sum of segment with . Update is easy.

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