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MarioYC's blog

SPOJ UNTITLED
By MarioYC, 14 years ago, In English

Could anyone give me a hint on how to solve this problem?

I solved POJ 3167 in which the problem was based using a modified KMP, but i couldn't come up with anything that solves UNTITLED.

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14 years ago, hide # |
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I can`t understend why answer is "1 2 3".

1 because {1}={2}, 2 because {3,1}={10,1}, and what is 3?

UPD. understood

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14 years ago, hide # |
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Maybe in KMP:

a[0]...a[i]...a[j]...a[k]

a[0]...a[i]==a[j]...a[k] if a[0]...a[i-1]==a[j]...a[k-1] and a[i]==a[k].

a[i]==a[k] if and only if count of numbers which greather then a[i] in a[0]..a[i-1] is equal to count of numbers which greather then a[k] in a[j]..a[k-1].

We can use the struct like segment tree, which help us get this count in O(log(400000)) (just +1 to a[i] when we add number a[i] ans -1 else). If we get suffix(a[j]..a[k-1]) we don't forget to decrease all values which don't include to this suffix (it's a[j]..a[h], if a[j]..a[k-1]=a[j]..a[h]a[h+1]..a[k-1]). And first we should decrease all numbers as it possibly in any sequence because numbers are in the range 1..2^32 (then we can use a segment tree).

I don't know is it correct solution, but maybe.

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    14 years ago, hide # ^ |
     
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    Yes, I did something like that for POJ 3167, using a BIT. But in that problem we only need to match one pattern. In SPOJ UNTITLED you need to match many patterns.

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read the solution to ceoi 2011 Matching

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