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nownikhil's blog

Interesting Line Sweep Problem
By nownikhil, 10 years ago, In English

Hi all,

I was trying to solve this problem on spoj. http://www.spoj.com/problems/WILD/

If we treat each evil candidate as a point and consider the cube (0,0,0) — (x,y,z). The problem is reduced to finding the volume of union of cubes. The answer in this case will be m^3 — volume.

The complexity is turning out to be n*n*log(n). Can anyone suggest a better algorithm?

Thanks

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10 years ago, # |
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You can do it in O(n * log2(n)) in the same way you find the area of the union of rectangles in O(n * log(n)), by using segment trees, and in each leaf, another segment tree...

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    10 years ago, # ^ |
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    Can you explain a little more about the implementation? Or if you can post a pseudo code for the same.

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