Confused101's blog

Random point.
By Confused101, history, 8 years ago, In English

Given N rectangles which may or may not intersect. Report a random point Inside any rectangle. (probability of every point chosen must be equal). How to solve this problem?

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8 years ago, # |
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Points that appear in more that one rectangle have more probability or not?

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    8 years ago, # ^ |
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    No, every point should have same probability of being chosen irrespective of numbers of rectangles it appears in.

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      8 years ago, # ^ |
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      One more question :)...

      Could a rectangle have two or more of these N points in it?

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        8 years ago, # ^ |
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        There are N rectangles, you have to report random points inside any of these rectangles. Sorry if I was unclear, See image you need to report any random point from blue region. Image

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8 years ago, # |
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Partition the rectangle union into area-disjoint rectangles, choose a rectangle randomly accordingly to ratio of its area to sum of areas. Choose random (x,y) coordinate inside.

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    8 years ago, # ^ |
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    Looks good to me. Can you tell how can I "Partition the rectangle union into area-disjoint rectangles"? (algorithm)

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8 years ago, # |
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If coordinates are not big, you can get any random point until you get one which is inside one of the rectangles. That will still give you a uniform distribution although at a time complexity cost.

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