# Concave polygons overlapping test

I have set of $N$ concave polygons, given as list of 2D Euclidean coordinates. How to compute:

a. if any of them are overlapping?

b. if one arbitrarily selected polygon overlaps with any of the remaining $N-1$ polygons?

No need for obtaining points of intersection of the polygon's borders. The second answer b is sufficient, but maybe there also exists specialized algorithm for answering a.

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Do you consider two polygons that share an edge to be overlapping? –  apnorton Dec 9 '12 at 14:12
And, are these integer coordinates or floats? (I'm asking this because it sounds like a programming problem...) –  apnorton Dec 9 '12 at 14:19
For b, could you use the algorithm described here? stackoverflow.com/questions/2272179/… –  apnorton Dec 9 '12 at 14:51
@anorton: floats. Sharing edge could mean no-overlapping –  Sydnic Dec 9 '12 at 15:26