ABC016D

https://gyazo.com/ef23ddd076030dd0b8a2ceedbd0ff39d

Thoughts.

This is a pain in the ass.

Determine the intersection of line segments and sort the intersection points

Alternate because we know the chop starts from the outside.

Connect odd-numbered intersections with even-numbered intersections. Since we are dealing only graphically, it is sufficient to connect the two ends of the cut edges, but it is necessary to avoid twisting the edges.

We can't use the inner product to determine that, so we'll do a line segment crossing determination.

Once you have the edge set, just count the number of connected components.

I see, just project it onto the normal vector and see if the signs are reversed.

I've got an article up to the point where I'm looking for intersections, so I'll put it in my library later.

Official Explanation

Oh, I only counted the number of cut edges.

Okay, you say "polygonal" so there are no holes.

I thought too hard.

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