You had WA24 As I now!
What changing in your program had effect?

Yes!
I gone throught test 24.
The problem was how use eps=0.00000000001!?
Before I used it in many places of program.
After I am use eps only in one moment: I make
rectangles wider by eps. In other places I accept eps=0.

But finally in verification S>=0.5+20*eps
I used 20*eps as possible error for wrong 20
intersections after eps- widering.

Edited by author 27.01.2009 19:29

Find it as intersection of two arbitrary convex polygons, otherwise you'll bury yourself in special cases.

To do so get all points of one polygon inside the other, all points of the other polygon inside the first one, and also all their intersections by non-parallel sides.

Then find area of their convex hull. Angle/distance sorting step is enough to find that hull.

What do you mean by "symmetric"? It's 45-degrees turn.

just do what they ask you. Rotate the field and find intersection of new sqare with old squares.