[HNOI2019] fish

[HNOI2019] fish

Portal

Luogu
sons

Solution

Enumeration \ (A \) point and \ (D \) points, found \ (B, C \) point \ (E, F \) there is no restriction between points, then consider seeking separate \ (B, C \) of and \ (E, F \) pairs.

Part.1

Seeking \ (B, C \) points to the number.
Obviously \ (the AD \) is \ (the BC \) in the perpendicular, consider enumeration \ (B, C \) points, for which the vertical line survive.
enum \ (a, D \) may be used when \ (upper \ _bound \) is determined in the range of.

Part.2

Seeking \ (E, F \) number of points.
Consideration enumeration \ (D \) point, the polar angle other sorting points, it can be used for each of the double pointer \ (A \) point determined feasible \ ( E \) , \ (F. \) number of points.
may be \ (Map \) are kept down to the corresponding distances.

Code

u1s1, this question I \ (eps \) to open \ (1e-7 \) to \ (Wa \) , open \ (1e-10 \) to \ (AC \) KHX.
Code