convhull

Description: Let n points in the plane as the coordinate origin is. The following methods can be obtained by including the n-point convex polygon. (1) Find the right of the point, the x coordinate of the maximum point, is set. (2) as the center point, the remaining points in the selection and counterclockwise rotation in the smallest point set. (3) then as the center point, the remaining points in the selection and counter-clockwise rotation of the smallest point. And so on, until the new selected points coincide with the point up. Let k points have been obtained in order for the polygon, where the first point coincides with point 1. Point of the triangle is the vertex of each area and the sum can be calculated.