convhull

说明：  设平面上n个点为 ，坐标原点为 。可按照下面方法求得包含这n个点的凸多边形。 (1)求最右边点，即x坐标最大点，设为 。 (2) 以 点为中心，在其余 个点中选取与 逆时针旋转角度最小的点，设为 。 (3)再以 点为中心，在其余 个点中选取与 逆时针旋转角度最小的点 。如此类推，直到新选取的点与 点重合为止。设已求得多边形k个点依次为 ，其中第 点与第1点重合。则分别以点 为三角形顶点计算面积并求和即可。
(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.)