A Simple and Fast Algorithm for Detecting the Convexity and Concavity of Vertices for an Arbitrary Polygon
任意多边形顶点凸、凹性判别的简捷算法

A simple and fast algorithm for detecting the convexity and concavity of vertices for an arbitrary polygon is presented, which needs 2n+4 multiplications, 5n+10 additions or subtractions and 2n+3 comparisons (n is the number of the vertices of the polygon). Meanwhile, the sufficient and necessary condition for the orientation of an arbitrary simple polygon is given.