计算几何(二维) 基本组件(1)

1.判断点是否在直线上: . 1.差积为零 2.点击小于零 bool OnSegment(Point P,Point A,Point B) { return dcmp(Cross(A-P,B-P))==0 && dcmp(Dot(A-P,B-P))<=0; } 2.点到直线的距离: double DistanceToLine(Point P,Point A,Point B) { Vector v1=B-A,v2=P-A; return fabs(Cross(v1,v2))/Length(v1); } 3.点到线段的距离: 分四种情况: