包含一些点与直线，线段的操作

凸包的构建与判断之类的操作

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          using namespace std;const double eps=1e-6;const double Pi=acos(-1.00);inline int dcmp(double x){ if(x>eps)return 1; return x<-eps?-1:0;}struct Vector{ double x,y; Vector(double X=0,double Y=0) { x=X,y=Y; } bool operator < (const Vector &b)const { return dcmp(x-b.x)==0?y
          
           
            0;}void sort_point(Point *s,int L,int R,Point base){ Base=base; sort(s+L,s+1+R,cmp_ang); return;}struct Polygon{ Point node[10025]; Line edge[10025]; int cnt; double C; double A; void build_edge() { for(int i=1;i
            
             0)ans++; } else if(on_seg(s2,ray)) { if(dcmp(s2.y-s1.y)>0)ans++; } else if(is_cross(ray,edge[i]))ans++; } if(ans%2==1)return 1; return -1; } bool circle_is_in_polygon(Circle a) { if(is_in_polygon(a.O)<0)return false; for(int i=1;i<=cnt;i++) if(dcmp(dist(a.O,get_nearest_point_on_segment(a.O,edge[i]))+eps-a.R)<0)return false; return true; } void get_convex_hull(Point *s,int num) { if(num==0) { cnt=0; return; } if(num==1) { cnt=1; node[1]=s[1]; return; } if(num==2) { cnt=2; node[2]=s[2]; node[1]=s[1]; return ; } for(int i=1;i<=num;i++) if(s[i]
             
              =2&&dcmp(cross(node[cnt]-node[cnt-1],s[i]-node[cnt-1]))<=0)cnt--; node[++cnt]=s[i]; } return; } double get_Circumference() { C=0; for(int i=1;i<=cnt;i++) C+=dist(edge[i].s,edge[i].e); return C; } double get_Area() { A=0; for(int i=1;i