最小圆覆盖

struct Point{double x,y;};     
struct Circle{Point c;double r;};     
double dist(Point a,Point b){   
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));     
}     
Circle calc(Point p1,Point p2,Point p3){     
    Circle temp;     
    double a,b,c,d,e,f;     
    a=p2.x-p1.x;     
    b=p2.y-p1.y;     
    c=(p2.x*p2.x+p2.y*p2.y-p1.x*p1.x-p1.y*p1.y)/2;     
    d=p3.x-p1.x;     
    e=p3.y-p1.y;     
    f=(p3.x*p3.x+p3.y*p3.y-p1.x*p1.x-p1.y*p1.y)/2;     
    temp.c.y=(c*d-f*a)/(b*d-e*a);     
    temp.c.x=(c*e-f*b)/(a*e-b*d);     
    return temp;     
}     
Circle minC(Point *p,int n){     
    Circle O;     
    int i,j,k;     
    O.c=p[0];O.r=0;  
    for(i=1;i<n;i++){    
        if(dist(O.c,p[i])<=O.r+1e-6)continue;     
        O.c=p[i];O.r=0;     
        for(j=0;j<i;j++){     
            if(dist(O.c,p[j])<=O.r+1e-6)continue;     
            O.c.x=(p[i].x+p[j].x)/2;O.c.y=(p[i].y+p[j].y)/2;O.r=dist(O.c,p[j]);     
            for(k=0;k<j;k++){    
                if(dist(O.c,p[k])<=O.r+1e-6)continue;     
                O=calc(p[i],p[j],p[k]);     
                O.r=dist(O.c,p[k]);     
            }     
        }     
    }     
    return O;     
}