UVA 10005 Packing polygons(最小圆覆盖)

裸的模板题

AC代码：

 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 #include<iostream>
 #include<cstring>
 using namespace std;
 typedef long long ll;
 const double eps = 1e-;
 const double pi = acos(-1.0);
 const int maxp = ;
 int sgn(double x)
 {
     if(fabs(x) < eps) return ;
     else return x <  ? - : ;
 }
 struct Point{
     double x, y;
     Point(){}
     Point(double _x, double _y){
         x = _x, y = _y;
     }
     void input(){
         scanf("%lf%lf", &x, &y);
     }
     bool operator == (Point b) const{
         return sgn(x - b.x) ==  && sgn(y - b.y) == ;
     }
     bool operator < (Point b)const{
         return sgn(x - b.x) ==  ? sgn(y - b.y < ) : x < b.x;
     }
     Point operator - (const Point &b)const{
         return Point(x - b.x, y - b.y);
     }
     //²æ»ý
     double operator ^(const Point &b){
         return x * b.y - y * b.x;
     }
     //µã»ý
     double operator *(const Point &b){
         return x * b.x + y * b.y;
     }
     double len(){
         return hypot(x, y);
     }
     double len2(){
     return x * x + y * y;
     }
     double distant(Point p){
         return hypot(x - p.x, y - p.y);
     }
     Point operator + (const Point &b)const{
         return Point (x + b.x, y + b.y);
     }
     Point operator * (const double &k)const{
         return Point(x * k, y * k);
     }
     Point operator / (const double &k)const{
         return Point(x / k, y / k);
     }
     Point rotate(Point p, double angle){
         Point v = (*this) - p;
         double c = cos(angle), s = sin(angle);
         return Point(p.x + v.x * c - v.y * s, p.y + v.x * s + v.y * c);
     }
 };
 struct polygon{
     int n;
     Point p[maxp];
     void add(Point q){
         p[n ++] = q;
     }
     void input(int _n){
         n = _n;
         for(int i = ;i < n;i++) p[i].input();
     }
     Point circumcenter(const Point &a,const Point &b,const Point &c) {
         //返回三角形的外心
         Point ret;
         double a1 = b.x - a.x, b1 = b.y - a.y, c1 = (a1*a1+b1*b1) / ;
         double a2 = c.x - a.x, b2 = c.y - a.y, c2 = (a2*a2 + b2*b2) / ;
         double d = a1 * b2 - a2 * b1;
         ret.x = a.x + (c1*b2 - c2*b1) / d;
         ret.y = a.y + (a1*c2 - a2*c1) / d;
         return ret;
     }
     void min_cover_circle(Point &c,double &r) { // p为点的集合；c为圆心，r为半径
         random_shuffle(p,p+n);
         c = p[];
         r = ;
         for(int i = ; i < n; i++) {
             if(c.distant(p[i]) > r + eps) {
                 c = p[i];
                 r = ;
                 for(int j = ; j < i; j++){
                     if(c.distant(p[j]) > r + eps) {
                         c.x = (p[i].x + p[j].x) / ;
                         c.y = (p[i].y + p[j].y) / ;
                         r = c.distant(p[j]);
                         for(int k = ; k < j; k++) {
                             if(c.distant(p[k]) > r + eps) {
                             c = circumcenter(p[i],p[j],p[k]);
                             r = c.distant(p[i]);
                             }
                         }
                     }
                 }
             }
         }
     }
 };
 int main()
 {
     int n;
     double r;
     double ans;
     while(~scanf("%d",&n) &&n)
     {
         polygon a;
         Point c;
         a.input(n);
         scanf("%lf",&r);
         a.min_cover_circle(c,ans);
         if(ans <= r) printf("The polygon can be packed in the circle.\n");
         else printf("There is no way of packing that polygon.\n");
     }
     return ;
 }