uva 10652 Board Wrapping

主要是凸包的应用；

 #include <cstdio>
 #include <cmath>
 #include <cstring>
 #include <algorithm>
 #include <vector>
 #define eps 1e-9
 using namespace std;
 const double pi = acos(-);

 int dcmp(double x)
 {
     return fabs(x) < eps ?  : (x >  ?  : -);
 }

 struct Point
 {
     double x;
     double y;

     Point(double x = , double y = ):x(x), y(y) {}

     bool operator < (const Point& e) const
     {
         return dcmp(x - e.x) <  || (dcmp(x - e.x) ==  && dcmp(y - e.y) < );
     }

     bool operator == (const Point& e) const
     {
         return dcmp(x - e.x) ==  && dcmp(y - e.y) == ;
     }
 };

 typedef Point Vector;

 Vector operator + (Point A, Point B)
 {
     return Vector(A.x + B.x, A.y + B.y);
 }

 Vector operator - (Point A, Point B)
 {
     return Vector(A.x - B.x, A.y - B.y);
 }

 Vector operator * (Point A, double p)
 {
     return Vector(A.x * p, A.y * p);
 }

 Vector operator / (Point A, double p)
 {
     return Vector(A.x / p, A.y / p);
 }

 double cross(Point a,Point b){return a.x*b.y-a.y*b.x;}
 Point rotate(Point a,double ang){return Point(a.x*cos(ang)-a.y*sin(ang),a.x*sin(ang)+a.y*cos(ang));}
 int convexhull(Point *p,int n,Point *ch)
 {
     sort(p,p+n);
     int m=;
     for(int i=;i<n;i++)
     {
         while(m>&&cross(ch[m-]-ch[m-],p[i]-ch[m-])<=)m--;
         ch[m++]=p[i];
     }
     int k=m;
     for(int i=n-;i>=;i--)
     {
         while(m>k&&cross(ch[m-]-ch[m-],p[i]-ch[m-])<=)m--;
         ch[m++]=p[i];
     }
     if(n>)m--;
     return m;
 }
 Point p[],ch[];
 int main()
 {
     int t,n;
     double alph,x,y,h,w,area1,area2;
     scanf("%d",&t);
     while(t--)
     {
         area1=area2=;
         scanf("%d",&n);
         int pc=;
         for(int i=;i<n;i++)
         {
             scanf("%lf%lf%lf%lf%lf",&x,&y,&w,&h,&alph);
             Point o(x,y);
             double ang=-(alph*pi/);
             p[pc++]=o+rotate(Point(-w/,-h/),ang);
             p[pc++]=o+rotate(Point(w/,-h/),ang);
             p[pc++]=o+rotate(Point(-w/,h/),ang);
             p[pc++]=o+rotate(Point(w/,h/),ang);
             area1+=w*h;
         }
         int m=convexhull(p,pc,ch);
         for(int i=;i<m;i++)
             area2+=cross(ch[i]-ch[],ch[i+]-ch[]);
         area2/=;
         printf("%.1lf ",area1/area2*);
         puts("%");
     }
     return ;
 }