UVA 10652 Board Wrapping(二维凸包)

#include <math.h>
#include <stdio.h>
#include <algorithm>
using namespace std;
typedef struct Point{
    double x,y;
    Point(double x=0,double y=0):x(x),y(y){}
}Vector;
Vector operator + (Vector A,Vector 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);
}
bool operator <(const Point &a,const Point &b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
double Cross(Vector A,Vector B)
{
    return A.x*B.y-A.y*B.x;
}
Vector Rotate(Vector A,double rad)
{
    return Vector(A.x*cos(rad)-A.y*sin(rad),A.x*sin(rad)+A.y*cos(rad));
}
double ConvexPolygonArea(Point *p,int n)
{
    double area=0;
    for(int i=1;i<n-1;i++)
        area+=Cross(p[i]-p[0],p[i+1]-p[0]);
    return area/2;
}
double torad(double deg)
{
    return deg/180*acos(-1);
}
int ConvexHull(Point *p,int n,Point* ch) //注意是*ch
{
    sort(p,p+n);
    int m=0;
    for(int i=0;i<n;i++)
    {
        while(m>1&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0) m--;
        ch[m++]=p[i];
    }
    int k=m;
    for(int i=n-2;i>=0;i--)  //注意是--不是++
    {
        while(m>k&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0) m--;
        ch[m++]=p[i];
    }
    if(n>1) m--;
    return m;//别忘了加m
}
int main()
{
    int T;
    Point P[2500],ch[2500];
    scanf("%d",&T);
    while(T--)
    {
        int n,pc=0;
        double area1=0;
        scanf("%d",&n);
        for(int i=0;i<n;i++)
        {
            double x,y,w,h,j,ang;
            scanf("%lf%lf%lf%lf%lf",&x,&y,&w,&h,&j);
            Point o(x,y);
            ang=-torad(j);
            P[pc++]=o+Rotate(Vector(-w/2,-h/2),ang);
            P[pc++]=o+Rotate(Vector(w/2,-h/2),ang);
            P[pc++]=o+Rotate(Vector(-w/2,h/2),ang);
            P[pc++]=o+Rotate(Vector(w/2,h/2),ang);
            area1+=w*h; //矩形总面积
        }
        int m=ConvexHull(P,pc,ch);
        double area2=ConvexPolygonArea(ch,m); //凸包面积
        printf("%.1lf %%\n",area1*100/area2);
    }
    return 0;
}