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(-1);

int dcmp(double x)
{
    return fabs(x) < eps ? 0 : (x > 0 ? 1 : -1);
}

struct Point
{
    double x;
    double y;

    Point(double x = 0, double y = 0):x(x), y(y) {}

    bool operator < (const Point& e) const
    {
        return dcmp(x - e.x) < 0 || (dcmp(x - e.x) == 0 && dcmp(y - e.y) < 0);
    }

    bool operator == (const Point& e) const
    {
        return dcmp(x - e.x) == 0 && dcmp(y - e.y) == 0;
    }
};

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=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--)
    {
        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;
}
Point p[2500],ch[2500];
int main()
{
    int t,n;
    double alph,x,y,h,w,area1,area2;
    scanf("%d",&t);
    while(t--)
    {
        area1=area2=0;
        scanf("%d",&n);
        int pc=0;
        for(int i=0;i<n;i++)
        {
            scanf("%lf%lf%lf%lf%lf",&x,&y,&w,&h,&alph);
            Point o(x,y);
            double ang=-(alph*pi/180);
            p[pc++]=o+rotate(Point(-w/2,-h/2),ang);
            p[pc++]=o+rotate(Point(w/2,-h/2),ang);
            p[pc++]=o+rotate(Point(-w/2,h/2),ang);
            p[pc++]=o+rotate(Point(w/2,h/2),ang);
            area1+=w*h;
        }
        int m=convexhull(p,pc,ch);
        for(int i=1;i<m;i++)
            area2+=cross(ch[i]-ch[0],ch[i+1]-ch[0]);
        area2/=2;
        printf("%.1lf ",area1/area2*100);
        puts("%");
    }
    return 0;
}