2
2
5 10 5 8 3 10 3 8
8 8 8 6 7 8 7 6
1
0 0 2 2 2 0 0 2

Case #1:
17
Case #2:
4

ac代码

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
using namespace std;
#define PR 1e-8
#define N 4010
#define maxdouble 1e20
struct TPoint
{
    double x,y;
};
struct TPolygon
{
    int n;
    TPoint p[N];
}ply;
double MIN(double a,double b) {return a>b?b:a;}
int dblcmp(double a)
{
    if(fabs(a)<PR) return 0;
    return a>0?1:-1;
}
double dist(TPoint a,TPoint b)
{
    double s1=a.x-b.x;
    double t1=a.y-b.y;
    return sqrt(s1*s1+t1*t1);
}
double cross(TPoint a,TPoint b,TPoint c)
{
    double s1=b.x-a.x;
    double t1=b.y-a.y;
    double s2=c.x-a.x;
    double t2=c.y-a.y;
    return s1*t2-s2*t1;
}
double dot(TPoint a,TPoint b,TPoint c)
{
    double s1=b.x-a.x;
    double t1=b.y-a.y;
    double s2=c.x-a.x;
    double t2=c.y-a.y;
    return s1*s2+t1*t2;
}
bool cmop(TPoint a,TPoint b)
{
    if(fabs(a.x-b.x)<PR) return a.y<b.y;
    else return a.x<b.x;
}
bool cmp(TPoint a,TPoint b)
{
    int d1=dblcmp(cross(ply.p[0],a,b));
    return d1>0||(d1==0&&dist(ply.p[0],a)<dist(ply.p[0],b));
}
TPolygon graham()
{
    int i,top=2;
    for(i=2;i<ply.n;i++)
    {
        while(top>1&&(dblcmp(cross(ply.p[top-2],ply.p[i],ply.p[top-1])))>=0) top--;
        ply.p[top++]=ply.p[i];
    }
    ply.n=top;
    return ply;
}
double solve()
{
    int i,p=1,q=1,r;
    double minarea=maxdouble,area;
    ply.p[ply.n]=ply.p[0];
    for(i=0;i<ply.n;i++)
    {
        while(dblcmp(cross(ply.p[i],ply.p[i+1],ply.p[p+1])-cross(ply.p[i],ply.p[i+1],ply.p[p]))>0)
            p=(p+1)%ply.n;
        while(dblcmp(dot(ply.p[i],ply.p[i+1],ply.p[q+1])-dot(ply.p[i],ply.p[i+1],ply.p[q]))>0)
            q=(q+1)%ply.n;
        if(i==0) r=q;
        while(dblcmp(dot(ply.p[i],ply.p[i+1],ply.p[r+1])-dot(ply.p[i],ply.p[i+1],ply.p[r]))<=0)
            r=(r+1)%ply.n;
        double d=dist(ply.p[i],ply.p[i+1])*dist(ply.p[i],ply.p[i+1]);
        area=cross(ply.p[i],ply.p[i+1],ply.p[p])*(dot(ply.p[i],ply.p[i+1],ply.p[q])-dot(ply.p[i],ply.p[i+1],ply.p[r]))/d;
        minarea=MIN(area,minarea);
    }
    return minarea;
}
int main()
{
	int t,cot=0;
	scanf("%d",&t);
    while(t--)
    {
        int i,n;
        double area;
		scanf("%d",&n);
		ply.n=n*4;
        for(i=0;i<ply.n;i++) scanf("%lf%lf",&ply.p[i].x,&ply.p[i].y);
        sort(ply.p,ply.p+ply.n,cmop);
        sort(ply.p+1,ply.p+ply.n,cmp);
        ply=graham();
        if(ply.n<3) area=0;
        else area=solve();
		printf("Case #%d:\n",++cot);
        printf("%.lf\n",area);
    }
    return 0;
}