#include<iostream>
#include<cmath>
#include<algorithm>
#define eps 1e-1
using namespace std;
struct point
{
	double x,y;
}ps[120];
point origin={0.0,0.0};

double cross(point a,point b,point c)
{
	return (a.x-c.x)*(b.y-c.y)-(a.y-c.y)*(b.x-c.x);
}

bool isinter(point a,point b,point c,point d)
{
	return fabs((a.x-b.x)*(c.y-d.y)-(a.y-b.y)*(c.x-d.x))!=0.0;
}

point inter(point a,point b,point c,point d)
{
	point res;
	double t1=cross(a,b,d),t2=cross(a,b,c);
	res.x=(t1*c.x-t2*d.x)/(t1-t2);
	res.y=(t1*c.y-t2*d.y)/(t1-t2);
	return res;
}
int n;
bool isconter()
{
	double res=0.0;
	ps[n]=ps[0];
	int i;
	for(i=0;i<n;++i)
		res+=cross(ps[i],ps[i+1],origin);
	return res>0;
}


int main()
{
	int cases;
	int i,j,k,s,t,r;
	point p;
	while(scanf("%d",&n),n)
	{
		for(i=0;i<n;++i)
			scanf("%lf%lf",&ps[i].x,&ps[i].y);
		if(!isconter())
			reverse(ps,ps+n);
		ps[n]=ps[0];
		for(i=0;i<n;++i)
		{
			for(j=i+1;j<n;++j)
			{
				if(isinter(ps[i],ps[i+1],ps[j],ps[j+1]))
				{
					p=inter(ps[i],ps[i+1],ps[j],ps[j+1]);
					for(k=0;k<n;++k)
					{
						if(cross(p,ps[k+1],ps[k])>eps)break;
					}
					if(k==n)
						break;
				}
			}
			if(j<n)break;
		}
		if(i>=n)
			printf("0");
		else
			printf("1");
		printf("\n");
	}
	return 0;
}

• Re:精度比较诡异,1e-1到1e-9都可以,0和1e-10就WA (552) Aloe 2008-09-12 22:42:30
  • Re:又一个XXXXX的 (568) GetAC 2008-09-12 22:47:14
    • Re:为什么会这样，，， (0) taishi 2010-03-30 20:55:50