poj 3304

#include<stdio.h>

#include<math.h>
#define N 110
#define  EPS 1e-10
int n;
struct point
{
double x,y;
};
struct  line
{
point s,t;
}s[N];


double dis(point a,point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
double cross(point a,point b,point c)    //线段和直线相交
{
return (a.x-b.x)*(b.y-c.y)-(a.y-b.y)*(b.x-c.x);
}


bool judge(point a,point b)
{
int i;
if(dis(a,b)<EPS)
return 0;
for(i=0;i<n;i++)
if(cross(a,b,s[i].s)*cross(a,b,s[i].t)>0)
return 0;
return 1;
}


int main()
{
int t,i,flag,j;
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);

for(i=0;i<n;i++)
scanf("%lf%lf%lf%lf",&s[i].s.x,&s[i].s.y,&s[i].t.x,&s[i].t.y);

flag=0;
if(n==1) flag=1;
for(i=0; flag==0 && i<n;i++)
for(j=i+1;flag==0 && j<n;j++)
                if(  judge(s[i].s,s[j].s) ||  judge(s[i].s,s[j].t) || judge(s[i].t,s[j].s) ||  judge(s[i].t,s[j].t)  )
flag=1;
if(flag)
printf("Yes!\n");
else
                    printf("No!\n");
}
return 0;
}