Segments POJ - 3304

/*
判断直线与线段的相交
wa在没有用sgn！！！！
暑假训练 2
*/
#include <iostream>
#include <cmath>

using namespace std;

const int maxn = 500;
const double eps = 1e-8;

int sgn(double x)
{
    if(fabs(x)<eps)
        return 0;
    if(x<0)
        return -1;
    else
        return 1;
}
struct Point
{
    double x,y;
    Point(){}
    Point(double _x,double _y)
    {
        x=_x;
        y=_y;
    }
    Point operator -(const Point &b)const
    {
        return Point(x-b.x,y-b.y);
    }
    double operator ^(const Point &b)const
    {
        return x*b.y-y*b.x;
    }
    double operator *(const Point &b)const
    {
        return x*b.x+y*b.y;
    }
};

struct Line
{
    Point s,e;
    Line(){}
    Line(Point _s,Point _e)
    {
        s=_s;
        e=_e;
    }
};

bool OnSeg(Line l1,Line l2)
{
    return
    sgn((l1.s-l2.s)^(l1.e-l2.s))*sgn((l1.s-l2.e)^(l1.e-l2.e))<=0;
}

double dist(Point a,Point b)
{
    return sqrt((a-b)*(a-b));
}
Point p[maxn];
Line line[maxn];
int main()
{
    int n;
    cin>>n;
    while(n--)
    {
        int m;
        cin>>m;
        int cont=0;
        int lcont=0;
        for(int i=0;i<m;i++)
        {
            cin>>p[cont].x>>p[cont].y;
            cont++;
            cin>>p[cont].x>>p[cont].y;
            cont++;
            line[lcont]=Line(p[cont-1],p[cont-2]);
            lcont++;
        }
        int jump=0;
        for(int i=0;i<cont;i++)
        {
            if(jump==1)
                break;
            for(int j=i+1;j<cont;j++)
            {
                if(sgn(dist(p[i],p[j]))==0)
                    continue;
                Line sline =Line(p[i],p[j]);
                int fl=0;
                for(int z=0;z<lcont;z++)
                {
                    if(!OnSeg(sline,line[z]))
                    {
                        fl=1;
                        break;
                    }
                }
                if(fl==0)
                {
                    jump=1;
                    break;
                }
            }
        }
        if(jump==1)
            cout<<"Yes!"<<endl;
        else
            cout<<"No!"<<endl;
    }
    return 0;
}