Jack Straws POJ - 1127

3

#include <iostream>
#include <cmath>

using namespace std;

const int maxn = 100;
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&&
    sgn((l2.s-l1.s)^(l2.e-l1.s))*sgn((l2.s-l1.e)^(l2.e-l1.e))<=0;
}

bool inter(Line l1,Line l2) {  
    return     
    max(l1.s.x,l1.e.x) >= min(l2.s.x,l2.e.x) &&     
    max(l2.s.x,l2.e.x) >= min(l1.s.x,l1.e.x) &&     
    max(l1.s.y,l1.e.y) >= min(l2.s.y,l2.e.y) &&     
    max(l2.s.y,l2.e.y) >= min(l1.s.y,l1.e.y) &&     
    sgn((l2.s-l1.e)^(l1.s-l1.e))*sgn((l2.e-l1.e)^(l1.s-l1.e)) <= 0 &&     
    sgn((l1.s-l2.e)^(l2.s-l2.e))*sgn((l1.e-l2.e)^(l2.s-l2.e)) <= 0; 
}

Point p[maxn];
Line line[maxn];
int num[maxn];

int find(int m)
{
    while(m!=num[m])
        m=num[m];
    return m;
}
void Union(int x,int y)
{
    int _x=find(x);
    int _y=find(y);
    if(_x>_y)
        num[_x]=_y;
    else
        num[_y]=_x;
}
int main()
{
    int n;
    while(1)
    {
        cin>>n;
        if(n==0)
            break;
        for(int i=1;i<=n;i++)
        {
            double x1,y1,x2,y2;
            cin>>x1>>y1>>x2>>y2;
            line[i]=Line(Point(x1,y1),Point(x2,y2));
        }
        for(int i=0;i<maxn;i++)
            num[i]=i;
        for(int i=1;i<=n;i++)
        {
            for(int j=i+1;j<=n;j++)
            {
                if(inter(line[i],line[j]))
                {
                    Union(i,j);
                }
            }
        }
        while(1)
        {
            int a,b;
            cin>>a>>b;
            if(a==0&&b==0)
                break;
            if(a==b)
            {
                cout<<"CONNECTED"<<endl;
                continue;
            }
            int x,y;
            if(a>b)
            {
                x=a;
                y=b;
            }
            else
            {
                x=b;
                y=a;
            }
            if(find(a)==find(b))
                cout<<"CONNECTED"<<endl;
            else
                cout<<"NOT CONNECTED"<<endl;
        }
    }
    return 0;
}