poj1269+判断线的交点

poj1269+判断线的交点

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
double INF = 1e20;
double EPS = 1e-8; 
bool (double x) {   return -EPS < x && x < EPS; }
struct CVector{
	double x,y;
	CVector (){}
	CVector (double tx,double ty){
		x=tx;y=ty;
	}
	CVector operator +(const CVector &b)const
	{
		return CVector(x+b.x,y+b.y);
	}
	CVector operator -(const CVector &b)const
	{
		return CVector(x-b.x,y-b.y);
	}
	double operator ^(const CVector &b)const
	{
		return x*b.y-y*b.x;
	}
	double operator *(const CVector &b)const
	{//点积
		return x*b.x+y*b.y;
	}
	CVector operator *(const double k)const
	{
		return CVector(k*x,k*y);
	}
};
#define  Point CVector
struct Line{
	Point a,b;
	Line(){}
    Line(Point s,Point e)
    {
        a = s;b = e;
    }
};
double area(CVector a,CVector b)
{
	return (a^b)/2;
}
double onLine(Point p,Line l)//就是判断点是否在直线上就行
{
	return fabs((p-l.a) ^ (l.b-l.a));
}
Point intersect(Line l, Line m, int &t)
{
	double x = area(m.a-l.a,l.b-l.a);//运用面积来求
	double y = area(l.b-l.a,m.b-l.a);
	//printf("%lf %lfn",x,y);
	if(IsZero(x + y))
	{
		if(IsZero(onLine(l.a, m))) t =1; //两平行线的距离  = 点到另一直线的距离
		else t =-1;    //平行
		return Point(-1100,-1100);
	}
	t=0;
	return m.a+(m.b-m.a)*(x/(x + y));
} //即便线段 l.a->l.b和 m.a->m.b没交点，也适用
int main()
{
	int n,t;
	scanf("%d",&n);
	printf("INTERSECTING LINES OUTPUTn");
	Point p,q;
	for(int i=1;i<=n;i++)
	{
		scanf("%lf%lf%lf%lf",&p.x,&p.y,&q.x,&q.y);
		Line l1(p,q);
		scanf("%lf%lf%lf%lf",&p.x,&p.y,&q.x,&q.y);
		Line l2(p,q);
		Point tmp=intersect(l1,l2,t);
		if(t==1) printf("LINEn");
		else if(t==-1) printf("NONEn");
		else
			printf("POINT %.2lf %.2lfn",tmp.x,tmp.y);
	}
	printf("END OF OUTPUTn");
	return 0;
}