zoj 1280 Intersecting Lines(两直线交点)

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
const double epsi=1e-10;
inline int sign(const double &x){
if(x>epsi) return 1;
if(x<-epsi) return -1;
return 0;
}
struct point{
double x,y;
point(double xx=0,double yy=0):x(xx),y(yy){}
point operator -(const point &op2) const{
return point(x-op2.x,y-op2.y);
}
double operator ^(const point &op2) const{
return x*op2.y-y*op2.x;
}
};
inline double sqr(const double &x){
return x*x;
}
inline double mul(const point &p0,const point &p1,const point &p2){
return (p1-p0)^(p2-p0);
}
inline double dis2(const point &p0,const point &p1){
return sqr(p0.x-p1.x)+sqr(p0.y-p1.y);
}
inline double dis(const point &p0,const point &p1){
return sqrt(dis2(p0,p1));
}
inline int cross(const point &p1,const point &p2,const point &p3,const point &p4,point &p){
double a1=mul(p1,p2,p3),a2=mul(p1,p2,p4);
if(sign(a1)==0&&sign(a2)==0) return 2;//重叠
if(sign(a1-a2)==0) return 0;
p.x=(a2*p3.x-a1*p4.x)/(a2-a1);
p.y=(a2*p3.y-a1*p4.y)/(a2-a1);    //利用公式计算交点
return 1;
}
point p1,p2,p3,p4,p;
int main()
{
int test=0;
scanf("%d",&test);
printf("INTERSECTING LINES OUTPUT\n");
while(test--){
scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&p1.x,&p1.y,&p2.x,&p2.y,&p3.x,&p3.y,&p4.x,&p4.y);
int m=cross(p1,p2,p3,p4,p);
if(m==0) printf("NONE\n");
else if(m==2) printf("LINE\n");
else  printf("POINT %.2lf %.2lf\n",p.x,p.y);
}
printf("END OF OUTPUT\n");
return 0;
}