POJ-1269 Intersecting Lines
题意:判断两条直线相交,平行还是重合
#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct Point{
double x,y;
Point(double xx=0,double yy=0){
x=xx,y=yy;
}
}s1,s2,t1,t2;
struct Vector{
double x,y;
Vector(double xx=0,double yy=0){
x=xx,y=yy;
}
};
int t;
int dcmp(double x){return fabs(x)<1e-9?0:(x>0?1:-1);}
Vector operator - (Point a,Point b){return Vector(a.x-b.x,a.y-b.y);}
Vector operator * (double p,Vector a){return Vector(a.x*p,a.y*p);}
Point operator + (Point a,Vector b){return Point(a.x+b.x,a.y+b.y);}
double operator * (Vector a,Vector b){return a.x*b.y-a.y*b.x;}
double len(Vector a){return sqrt(a.x*a.x+a.y*a.y);}
double distl(Point p,Point a,Point b){
Vector v1=b-a,v2=p-a;
return v1*v2/len(v1);
}
Point fla(Point a,Point b,Point c,Point d){
Vector v1=b-a,v2=d-c,v3=a-c;
return a+v2*v3/(v1*v2)*v1;
}
int check(Point a,Point b,Point c,Point d){
Vector x=b-a,y=d-c;
Vector v1=c-a,v2=d-a;
int ax=dcmp(x*v1),bx=dcmp(x*v2);
v1=a-c,v2=b-c;
int ay=dcmp(y*v1),by=dcmp(y*v2);
if((ax==bx&&ax==0)||(ay==by&&ay==0)) return 0;
if((ax==bx&&(distl(c,a,b)==distl(d,a,b)))||(ay==by&&distl(a,c,d)==distl(b,c,d))) return 1;
return 2;
}
int main(){
scanf("%d",&t);
printf("INTERSECTING LINES OUTPUT\n");
while(t--){
scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&s1.x,&s1.y,&t1.x,&t1.y,&s2.x,&s2.y,&t2.x,&t2.y);
int x=check(s1,t1,s2,t2);
if(!x) printf("LINE\n");
if(x==1) printf("NONE\n");
if(x==2){
Point b=fla(s1,t1,s2,t2);
printf("POINT %.2lf %.2lf\n",b.x,b.y);
}
}
printf("END OF OUTPUT\n");
return 0;
}