求直线交点还是要推一个公式的。。
见博客https://blog.csdn.net/u013050857/article/details/40923789
还要学一下向量的定点比分法
另外poj精度好像卡的厉害，zoj1280就没啥问题
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std; const double esp = 1e-;
const double inf = 1e20;
const double pi = acos(-1.0);
const int maxp = ; int sgn(double x){
if(fabs(x) < esp)return ;
if(x < )return -;
else return ;
}
inline double sqr(double x){return x*x;} struct Point{
double x,y;
Point(){}
Point(double _x,double _y):x(_x),y(_y){}
void input(){scanf("%lf%lf",&x,&y);}
void output(){printf("%.2lf %.2lf\n",x,y);}
bool operator==(Point b)const {
return sgn(x-b.x)== && sgn(y-b.y)==;
}
bool operator < (Point b)const {//判左下
if( sgn(x-b.x)== ) //横坐标相等
return sgn(y-b.y)<;
return x<b.x;
}
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;
}
double len(){
return hypot(x,y);
}
double len2(){
return x*x+y*y;
}
double distance(Point p){
return hypot(x-p.x,y-p.y);
}
Point operator +(const Point &b)const {
return Point(x+b.x,y+b.y);
}
Point operator *(const double &k)const {
return Point(x*k,y*k);
}
Point operator /(const double &k)const {
return Point(x/k,y/k);
}
double rad(Point a,Point b){
Point p=*this;
return fabs(atan2( fabs((a-p)^(b-p)),(a-p)*(b-p) ));
}
Point trunc(double r){
double l=len();
if(!sgn(l))return *this;
r/=l;
return Point(x*r,y*r);
}
Point rotleft(){
return Point(-y,x);
}
Point rotright(){
return Point(y,-x);
}
Point rotate(Point p,double angle){
Point v=(*this)-p;
double c=cos(angle),s=sin(angle);
return Point(p.x+v.x*c-v.y*s, p.y+v.x*s+v.y*c);
}
};
struct Line{
Point s,e;
Line(){}
Line(Point s,Point e):s(s),e(e){}
bool operator ==(Line v){
return (s==v.s) && (e==v.e);
}
Line(Point p,double angle){
s=p;
if(sgn(angle-pi/)==)
e=s+Point(,);
else e=s+Point(,tan(angle));
}
Line(double a,double b,double c){
if(sgn(a)==){
s=Point(,-c/b);
e=Point(,-c/b);
}
else if(sgn(b)==){
s=Point(-c/a,);
e=Point(-c/a,);
}
else {
s=Point(,-c/b);
e=Point(,(-c-a)/b);
}
}
void input(){
s.input();
e.input();
}
void adjust(){
if(e<s)swap(e,s);
}
double length(){
return s.distance(e);
}
double angle(){
double k=atan2(e.y-s.y,e.x-s.x);
if(sgn(k)<)k+=pi;
if(sgn(k-pi)==) k-=pi;
return k;
}
int relation(Point p){
int c=sgn((p-s)^(e-s));
if(c<)return ;
else if(c>)return ;
else return ;
}
bool pointonseg(Point p){
return sgn((p-s)^(e-s))== && sgn((p-s)*(p-e))<=;
}
bool parallel(Line v){
return sgn((e-s)^(v.e-v.s))==;
}
int segcrossseg(Line v){
int d1=sgn((e-s)^(v.s-s));
int d2=sgn((e-s)^(v.e-s));
int d3=sgn((v.e-v.s)^(s-v.s));
int d4=sgn((v.e-v.s)^(e-v.s));
if( (d1^d2)==- && (d3^d4)==-) return ;
return (d1== && sgn((v.s-s)*(v.s-e))<=) ||
(d2== && sgn((v.e-s)*(v.e-e))<=) ||
(d3== && sgn((s-v.s)^(s-v.e))<=) ||
(d4== && sgn((e-v.s)^(e-v.e))<=);
}
int linecrossseg(Line v){
int d1=sgn((e-s)^(v.s-s));
int d2=sgn((e-s)^(v.e-s));
//cout<<(d1^d2)<<'\n';
if((d1^d2)==-)return ;
return d1== || d2==;
}
int linecrossline(Line v){
if((*this).parallel(v))
return v.relation(s)==;
return ;
}
Point crosspoint(Line v){
double a1=(v.e-v.s)^(s-v.s);//面积
double a2=(v.e-v.s)^(e-v.s);
return Point((s.x*a2-e.x*a1)/(a2-a1),
(s.y*a2-e.y*a1)/(a2-a1));
}
double dispointtoline(Point p){
return fabs((p-s)^(e-s))/length();
}
double dispointtoseg(Point p){
if(sgn((p-s)*(e-s))< || sgn((p-e)*(s-e))<)
return min(p.distance(s),p.distance(e));
return dispointtoline(p);
}
double dissegtoseg(Line v){
return min(min(dispointtoseg(v.s),dispointtoseg(v.e)),
min(v.dispointtoline(s),v.dispointtoline(e)));
}
Point lineprog(Point p){//s+vt
return s+( ((e-s)*((e-s)*(p-s)))/(e-s).len2() );
}
Point symmetrypoint(Point p){
Point q=lineprog(p);
return Point(*q.x-p.x,*q.y-p.y);
}
}; //判两直线是否相交
int main(){
int t;cin>>t;
puts("INTERSECTING LINES OUTPUT");
for(int tt=;tt<=t;tt++){
double x1,y1,x2,y2;
cin>>x1>>y1>>x2>>y2;
Line line1=Line(Point(x1,y1),Point(x2,y2));
cin>>x1>>y1>>x2>>y2;
Line line2=Line(Point(x1,y1),Point(x2,y2));
if(line1.linecrossline(line2)==)
puts("NONE");
else if(line1.linecrossline(line2)==)
puts("LINE");
else if(line1.linecrossline(line2)==){
Point p=line1.crosspoint(line2);
printf("POINT %.2lf %.2lf\n",p.x,p.y);
}
}
puts("END OF OUTPUT");
}