直线相交 POJ 1269

// 直线相交 POJ 1269

// #include <bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <math.h>
using namespace std;
#define LL long long
typedef pair<int,int> pii;
const double inf = 123456789012345.0;
const LL MOD =100000000LL;
const int N =1e4+10;
#define clc(a,b) memset(a,b,sizeof(a))
const double eps = 1e-8;
void fre() {freopen("in.txt","r",stdin);}
void freout() {freopen("out.txt","w",stdout);}
inline int read() {int x=0,f=1;char ch=getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch=getchar();}while(ch>='0'&&ch<='9') {x=x*10+ch-'0';ch=getchar();}return x*f;}

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;
    }
    pair<int,Point> operator & (const Line &b) const{
        Point res=s;
        if(sgn((s-e)^(b.s-b.e))==0){
            if(sgn((s-b.e)^(b.s-b.e))==0) 
                return make_pair(0,res);
            else  return make_pair(1,res);
        }
        double t=((s-b.s)^(b.s-b.e))/((s-e)^(b.s-b.e));
        res.x+=(e.x-s.x)*t;
        res.y+=(e.y-s.y)*t;
        return make_pair(2,res);
    }
};

int main(){
    int T;
    scanf("%d",&T);
    double x1,x2,x3,x4,y1,y2,y3,y4;
    printf("INTERSECTING LINES OUTPUT
");
    while(T--){
        scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);
        Line line1 = Line(Point(x1,y1),Point(x2,y2));
        Line line2 = Line(Point(x3,y3),Point(x4,y4));
        pair<int,Point> ans=line1 & line2;
        if(ans.first==0) printf("LINE
");
        else if(ans.first==1) printf("NONE
");
        else printf("POINT %.2f %.2f
",ans.second.x,ans.second.y);
    }
    printf("END OF OUTPUT
");
    return 0;
}