POJ 1269 Intersecting Lines 判断两直线关系

用的是初中学的方法

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#define eps 1e-8
using namespace std;


struct Point
{
    double x,y;
    Point() {};
    Point(double xx,double yy)
    {
        x=xx;
        y=yy;
    }
}ans;

int getCross(Point p1,Point p2,Point q1,Point q2)
{
    double k1=(p1.y-p2.y)/(p1.x-p2.x);
    double k2=(q1.y-q2.y)/(q1.x-q2.x);
    double b1=p1.y-k1*p1.x;
    double b2=q1.y-k2*q1.x;
    if(p1.x==p2.x && q1.x==q2.x) return p1.x==q1.x? 1:-1;
    if(p1.x==p2.x)
    {
        ans=Point(p1.x,k2*p1.x+b2);
        return 0;
    }
    if(q1.x==q2.x)
    {
        ans=Point(q1.x,k1*q1.x+b1);
        return 0;
    }
    if(fabs(k1-k2)<eps) return fabs(b1-b2)<eps? 1:-1;
    ans.x=(b2-b1)/(k1-k2);
    ans.y=k1*ans.x+b1;
    return 0;
}

int main()
{
//    freopen("in.txt","r",stdin);
    int t;
    scanf("%d",&t);
    Point pot[4];
    puts("INTERSECTING LINES OUTPUT");
    while(t--)
    {
        double x,y;
        for(int i=0; i<4; i++)
        {
            scanf("%lf%lf",&x,&y);
            pot[i]=Point(x,y);
        }
        int tmp=getCross(pot[0],pot[1],pot[2],pot[3]);
        if(tmp==-1) puts("NONE");
        else if(tmp==1) puts("LINE");
        else printf("POINT %.2f %.2f
",ans.x,ans.y);
    }
    puts("END OF OUTPUT");
    return 0;
}