poj1269

基础计算几何

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//zju1280

#include <iostream>

#include <cstdio>

using namespace std;



struct Point

{

    double    x,y;

};



class Line

{

public:

    Point    pointa,pointb,pointk;

    void    makeline(Point pointa,Point pointb);

};



void Line::makeline(Point a,Point b)

{

    pointa=a;

    pointb=b;

    pointk.x=pointa.x-pointb.x;

    pointk.y=pointa.y-pointb.y;

    if (pointk.x<0)

    {

        pointk.x=-pointk.x;

        pointk.y=-pointk.y;

    }

}





int        T;

Line    line1,line2;



void init()

{

    Point    a,b;



    cin>>a.x>>a.y>>b.x>>b.y;

    line1.makeline(a,b);

    cin>>a.x>>a.y>>b.x>>b.y;

    line2.makeline(a,b);

}



int    cross(Line line1,Line line2)

{

    if (!(line1.pointk.x*line2.pointk.y==line1.pointk.y*line2.pointk.x))

        return 0;                                                                                            //相交

    if (line1.pointk.y*(line2.pointb.x-line1.pointb.x)==(line2.pointb.y-line1.pointb.y)*line1.pointk.x)

        return 1;                                                                                            //重合

    return 2;                                                                                                //平行

}





double xmulti(Point p0, Point p1, Point p2)

{

    return ((p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y));

}



Point crosspoint(Line line1,Line line2)

{

    double s1 = xmulti(line1.pointa, line1.pointb, line2.pointa);

    double s2 = xmulti(line1.pointa, line1.pointb, line2.pointb);

    Point ret;

    ret.x = (s1 * line2.pointb.x - s2 * line2.pointa.x) / (s1 - s2);

    ret.y = (s1 * line2.pointb.y - s2 * line2.pointa.y) / (s1 - s2);

    return ret;

}



void work()

{

    int        ans;

    Point    pointans;



    ans=cross(line1,line2);

    switch (ans)

    {

    case    0    :

        pointans=crosspoint(line1,line2);

        printf("POINT %.2f %.2f\n",pointans.x,pointans.y);

        break;

    case    1    :

        cout<<"LINE\n";

        break;

    case    2    :

        cout<<"NONE\n";

        break;

    }

}



int main()

{

//    freopen("t.txt","r",stdin);

    cin>>T;

    cout<<"INTERSECTING LINES OUTPUT\n";

    while (T--)

    {

        init();

        work();

    }

    cout<<"END OF OUTPUT\n";

    return 0;

}