hdu 4617 Weapon

http://acm.hdu.edu.cn/showproblem.php?pid=4617

三维几何简单题 多谢高尚博学长留下的模板

代码：

#include <iostream>

#include <cstdio>

#include <algorithm>

#include <cstring>

#include <cmath>

using namespace std;



typedef long long ll;

typedef pair<double,double>ppd;

const double PI = acos(-1.);

const int MAXL = (1 << 18)+100;

const double eps = (1e-9);

const int N=50;

struct point3{double x,y,z;};

struct line3{point3 a,b;};

double r[N];

line3 L[N];

int dcmp(double x)

{

    if(fabs(x)<eps) return 0;

    return x<0?-1:1;

}

point3 xmult(point3 u,point3 v)

{

    point3 ret;

    ret.x=u.y*v.z-v.y*u.z;

    ret.y=u.z*v.x-u.x*v.z;

    ret.z=u.x*v.y-u.y*v.x;

    return ret;

}

double dmult(point3 u,point3 v)

{

    return u.x*v.x+u.y*v.y+u.z*v.z;

}

point3 subt(point3 u,point3 v)

{

    point3 ret;

    ret.x=u.x-v.x;

    ret.y=u.y-v.y;

    ret.z=u.z-v.z;

    return ret;

}

double vlen(point3 p)

{

    return sqrt(p.x*p.x+p.y*p.y+p.z*p.z);

}

double dist(point3 u,point3 v)

{

    return (double)(sqrt((u.x-v.x)*(u.x-v.x)+(u.y-v.y)*(u.y-v.y)+(u.z-v.z)*(u.z-v.z)));

}

double ptoline(point3 p,line3 l)

{

    l.b.x=l.a.x+l.b.x;

    l.b.y=l.a.y+l.b.y;

    l.b.z=l.a.z+l.b.z;

    return vlen(xmult(subt(p,l.a),subt(l.b,l.a)))/dist(l.a,l.b);

}

double linetoline(line3 u,line3 v)

{

    point3 n=xmult(u.b,v.b);

    if(dcmp(vlen(n))==0)

    return ptoline(u.a,v);

    return fabs(dmult(subt(v.a,u.a),n))/vlen(n);

}

point3 pvec(point3 s1,point3 s2,point3 s3)

{

    return xmult(subt(s1,s2),subt(s2,s3));

}



int main()

{

    //freopen("data.in","r",stdin);

    int T;

    scanf("%d",&T);

    while(T--)

    {

        int n;

        scanf("%d",&n);

        for(int i=0;i<n;++i)

        {

            point3 p[3];

            for(int j=0;j<3;++j)

            scanf("%lf %lf %lf",&p[j].x,&p[j].y,&p[j].z);

            L[i].a=p[0];

            L[i].b=pvec(p[0],p[1],p[2]);

            r[i]=dist(p[0],p[1]);

        }

        double k=1e9;

        for(int i=0;i<n;++i)

        for(int j=i+1;j<n;++j)

        {

            //cout<<linetoline(L[i],L[j])<<endl;

            k=min(k,linetoline(L[i],L[j])-r[i]-r[j]);

        }

        if(dcmp(k)<=0)

        printf("Lucky\n");

        else

        printf("%.2lf\n",k);



    }

    return 0;

}