HDU 4266 The Worm in the Apple

三维凸包模版（ps:不知哪位神牛写的。。膜拜）+暴力

#include<cstdio>#include<cmath>#include<algorithm>#define eps 1e-7#define MAXV 1005using namespace std;//三维点struct pt{    double x, y, z;    pt(){}    pt(double _x, double _y, double _z): x(_x), y(_y), z(_z){}    pt operator - (const pt p1){return pt(x - p1.x, y - p1.y, z - p1.z);}    pt operator * (pt p){return pt(y*p.z-z*p.y, z*p.x-x*p.z, x*p.y-y*p.x);}        //叉乘    double operator ^ (pt p){return x*p.x+y*p.y+z*p.z;}                            //点乘};struct _3DCH{    struct fac{        int a, b, c;    //表示凸包一个面上三个点的编号        bool ok;        //表示该面是否属于最终凸包中的面    };    int n;    //初始点数    pt P[MAXV];    //初始点    int cnt;    //凸包表面的三角形数    fac F[MAXV*8]; //凸包表面的三角形    int to[MAXV][MAXV];    double vlen(pt a){return sqrt(a.x*a.x+a.y*a.y+a.z*a.z);}    //向量长度    double area(pt a, pt b, pt c){return vlen((b-a)*(c-a));}    //三角形面积*2    double volume(pt a, pt b, pt c, pt d){return (b-a)*(c-a)^(d-a);}    //四面体有向体积*6    //正：点在面同向    double ptof(pt &p, fac &f){        pt m = P[f.b]-P[f.a], n = P[f.c]-P[f.a], t = p-P[f.a];        return (m * n) ^ t;    }    void deal(int p, int a, int b){        int f = to[a][b];        fac add;        if (F[f].ok){            if (ptof(P[p], F[f]) > eps)                dfs(p, f);            else{                add.a = b, add.b = a, add.c = p, add.ok = 1;                to[p][b] = to[a][p] = to[b][a] = cnt;                F[cnt++] = add;            }        }    }    void dfs(int p, int cur){        F[cur].ok = 0;        deal(p, F[cur].b, F[cur].a);        deal(p, F[cur].c, F[cur].b);        deal(p, F[cur].a, F[cur].c);    }    bool same(int s, int t){        pt &a = P[F[s].a], &b = P[F[s].b], &c = P[F[s].c];        return fabs(volume(a, b, c, P[F[t].a])) < eps && fabs(volume(a, b, c, P[F[t].b])) < eps && fabs(volume(a, b, c, P[F[t].c])) < eps;    }    //构建三维凸包    void construct(){        cnt = 0;        if (n < 4)            return;        fac add;        for (int i = 0; i < 4; i++){            add.a = (i+1)%4, add.b = (i+2)%4, add.c = (i+3)%4, add.ok = 1;            if (ptof(P[i], add) > 0)                swap(add.b, add.c);            to[add.a][add.b] = to[add.b][add.c] = to[add.c][add.a] = cnt;            F[cnt++] = add;        }        for (int i = 4; i < n; i++){            for (int j = 0; j < cnt; j++){                if (F[j].ok && ptof(P[i], F[j]) > eps){                    dfs(i, j);                    break;                }            }        }        int tmp = cnt;        cnt = 0;        for (int i = 0; i < tmp; i++){            if (F[i].ok){                F[cnt++] = F[i];            }        }    }      void solve(){        pt tmp;        double ret = 0.0,min=99999999.9;        scanf("%lf%lf%lf",&tmp.x,&tmp.y,&tmp.z);        for (int i = 0; i < cnt; i++){            ret = fabs(volume(P[F[i].a], P[F[i].b], P[F[i].c],tmp))/area(P[F[i].a], P[F[i].b], P[F[i].c]);            if(ret<min) min=ret;        }        printf("%0.4lf\n",min);    }};_3DCH hull;    //内有大数组，不易放在函数内int main(){    while (~scanf("%d", &hull.n))    {        if(hull.n==0) break;        for (int i = 0; i < hull.n; i++)            scanf("%lf%lf%lf", &hull.P[i].x, &hull.P[i].y, &hull.P[i].z);        hull.construct();        int cssj;        scanf("%d",&cssj);        for(int e=1;e<=cssj;++e)        {         hull.solve();        }    }    return 0;}