【bzoj1027】合金

【bzoj1027】合金

分析

数形结合+计算几何+Floyd最小环。

http://blog.csdn.net/popoqqq/article/details/40539273

虽然这样占大家的很不好，但是我的确需要这么做。

小结

（1）最小环的写法

（2）凸包的一种简易算法

RT。

（3）关于计算几何的练习

通过做这道题，计算几何的模板也熟悉了一些。

计算几何如何调试？

这个么...好像只能瞪眼法了。

代码

#include <cstdio>
#include <climits>
#include <cmath>
#include <algorithm>
using namespace std;

#define rep(i,a,b) for (int i=(a);i<=(b);i++)

const int M=512;
const int N=512;
const int MAX=INT_MAX>>1;
const double EPS=1e-15;

int cmp(double x);

int m,n;
struct point
{
    double x,y;
    point(double _x=0,double _y=0) {
        x=_x,y=_y;
    }
    friend point operator - (point a,point b) {
        return point(a.x-b.x,a.y-b.y);
    }
    friend point operator * (point a,point b) {
        return point(a.x*b.x,a.y*b.y);
    }
    friend int operator == (point a,point b) {
        return !cmp(a.x-b.x)&&!cmp(a.y-b.y);
    }
    friend int operator != (point a,point b) {
        return !(a==b);
    }
}mer[M],prd[N];

int f[M][M];
int res;

void Init(void) {
    scanf("%d%d",&m,&n);
    rep(i,1,m) {
        double x,y; scanf("%lf%lf%*lf",&x,&y);
        mer[i]=point(x,y);
    }
    rep(i,1,n) {
        double x,y; scanf("%lf%lf%*lf",&x,&y);
        prd[i]=point(x,y);
    }
}

int cmp(double x)
{
    if(fabs(x)<EPS)  return 0;
    return x>0?1:-1;
}

double det(point a,point b) {
    return a.x*b.y-a.y*b.x;
}

int Left(point k,point a,point b) {
    double t=det(b-a,k-a);
    return t>0;
}
int On(point k,point a,point b) {
    if (cmp(det(k-a,b-a))!=0) return 0;
    if (!(cmp(min(a.x,b.x)-k.x)<=0&&cmp(k.x-max(a.x,b.x))<=0)) return 0;
    if (!(cmp(min(a.y,b.y)-k.y)<=0&&cmp(k.y-max(a.y,b.y))<=0)) return 0;
    return 1;
}

/*
bool On(const point &a,const point &b,const point &c) {
    return !cmp(det(a-b,c-b))&&cmp((a.x-b.x)*(a.x-c.x))<=0&&cmp((a.y-b.y)*(a.y-c.y))<=0;
}
*/

int Check(point a,point b) {
    rep(i,1,n) {
        int t1=Left(prd[i],a,b);
        int t2=On(prd[i],a,b);
        if (!t1&&!t2) return 0;
    }
    return 1;
}

void MakeGraph(void) {
    rep(i,1,m) rep(j,1,m) f[i][j]=MAX;
    rep(i,1,m) rep(j,1,m)
        if (Check(mer[i],mer[j]))
            f[i][j]=1;
}

int Floyd(void) {
    rep(i,1,m) {
        int mrk=1;
        rep(j,1,n) if (mer[i]!=prd[j]) {
            mrk=0;
            break;
        }
        if (mrk) return 1;
    }

    rep(i,1,m) rep(j,1,m) {
        int mrk=1;
        rep(k,1,n)
            if (!On(prd[k],mer[i],mer[j])) {
                mrk=0;
                break;
            }
        if (mrk) return 2;
    }

    /*
    rep(i,1,m) {
        rep(j,1,m)
            if (f[i][j]!=MAX)
                printf("%d ",f[i][j]);
            else printf("0 ");
        printf("\n");
    }
    */

    int ans=MAX;
    rep(k,1,m) rep(i,1,m) rep(j,1,m)
        f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
    rep(i,1,m) ans=min(ans,f[i][i]);
    return ans!=MAX?ans:-1;
}

int main(void) {
    #ifndef ONLINE_JUDGE
    freopen("bzoj1027.in","r",stdin);
    freopen("bzoj1027.out","w",stdout);
    #endif

    Init();
    MakeGraph();

    res=Floyd();
    printf("%d\n",res);

    return 0;
}