HDU 1875（最小生成树）

#include <cstdio>
#include <iostream>
#include <queue>
#include <cmath>
using namespace std;

#define sf scanf
#define pf printf
#define debug printf("!\n")
#define blank printf("\n")
#define mem(a,b) memset(a,b,sizeof(a))

const int MaxN = 110;
const int INF = 1<<27;

int p[MaxN];

int r[MaxN*MaxN],u[MaxN*MaxN],v[MaxN*MaxN];
double w[MaxN*MaxN];

int m,n,vex;

struct point
{
    int x,y;
};

point pt[110];

int find(int x){return p[x]==x?x:p[x]=find(p[x]);}


int cmp(const int a,const int b)
{
    return w[a]<w[b];
}

double kruskal()
{
    double ans = 0;
    int i;

    for(i = 0;i<n;i++) p[i] = i;
    for(i = 0;i<m;i++) r[i] = i;
    
    sort(r,r+m,cmp);

    for(i = 0;i<m;i++)
    {
        int e = r[i];
        int x = find(u[e]);
        int y = find(v[e]);
        if(x!=y)
        {
            ans+=w[e];
            p[x] = y;
            vex++;
        }
    }
    return ans;
}

double getD(point p1 ,point p2)
{
    return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));
}


int main()
{
    int i,j,t;
    sf("%d",&t);
    while(t--)
    {
        mem(u,0);
        mem(v,0);
        mem(w,0);

        m=0;
        vex = 1;
        
        sf("%d",&n);
        for(i = 0;i<n;i++)
        {
            sf("%d%d",&pt[i].x,&pt[i].y);
        }

        for(i = 0;i<n;i++)
        {
            for(j=i+1;j<n;j++)
            {
                double d = getD(pt[i],pt[j]);
                if(d<10 || d>1000)
                {
                    continue;
                }
                u[m] = i;
                v[m] = j;
                w[m++] = d;
            }
        }

        double ans = kruskal();

        if(vex<n)
            pf("oh!\n");
        else
            pf("%.1lf\n",ans*100);
    }

    return 0;
}