uva 10034 Problem A: Freckles

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=975

最小生成树。

 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #define maxn 1000
 using namespace std;
 const double inf=(double)(<<);

 int t,n;
 struct node
 {
     double x,y;
 }p[maxn];
 bool vis[maxn];
 double dis[maxn];
 double g[maxn][maxn];
 double ans;

 double sqr(double x)
 {
     return x*x;
 }

 void prim()
 {
     memset(vis,false,sizeof(vis));
     for(int i=; i<=n; i++) dis[i]=g[][i];
     dis[]=;
     vis[]=true;
     for(int i=; i<n; i++)
     {
         double m=inf;
         int x;
         for(int y=; y<=n; y++) if(!vis[y]&&dis[y]<m) m=dis[x=y];
         ans+=m;
         vis[x]=true;
         for(int y=; y<=n; y++) if(!vis[y]&&dis[y]>g[x][y]) dis[y]=g[x][y];
     }
 }

 int main()
 {
     scanf("%d",&t);
     while(t--)
     {
         scanf("%d",&n);
         for(int i=; i<=n; i++)
         {
             scanf("%lf%lf",&p[i].x,&p[i].y);
         }
         for(int i=; i<=n; i++)
         {
             for(int j=i; j<=n; j++)
             {
                 if(i==j) g[i][j]=;
                 else
                 g[i][j]=g[j][i]=sqrt(sqr(p[i].x-p[j].x)+sqr(p[i].y-p[j].y));
             }
         }
         ans=;
         prim();
         printf("%.2lf\n",ans);
         if(t) printf("\n");
     }
     return ;
 }