http://acm.hdu.edu.cn/webcontest/contest_showproblem.php?pid=1004&ojid=2&cid=963&hide=0

#include<iostream>
#include<cmath>
#define N 101
#define M 99999999.0
#define  FOR(i,s,t) for(int i=(s);i<=(t);++i)
#include<cstdio>
using namespace std;
double map

;
double  dist
;
bool visit
;
struct point{ double x,y;
}aa
;
int n,tot;
inline double distan(point& a,point& b )
{      return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)); }

void prim()
{ FOR(i,1,n)
{  dist[i]=M;
visit[i]=true;
}
int now=1;
dist[now]=0.0;
visit[now]=false;
double ans=0.0;
FOR(i,1,n)
{  ans+=dist[now];
FOR(j,1,n)
if(visit[j]&&dist[j]>map[now][j])
dist[j]=map[now][j];
double minx=M;
FOR(j,1,n)
if(visit[j]&&minx>dist[j])
minx=dist[now=j];
visit[now]=false;
}
if(tot) cout<<endl; 这个地方最容易出错，，，，，，
printf("Case #%d:\nThe minimal distance is: %.2lf\n",++tot,ans);
}
int main()
{    int tot=0;
while(~scanf("%d",&n)!=EOF&&n)
{  for(int i=1;i<=n;i++)
for(int j=1;j<=n;++j)
map[i][j]=M;
for(int i=1;i<=n;i++)
~scanf("%lf%lf",&aa[i].x,&aa[i].y);
for(int i=1;i<n;++i)
for(int j=i+1;j<=n;++j)
map[i][j]=map[j][i]=distan(aa[i],aa[j]);
prim();
} return 0;
}