prim模板题

题目链接：http://acm.hrbeu.edu.cn/index.php?act=problem&id=1223

 #include <cstdio>
 #include <cmath>
 #include <algorithm>
 #include <iostream>
 #include <cstring>
 #include <queue>
 #include <vector>

 #define maxn 115
 using namespace std;

 const int INF = 0x3f3f3f;

 struct Point{
     double x,y;
     bool operator < (const Point & rh) const{
         return y < rh.y  || (y == rh.y && x < rh.x);
     }
 }p[maxn];
 int n;
 double ans;
 double G[maxn][maxn];

 double calculate(int i,int j){
     double xx = p[j].x - p[i].x;
     double yy = p[j].y - p[i].y;
     return sqrt(xx*xx + yy*yy);
 }

 void prim(){
     bool vis[maxn];
     double lowdist[maxn];
     double mindist;
     memset(vis,,sizeof(vis));
     for(int i=;i<=n;i++) lowdist[i]=INF;
     int point;
     int s=;
     vis[s] =true;
     int num=;
     while(true){
         if(num == n) break;
         vis[s]=true;
         mindist = INF;
         for(int i=;i<=n;i++){
             if(!vis[i] && lowdist[i] > G[s][i]){
                 lowdist[i] = G[s][i];
             }
             if(!vis[i] && mindist  > lowdist[i]){
                 mindist=lowdist[i];
                 point = i;
             }
         }
         s = point;
         ans += mindist;
         num++;
     }
     return;
 }
 int main()
 {
 //    if(freopen("input.txt","r",stdin)== NULL)  {printf("Error\n"); exit(0);}

     while(scanf("%d",&n)== && 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++){
              G[i][j] = G[j][i] = calculate(i,j);
            }
            ans = ;
            //print();
         prim();
         printf("%.2lf\n",ans);
     }
 }