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,0,sizeof(vis));
    for(int i=1;i<=n;i++) lowdist[i]=INF;
    int point;
    int s=1;
    vis[s] =true;
    int num=1;  
    while(true){
        if(num == n) break;
        vis[s]=true;
        mindist = INF;
        for(int i=1;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
"); exit(0);}

    while(scanf("%d",&n)==1 && n){
        for(int i=1;i<=n;i++){
            scanf("%lf%lf",&p[i].x,&p[i].y);
        }
        for(int i=1;i<=n;i++)
           for(int j=i+1;j<=n;j++){
             G[i][j] = G[j][i] = calculate(i,j);  
           }
           ans = 0;
           //print();
        prim();
        printf("%.2lf
",ans);
    }
}