【题目链接】http://www.ifrog.cc/acm/problem/1000

【解题方法】裸的最小生成树。

【AC 代码】

//
//Created by just_sort 2016/9/25 13:42
//Copyright (c) 2016 just_sort.All Rights Reserved
//

#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
typedef long long LL;
const double inf = 1e18;
int n;
double g[55][55];
double dis[55];
bool vis[55];
struct Point{
    double x,y,z;
    void read(){
        scanf("%lf%lf%lf",&x,&y,&z);
    }
}p[55];
double getdis(Point a,Point b){
    return  sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z));
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        for(int i=1; i<=n; i++) p[i].read();
        for(int i=1; i<=n; i++) dis[i] = inf;
        for(int i=1; i<=n; i++) vis[i] = false;
        for(int i=1; i<=n; i++){
            for(int j=1; j<=n; j++){
                if(i==j) g[i][j] = inf;
                else g[i][j] = getdis(p[i],p[j]);
            }
        }
        double ans = 0;
        dis[1] = 0;
        for(int i=1; i<=n; i++){
            int mark;double minn=inf;
            for(int j=1; j<=n; j++){
                if(!vis[j] && dis[j]<minn){
                    minn = dis[j];
                    mark = j;
                }
            }
            vis[mark] = 1;
            ans += dis[mark];
            for(int j=1; j<=n; j++){
                if(!vis[j] && g[mark][j]<dis[j]){
                    dis[j] = g[mark][j];
                }
            }
        }
        printf("%.2f\n",ans);
    }
    return 0;
}