1004

题意：将一些镇子连起来，求最短距离

用kruskal求最小生成树

代码：

#include <iostream>   
#include <algorithm>  
using namespace std;  
const int N = 105;  
int father[N];  
int find(int x)   
{  
    if (x != father[x])  
        father[x] = find(father[x]);  
    return father[x];  
}  
struct edge  
{  
    int x, y, v;  
}e[N*(N - 1) / 2];  
int cmp(edge e1, edge e2)   
{  
    return e1.v<e2.v;  
}  
  
int main()  
{    
    int n;  
    while (cin >> n&&n)  
    {  
        for (int i = 0; i <= n; ++i)  
            father[i] = i;  
       n = n*(n - 1) / 2;  
        for (int i = 0; i<n; i++)  
            cin>>e[i].x>>e[i].y>>e[i].v;  
        sort(e, e + n, cmp);  
        int ans = 0;  
        for (int i = 0; i < n; ++i)  
        {  
            int x = find(e[i].x);  
            int y = find(e[i].y);  
            if (x != y)  
          {     
                ans += e[i].v;  
                father[x] = y;    
            }  
        }  
        cout << ans << endl;  
    }  
    return 0;  
}