poj1287 kruskal

#include<cstdio>
#include<cstdlib>
#include<iostream>
#define N 60
using namespace std;
struct node
{
    int x,y;
    int len;
} city[2600];
typedef struct node NODE;
int n,m,pre[N];
int cmp(const void *a,const void *b)
{
    return ((NODE*)a)->len - ((NODE*)b)->len;
}
int find( int x )
{
    while( x!= pre[x] )
        x = pre[x];
    return x;
}
void kruskal()
{
    int i,a,b,sum = 0;
    qsort(city,m,sizeof(NODE),cmp);
    for(i=1; i<=n; i++)
        pre[i] = i;
    for(i=0; i<m; i++)
    {
        a = find(city[i].x);
        b = find(city[i].y);
        if( a!= b)
        {
            sum += city[i].len;
            pre[b] = a;
        }
    }
    cout << sum << endl;
}
int main()
{
    //freopen("3.txt","r",stdin);
    while( cin>>n && n )
    {
        cin>>m;
        for(int i=0; i<m; i++)
            cin >> city[i].x >> city[i].y >> city[i].len;
        kruskal();
    }
    return 0;
}