poj 1287 Networking

#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstdio>
using namespace std;
#define maxn 1100
int par[maxn];
int n,m;
int len;
int cnt;
struct node
{
    int x;
    int y;
    int w;
};
node e[maxn * (maxn - 1) / 2];
int cmp(const node &a , const node &b)
{
    return a.w < b.w;
};
void init()
{
    for(int i = 1; i <= n+5; i++)
        par[i] = i;
    len = 0;
    cnt = 0;
}
int Find(int x)
{
    int k,j,r;
    r = x;
    while(par[r] != r)
        r = par[r];
    k = x;
    while(k != r)
    {
        j = par[k];
        par[k] = r;
        k = j;
    }
    return r;
}
int Merge(int x,int y)
{
    int a = Find(x);
    int b = Find(y);
    if(a != b)
    {
        par[a] = par[b];
        return 1;
    }
    return 0;
}


void make()
{
    for(int i = 0; i < m; i++)
        scanf("%d%d%d",&e[i].x,&e[i].y,&e[i].w);
    sort(e,e+m,cmp);
    for(int i = 0; i < m; i++)
    {
        if(Merge(e[i].x,e[i].y))
        {
            len += e[i].w;
            cnt++;
        }
        if(cnt == n - 1) break;
    }
}
int main()
{
    freopen("input.txt","r",stdin);
    while(scanf("%d%d",&n,&m) && n)
    {
        if(m == 0) { printf("0
"); continue; }
        init();
        make();
        if(cnt == n-1) printf("%d
",len);
        else printf("-1
");
    }

    return 0;
}