Kruskal不用考虑重边，但要考虑是否这棵树是MST，即是否包含所有点 

#include<cstdio>
#include<algorithm>
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
struct Edge{
    int l,r;
    int val;
} edge[20005];
int n,m,x,y,cnt;
ll ans;
int tree[1005];
bool cmp(const Edge x,const Edge y)
{
    return x.val>y.val;
}
int find(int x)
{
    return tree[x]==x?x:tree[x]=find(tree[x]);
}
void Kruskal()
{
    for(int i = 1;i<=n;++i) tree[i] = i;
    for(int i = 0;i<m;++i)
    {
        x = find(edge[i].l);
        y = find(edge[i].r);
        if(x!=y)
        {
            tree[x] = y;
            ans += edge[i].val;
            cnt++;
        }
        if(cnt==n-1) break;
    }
    printf("%lld\n",ans=(cnt==n-1)?ans:-1);//判断所有点都在里面
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        ans = cnt = 0;
        for(int i = 0;i<m;++i)
            scanf("%d%d%d",&edge[i].l,&edge[i].r,&edge[i].val);
        sort(edge,edge+m,cmp);
        Kruskal();
    }
    return 0;
}