参考答案：

#include<iostream>
#include<cstring>

using namespace std;

const int M = 200010, N = 1010;
int g[N][N];
int st[N], dis[N];
int n, m, res;

bool prim()
{
    memset(dis, 0x3f, sizeof(dis));

    for (int i = 0; i < n; ++i)
    {
        int t = -1;
        for (int j = 1; j <= n; ++j)
            if (!st[j] && (t == -1 || dis[j] < dis[t]))
                t = j;
        if (i && dis[t] == 0x3f3f3f3f) return false;
        if (i) res += dis[t];
        for (int j = 1; j <= n; ++j)
            dis[j] = min(dis[j], g[t][j]);
        st[t] = 1;
    }

    return true;
}
int main()
{
    cin >> n >> m;

    memset(g, 0x3f, sizeof(g));

    for (int i = 1; i <= m; ++i)
    {
        int a, b, c;
        cin >> a >> b >> c;
        g[a][b] = g[b][a] = min(g[a][b], c);
    }

    bool t = prim();

    if (t) cout << res;
    else cout << "Not exist";

    return 0;
}