最小生成树算法，用的prim，代码有点臃肿，超时了，后面再修改

unordered_set<int>visited;
unordered_set<int>q;
int n, m;
int dis ;
unordered_map<int, vector<vector<int>>>m1;

void dfs()
{
    while (visited.size() != n)   //直到遍历所有节点
    {
        int tmp = INT_MAX;
        int tmp1 = 0;
        for(auto i:visited)
            for (auto j : m1[i])
            {
                if (j[1] < tmp&&visited.find(j[0])== visited.end())
                {
                    tmp = j[1];
                    tmp1 = j[0];
                }
            }
        visited.insert(tmp1);
        dis += tmp; 
    }
}
int main()
{
    cin >> n >> m;
    int u,v,e;
    for (int i = 0; i < m; ++i)
    {
        cin >> u >> v >> e;
        m1[u].push_back({ v,e });
        m1[v].push_back({ u,e });
        q.insert(e);
    }
    dis = 0;
    visited.insert(1);
    dfs();
    cout << dis << endl;
}