prim

priority_queue<pair<int,int>,vector<pair<int,int> >,greater<pair<int,int> >q;
int prime() {
    ans = 0;
    q.push(make_pair(0, 1));
    while (q.size()) {
        int c = q.top().first, x = e[q.top().second].t;
        q.pop();
        if (!v[x]) {
            v[x] = 1;
            ans += c;
            add(e[i].f, e[i].t, e[i].w);
            add(e[i].t, e[i].f, e[i].w);
            for (int i = h[x]; i; i = e[i].n) {
                if (minc[e[i].t] > e[i].w && !v[e[i].t]) {
                    minc[e[i].t] = e[i].w;
                    q.push(make_pair(e[i].w, i));
                }
            }
        }
    }
}