lixoo_verteces

vector<int> adj[MAXV];
int dfs_num[MAXV], dfs_low[MAXV],  dfs_parent[MAXV], vertex[MAXV];
int dfscounter, V, cont, dfsRoot, rootChildren;

void artvertex(int u) {

    dfs_low[u] = dfs_num[u] = dfscounter++;
    int tam = adj[u].size();
    rep(j,0,tam){
         int v = adj[u][j];
         if (dfs_num[v] == -1) {
            dfs_parent[v] = u;
            if (u == dfsRoot)
                rootChildren++;
            artvertex(v);
            if (dfs_low[v] >= dfs_num[u])
                 vertex[u] = true;
            dfs_low[u] = min(dfs_low[u], dfs_low[v]);
         }
         else if (v != dfs_parent[u])
              dfs_low[u] = min(dfs_low[u], dfs_num[v]);
    }
}

int main(){

    rep(i,0,V+1){
            dfs_low[i] = dfs_parent[i] = vertex[i] = 0;
            dfs_num[i] = -1;
        }

        rep(i,0,V)
            if (dfs_num[i] == -1) {
                 dfsRoot = i; rootChildren = 0;
                 artvertex(i);
                 vertex[dfsRoot] = (rootChildren > 1);
            }
    int ans = 0;
    rep(i,0,V)
        if (vertex[i])
        ans++;
    printf("%d",ans);
}