int tree :: f1_1(tree_node *root, int k, int &res)
{
    tree_node *r;
    int count_child=0;
    if(!root)
        return 0;
    r = root->child;
    while(r)
    {
        count_child++;
        f1_1(r,k,res);
        r = r->brother;
    }
    if(count_child==k)
        res++;
    return 0;
}
int tree :: f1(tree_node *root, int k)
{
    int ret=0;
    f1_1(root,k,ret);
    return ret;
}