backup

    for (int j = 0; u_node != NULL; j = (j + 1) % 26)
    {
        if (u_node -> children == NULL)
        {
            // free node
            if (u_node != NULL)
            {
                free(u_node);
            }

            return true;
        }
        else
        {
            if (u_node -> children[j] != NULL)
            {
                // recursively call self
                unload_helper(u_node -> children[j]);
            }
        }
    }