When joining nodes, set parent pointers of the left and right children of the upper node (if they exist) to point to the new node.
When joining nodes, set parent pointers of the left and right children of
the upper node (if they exist) to point to the new node.

each/bind9-collab,each/bind9-collab,pecharmin/bind9,each/bind9-collab,pecharmin/bind9,pecharmin/bind9,pecharmin/bind9,pecharmin/bind9,each/bind9-collab,each/bind9-collab,pecharmin/bind9,each/bind9-collab