Deleting

We want to delete a node i.

• If i has zero child, delete it.
• If i has one child, delete i and move i's child into i's place.
• If i has two children, let j be the successor of i. Delete j in place (it has at most one child, so that's easy). Now, move j into i's place.

Why is this well defined? In particular, how do we know that j has at most one child?