Get the previous numeric tree in the ordered set of numeric trees with
the same node count as the given tree. If the tree is the 1st in its
ordered set, we decrement node count and return the last tree in this
ordered set. The process stops when node count reaches 3, after which
the given tree is returned unchanged.
Get the previous numeric tree in the ordered set of numeric trees with the same node count as the given tree. If the tree is the 1st in its ordered set, we decrement node count and return the last tree in this ordered set. The process stops when node count reaches 3, after which the given tree is returned unchanged.