tree        : perfectly balanced BST on 1..15
nodes n     : 15,  height h = 3
right spine : 8 -> 12 -> 14 -> 15

maxBST          -> 15   nodes visited: 4
maxBSTIterative -> 15   nodes visited: 4
maxByFullScan   -> 15   nodes visited: 15  (forbidden)
minBST          -> 1   nodes visited: 4

left-leaning chain 10,9,...,1 (h = 9)
  maxBST -> 10   nodes visited: 1
  minBST -> 1   nodes visited: 10

empty tree  : max() of an empty tree is undefined
