A Binary Search Tree (BST) is recursively defined as a binary tree which
has the following properties:
The left subtree of a node contains only nodes with keys less than the
node's key.
The right subtree of a node contains only nodes with keys greater than
or equal to the node's key.
Both the left and right subtrees must also be binary search trees.
A Complete Binary Tree (CBT) is a tree that is completely filled, with
the possible exception of the bottom level, which is filled from left to right.
Now given a sequence of distinct non-negative integer keys, a unique
BST can be constructed if it is required that the tree must also be a
CBT. You are supposed to output the level order traversal sequence of
this BST.