Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level).
Given binary tree
3 / \ 9 20 / \ 15 7
return its level order traversal as:
[ , [9,20], [15,7] ]
Also think about a version of the question where you are asked to do a level order traversal of the tree when depth of the tree is much greater than number of nodes on a level.