Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).
Given binary tree [3,9,20,null,null,15,7],
return its zigzag level order traversal as:
Given a binary tree, it is required to output z-type sequence traversal.
Solution: for hierarchical traversal, we can think of using queue to...