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).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ \
9 20
/ \
15 7
return its zigzag level order traversal as:
[
[3],
[20,9],
[15,7]
]
广度优先遍历，用一个bool记录是从左到右还是从右到左，每一层结束就翻转一下。
{% codesnippet "./code/binary-tree-zigzag-level-order-traversal-1."+book.suffix, language=book.suffix %}{% endcodesnippet %}
{% codesnippet "./code/binary-tree-zigzag-level-order-traversal-2."+book.suffix, language=book.suffix %}{% endcodesnippet %}