原题：
https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/
思路，如果无从下手，先要了解二叉树的广度优先遍历 BSF :
https://www.cnblogs.com/Jomini/p/12032020.html
参考答案:
https://blog.csdn.net/qq_39313597/article/details/89669927
Leetcode103_Binary-tree-zigzag-level-order-traversal
原文：https://www.cnblogs.com/Jomini/p/12032378.html