给你二叉树的根节点 root ，返回其节点值的 锯齿形层序遍历 。（即先从左往右，再从右往左进行下一层遍历，以此类推，层与层之间交替进行）。

解题思路

python列表可以很简单用reverse，remove的方法来实现双向队列，所以很简单

AC代码

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:if not root:return []queue = [root]flag = Trueres = []while queue:templist = []if flag:length = len(queue)for _ in range(length):temp = queue[0]templist.append(temp.val)if temp.left: queue.append(temp.left)if temp.right: queue.append(temp.right)queue.remove(temp)flag = not flagelse:length = len(queue)for i in range(length - 1, -1, -1):temp = queue[i]templist.append(temp.val)if temp.right: queue.append(temp.right)   if temp.left: queue.append(temp.left)queue.remove(temp)queue.reverse()flag = not flagres.append(templist)return res