Leetcode103:二叉树的锯齿形层序遍历

# 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: TreeNode) -> List[List[int]]:
        res = []
        if not root:
            return res
        queue = [root]
        while len(queue):
            inner = []
            for i in range(len(queue)):
                node = queue.pop()
                inner.append(node.val)
                if node.left:
                    queue.insert(0,node.left)
                if node.right:
                    queue.insert(0,node.right)
            res.append(inner.copy())
        for i in range(len(res)):
            if i%2:
                res[i].reverse()
        return res