题解 | #按之字形顺序打印二叉树#

参考了评论区大佬思路：
1.通过while语句遍历树
2.使用enumerate 实现之字形打印

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def Print(self, pRoot):
        # write code here
        ##首先判断是否存在根节点
        if not pRoot:
            return []
        nodestack = [pRoot]
        result = []
        while nodestack:
            res = []
            nextstack = []
            for i in nodestack:
                res.append(i.val)
                if i.left:
                    nextstack.append(i.left)
                if i.right:
                    nextstack.append(i.right)
            nodestack = nextstack
            result.append(res)
        returnRes = []
        for idx,v in enumerate(result):
            if idx%2==0:
                returnRes.append(v)
            else:
                returnRes.append(v[::-1])
        return returnRes