(59).按之字形顺序打印二叉树

题目描述

请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。
说明：本题目包含复杂数据结构TreeNode，点此查看相关信息

# -*- 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
        if not pRoot:
            return []
        ret = []
        curr_stack = [pRoot]
        while curr_stack:
            next_stack = []
            curr_vals = []
            for node in curr_stack:
                if node.left:
                    next_stack.append(node.left)
                if node.right:
                    next_stack.append(node.right)
                curr_vals.append(node.val)
            curr_stack = next_stack
            ret.append(curr_vals)
        result = []
        for i,v in enumerate(ret):
            if i%2==0:
                result.append(v)
            else:
                result.append(v[::-1])
        return result