AC_stack_n.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
# Author:      illuz <iilluzen[at]gmail.com>
# File:        AC_stack_n.py
# Create Date: 2015-07-26 10:53:38
# Usage:       AC_stack_n.py 
# Descripton:  


# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    # @param {TreeNode} root
    # @return {TreeNode}
    def invertTree(self, root):
        stack = [root]
        while stack:
            node = stack.pop()
            if node:
                node.left, node.right = node.right, node.left
                stack.append(node.left)
                stack.append(node.right)
                
        return root