劍指offer 二叉樹的鏡像（二叉樹的所有子節點互換）

題目描述

操作給定的二叉樹，將其變換爲源二叉樹的鏡像。

輸入描述:

二叉樹的鏡像定義：源二叉樹 
    	    8
    	   /  \
    	  6   10
    	 / \  / \
    	5  7 9 11
    	鏡像二叉樹
    	    8
    	   /  \
    	  10   6
    	 / \  / \
    	11 9 7  5

解法一：遞歸

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回鏡像樹的根節點
    def Mirror(self, root):
        # write code here
        if root == None:
            return 
        root.left, root.right = root.right, root.left
        if root.left:
            self.Mirror(root.left)
        if root.right:
            self.Mirror(root.right)

解法二：非遞歸

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回鏡像樹的根節點
    def Mirror(self, root):
        # write code here
        if root == None:
            return 


        stackNode = []
        stackNode.append(root)
        while len(stackNode) > 0:
            nodeNum = len(stackNode) - 1
            tree = stackNode[nodeNum]
            stackNode.pop()
            nodeNum -= 1
            if tree.left != None or tree.right != None:
                tree.left, tree.right = tree.right, tree.left
            if tree.left:
                stackNode.append(tree.left)
                nodeNum += 1
            if tree.right:
                stackNode.append(tree.right)
                nodeNum += 1