leetcode之Invert Binary Tree

这个题目就是反转左右节点。很简单啊。代码如下：

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

class Solution(object):
def invertTree(self, root):
"""
:type root: TreeNode
:rtype: TreeNode
"""
if root == None:
return None
if root.left != None:
if root.right != None:
root.left, root.right = root.right, root.left
self.invertTree(root.left)
self.invertTree(root.right)
else:
root.right = root.left
root.left = None
self.invertTree(root.right)
else:
if root.right != None:
root.left = root.right
root.right = None
self.invertTree(root.left)
return root