python--leetcode226. Invert Binary Tree

Invert a binary tree.

4
/   \
2     7
/ \   / \
1   3 6   9

to

4
/   \
7     2
/ \   / \
9   6 3   1

Trivia:
This problem was inspired by this
original tweet by Max
Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.
题目意思就是给你一个二叉树，让你去反转它，把左右子树反转。

解题思路：递归解决。

# 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:
def invert(root):
temp=root.left
root.left=root.right
root.right=temp
if root.left:
invert(root.left)
if root.right:
invert(root.right)
invert(root)
return root

更快捷解法：

def invertTree(self, root):
if root:
root.left, root.right = self.invertTree(root.right), self.invertTree(root.left)
return root