leetcode 226. Invert Binary Tree

倒置二叉树

• 思路：分别倒置左边和右边的结点，然后把根结点的左右指针分别指向右左倒置后返回的根结点。

# 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 not root:

            return None

        left = self.invertTree(root.left)

        right = self.invertTree(root.right)

        root.left = right

        root.right = left

        return root