# 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 is None: return None if root.left: self.invertTree(root.left) if root.right: self.invertTree(root.right) root.left,root.right=root.right,root.left return root