LeetCode226：Invert Binary Tree

Invert a binary tree.

Example:

Input:

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

Output:

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

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LeetCode：链接

和剑指Offer_编程题18：二叉树的镜像是一样的。

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