226. Invert Binary Tree

Invert a binary tree.

Example:

Input:

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

Output:

     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 f*** off.

思路:递归 代码：python3

class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        if root:
            root.left,root.right = self.invertTree(root.right),self.invertTree(root.left)
            return root