problem address
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.思路很简单，先根遍历的翻版，主要是找到节点将左右子树对调即可
# Definition for a binary tree node. # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: def invertTree(self, root: TreeNode) -> TreeNode: if root: root.left, root.right = root.right, root.left self.invertTree(root.left) self.invertTree(root.right) return root