(Easy) Invert Binary Tree

 

Given the root of a binary tree, invert the tree, and return its root.

 

Input: root = [4,2,7,1,3,6,9] 

Output: [4,7,2,9,6,3,1]

 

Example 2:

Input: root = [2,1,3] Output: [2,3,1]

 

Example 3:

Input: root = [] 

Output: []

 

풀이

class Solution:

def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:

 

if not root:

return None

 

left = self.invertTree(root.left)

right = self.invertTree(root.right)

root.left = right
root.right = left

return root