题目描述
- 递归遍历+交换
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def mirrorTree(self, root: TreeNode) -> TreeNode:
if not root:
return root
# 左右子树都存在，则交换，再继续遍历
if root.left and root.right:
root.left, root.right = root.right, root.left
root.left = self.mirrorTree(root.left)
root.right = self.mirrorTree(root.right)
# 只有左或右子树存在，将其镜像翻转
elif root.left:
root.left, root.right = None, self.mirrorTree(root.left)
elif root.right:
root.left, root.right = self.mirrorTree(root.right), None
return root
官方写法更简洁
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def mirrorTree(self, root: TreeNode) -> TreeNode:
if not root:
return root
left = self.mirrorTree(root.left)
right = self.mirrorTree(root.right)
root.left, root.right = right, left
return root
