题目描述

blablabla

样例

blablabla

算法1

() $O(n^2)$

blablabla

时间复杂度分析：blablabla

Python 代码

# 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 isSymmetric(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        return not root or self.dfs(root.left, root.right)
    def dfs(self, p, q):
        if not q or not p:
            return not p and not q
        return p.val == q.val and self.dfs(q.left, p.right) and self.dfs(q.right, p.left)