请实现一个函数,用来判断一棵二叉树是不是对称的。注意,如果一个二叉树同此二叉树的镜像是同样的,定义其为对称的。
# -*- coding:utf-8 -*- # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: def isSymmetrical(self, pRoot): # write code here if not pRoot: return True return self.isS(pRoot.left, pRoot.right) def isS(self, p1, p2): if not p1 and not p2: return True if not p1 or not p2: return False return p1.val == p2.val and self.isS(p1.left, p2.right) and self.isS(p1.right, p2.left)