【剑指offer】对称的二叉树

题目描述

请实现一个函数，用来判断一颗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
        
        def ismirror(left,right):
            
            if left == None and right == None:
                return True
            elif left == None or right == None:
                return False
                
            if left.val != right.val:
                return False
            
            ret1=ismirror(left.left,right.right)
            ret2=ismirror(left.right,right.left)
            
            return ret1 and ret2
        if pRoot == None:
            return True
        return ismirror(pRoot.left,pRoot.right)