[LeetCode]题解（python）：101 Symmetric tree

题目来源

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https://leetcode.com/problems/symmetric-tree/

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

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题意分析

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Input:一个二叉树

Output:True or False

Conditions: 判断一个二叉树是不是对称的

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题目思路

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一一对应判断值是否相等，注意要清楚谁对应谁。

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AC代码（Python）

 # 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
         """
         def help(p, q):
             if p == None and q == None:
                 return True
             if p and q and p.val == q.val:
                 return help(p.left, q.right) and help(p.right, q.left)
             return False

         if root:
             return help(root.left, root.right)
         return True