[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