[LeetCode]题解（python）：101-Symmetric Tree

题目来源：

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

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题意分析：

　　判断一棵树是不是镜像树。

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题目思路：

　　判断左子树的左右子树是不是和右子树的右左子树相同。

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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 solve(p,q):
            if p == None:
                return q == None
            if q == None:
                return p == None
            if p.val == q.val:
                return solve(p.left,q.right) and solve(p.right,q.left)
            return False
        if root == None:
            return True
        else:
            return solve(root.left,root.right)