# -*- 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

        return self.isSymBT(pRoot, pRoot)

    def isSymBT(self, tree1, tree2):

        if tree1 == None and tree2 == None:

            return True

        if tree1 == None or tree2 == None:

            return False

        if tree1.val != tree2.val:

            return False

        return self.isSymBT(tree1.left, tree2.right) and self.isSymBT(tree1.right, tree2.left)