题解 | #对称的二叉树#

对称二叉树的本质首先搞清楚，分三种情况
1.在第二层：pRoot.left = pRoot.right
2.在第三层开始，root1.left == root2.right， root1.right == root2.left






# -*- 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 dfs(root1, root2):
            if not root1 and not root2:
                return True
            if not root1 or not root2:
                return False
            if root1.val == root2.val and dfs(root1.left, root2.right) and dfs(root1.right, root2.left):
                return True
            else:
                return False
        if not pRoot: return True
        return dfs(pRoot.left, pRoot.right)