Python3解leetcode Symmetric Tree

问题描述：

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

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

But the following [1,2,2,null,3,null,3] is not:

Note:
Bonus points if you could solve it both recursively and iteratively.

思路：二分类树的问题，可以考虑递归解法

# Definition for a binary tree node.

# class TreeNode:

#     def __init__(self, x):

#         self.val = x

#         self.left = None

#         self.right = None

class Solution:

    def isSymmetric(self, root: TreeNode) -> bool:

        if root == None:

            return True

        def ismirror(root1,root2):

            if root1 == None and root2 ==None:

                return True

            elif root1 == None or root2 ==None or root1.val != root2.val:

                return False

            return ismirror(root1.left,root2.right) and ismirror(root1.right,root2.left) 

        return ismirror(root.left,root.right)

巴特西

Python3解leetcode Symmetric Tree

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