101. 对称二叉树

题目描述

解题思路

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def f(self,a,b):
        if a == None and b != None:
            return False
        elif a == None and b == None:
            return True
        elif a != None and b == None:
            return False
        else:
            if a.val != b.val:
                return False
            else:
                res1 = self.f(a.left, b.right)
                res2 = self.f(a.right, b.left)
                return res1 and res2
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        if root == None:
            return True
        else:
            return self.f(root.left, root.right)

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