leetcode 101.对称二叉树（不会做）

遇到递归就抓瞎

# 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 isSymmetric(self, root: Optional[TreeNode]) -> bool:
        if not root:
            return root
        
        return self.check(root.left,root.right)
    
    def check(self,left_node: Optional[TreeNode],right_node: Optional[TreeNode]):

        if left_node == None and right_node == None:
            return True
        
        if left_node==None or right_node==None:
            return False

        if left_node.val != right_node.val:
            return False
        
        outside = self.check(left_node.left,right_node.right)
        inside = self.check(left_node.right,right_node.left)

        return outside and inside