Symmetric tree

leetcode

# 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 True

        def dfs(left,right):
            if not left and not right: return True
            if not left or not right : return False
            if left.val!= right.val: return False
            return dfs(left.left,right.right) and dfs(left.right,right.left)
        return dfs(root.left,root.right)