# 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 check(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 check(left.left, right.right) and check(left.right, right.left) return check(root.left,root.right)