def isSymmetric(self, root: TreeNode) -> bool: def recur(L, R): if not L and not R: return True if not L or not R or L.val != R.val: return False return recur(L.left, R.right) and recur(L.right, R.left) return recur(root.left, root.right) if root else True
原文：https://www.cnblogs.com/fuj905/p/12902148.html