101. 对称二叉树

1. 题目链接

2. 解题思路：递归的思路，就是左子树和右子树的值相等，同时，左子树的左子树与右子树的右子树要相似，左子树的右子树与右子树的左子树要相似。看代码很清晰

3. 代码

   class Solution:
   
       def process(self, node1, node2) -> bool:
           if node1 == None and node2 == None:
               return True
           if node1 == None:
               return False
           if node2 == None:
               return False
           return node1.val == node2.val and self.process(node1.left, node2.right) and self.process(node1.right, node2.left)
       def isSymmetric(self, root: Optional[TreeNode]) -> bool:
           return self.process(root.left, root.right)