题目描述：
方法一：递归
class Solution: def mirrorTree(self, root: TreeNode) -> TreeNode: if not root:return root.left,root.right = self.mirrorTree(root.right),self.mirrorTree(root.left) return root
方法二：栈
class Solution: def mirrorTree(self, root: TreeNode) -> TreeNode: if not root:return stack = [root] while stack: node = stack.pop() if node.left:stack.append(node.left) if node.right:stack.append(node.right) node.left,node.right = node.right,node.left return root