catwang01#Algorithm#Leetcode 226. 翻转二叉树1

[toc] # Leetcode 226. 翻转二叉树 ## 问题描述 [226. 翻转二叉树 - 力扣（LeetCode）](https://leetcode-cn.com/problems/invert-binary-tree/) ## 算法 只需要遍历每个结点，交换其左右结点即可。使用 preorder、inorder、postorder、levelorder均可 ### 解法1: preorder dfs #### 解法1: 实现：递归 ##### 解法1: 实现:python ``` class Solution: def invertTree(self, root: TreeNode) -> TreeNode: def process(node): if not node: return node.left, node.right = node.right, node.left def preorder(node, process): if not node: return process(node) preorder(node.right, process) preorder(node.left, process) preorder(root, process) return root ``` #### 解法1: 实现2: 非递归 ##### 解法1: 实现2: python ``` class Solution: def invertTree(self, root: TreeNode) -> TreeNode: node = root stack = [] while stack or node: while node: # preorder processing node.left, node.right = node.right, node.left stack.ap