[leetcode] 226. Invert Binary Tree @ python-优快云博客

本文链接：https://blog.youkuaiyun.com/danspace1/article/details/87701567

本文详细介绍了如何使用递归和深度优先搜索(DFS)两种方法实现二叉树的翻转，通过代码示例清晰地展示了算法的具体实现过程。

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原题

Invert a binary tree.

Example:

Input:

/
2 7
/ \ /
1 3 6 9
Output:

/
7 2
/ \ /
9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so f*** off.

解法1

递归

代码

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def invertTree(self, root: 'TreeNode') -> 'TreeNode':
        if not root:
            return
        
        root.left, root.right = self.invertTree(root.right), self.invertTree(root.left)
        return root

解法2

DFS

代码

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def invertTree(self, root: 'TreeNode') -> 'TreeNode':
        q = [root]
        while q:
            node = q.pop()
            if node:
                node.left, node.right = node.right, node.left
                q.extend([node.left, node.right])
        return root