LeetCode:226. Invert Binary Tree

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原创最新推荐文章于 2026-07-06 08:18:01 发布 201 阅读 AI 写同款· GEO 优化 ›

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Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9
Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

翻转二叉树

思路：递归翻转左右子树

Python 代码实现

# 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(root == None):
            return None
        if(root.left == None and root.right == None):
            return root
        else:
            tmp = root.right
            root.right = root.left
            root.left = tmp
            
            if (root.left != None):
                self.invertTree(root.left)
            if (root.right != None):
                self.invertTree(root.right)
            return root

注意下停止条件：节点为空或者左右子节点都为空的情况。

思路二：迭代

根据上面的递归的方法，改写成迭代的形式：

Python 代码实现

class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        queue = []
        if (root != None):
            queue.append(root)
            while(len(queue) > 0):
                t = queue.pop(0)
                leftTmp = t.left
                t.left = t.right
                t.right = leftTmp
                if (t.left != None):
                    queue.append(t.left)
                if (t.right != None):
                    queue.append(t.right)
            
        return root