leetcode系列（11）二叉树翻转 Invert Binary Tree

Invert a binary tree

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

to

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

整个题目有意思的是Homebrew作者的google白板编程跪事件，所以这个题目的后面也说了：

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

用递归可以方便解决，invert根节点的左子树和子树，然后交换两个子树木，就是invert了整个树

C++代码

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    TreeNode* invertTree(TreeNode* root) {        if (root != NULL) {            TreeNode* tmp = root->left;            root->left = invertTree(root->right);            root->right = invertTree(tmp);        }        return root;    }};

Python代码

# Definition for a binary tree node.# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution:    # @param {TreeNode} root    # @return {TreeNode}    def invertTree(self, root):        if root != None:            tmp = root.left            root.left = self.invertTree(root.right)            root.right = self.invertTree(tmp)        return root