[LeetCode] Invert Binary Tree

Invert Binary Tree

Invert a binary tree.

     4

   /   \

  2     7

 / \   / \

1   3 6   9

to

     4

   /   \

  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 fuck off.

 

额， 这也不能怪Google，既然你这么吊，连这道题都做不出来就真的太不应该了。

(╯°□°)╯︵ ǝǝɹʇ ʎɹɐuıq

 1 /**

 2  * Definition for a binary tree node.

 3  * struct TreeNode {

 4  *     int val;

 5  *     TreeNode *left;

 6  *     TreeNode *right;

 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 8  * };

 9  */

10 class Solution {

11 public:

12     TreeNode* invertTree(TreeNode* root) {

13         if (root == NULL) return NULL;

14         TreeNode *res = new TreeNode(root->val);

15         res->left = invertTree(root->right);

16         res->right = invertTree(root->left);

17         return res;

18     }

19 };