[LeetCode]Invert Binary Tree

Invert Binary Tree

Invert a binary tree.

     4
   /   
  2     7
 /    / 
1   3 6   9

     4
   /   
  7     2
 /    / 
9   6 3   1

我觉得返回void更好一些，就地翻转。

还是递归实现方便。

 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 *temp = root->left;
15         root->left = invertTree(root->right);
16         root->right = invertTree(temp);
17         return root;
18     }
19 };