LeeCode-Invert Binary Tree

Invert a binary tree.

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

to

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

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public TreeNode invertTree(TreeNode root) {
12         
13         
14         if(root!=null)  
15         {
16         TreeNode temp  = root.left;  
17         root.left = root.right;  
18         root.right = temp;  
19           
20         invertTree(root.left);  
21         invertTree(root.right);  
22           
23         return root;   
24         }
25         return null;
26     }
27 }