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 }