LeeCode-Invert Binary Tree

Invert a binary tree.

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

to

     4
   /   \
  7     2
 / \   / \
9 6 3 1
 
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode invertTree(TreeNode root) {
        
        
        if(root!=null)  
        {
        TreeNode temp  = root.left;  
        root.left = root.right;  
        root.right = temp;  
          
        invertTree(root.left);  
        invertTree(root.right);  
          
        return root;   
        }
        return null;
    }
}