Invert Binary Tree

 1     public TreeNode invertTree(TreeNode root) 
 2     {
 3         TreeNode newroot = root;
 4         if(root==null)return newroot;
 5         helper(root,newroot);
 6         return newroot;
 7         
 8     }
 9     
10     public TreeNode helper(TreeNode root,TreeNode newroot)
11     {
12         if(root==null) return newroot;
13         TreeNode temp = root.left;
14         root.left=root.right;
15         root.right=temp;
16         helper(root.left,newroot);
17         helper(root.right,newroot);
18         return newroot;
19         
20     }