class Solution {
    public static void reverse(TreeNode node)
    {
        TreeNode temp=node.left;
        node.left=node.right;
        node.right=temp;
        if(node.right!=null)
            reverse(node.right);
        if(node.left!=null)
            reverse(node.left);
    }

    public void mirror(TreeNode root) {
        if(root==null)
            return;
        reverse(root);
    }
}