Custom rewrite URL for CPT

add_filter( 'post_type_link', '_custom_link' , 10, 2 );
function _custom_link( $post_link, $id = 0 ) {
    $post = get_post($id);
    if ( is_wp_error($post) || 'company' != $post->post_type || empty($post->post_name) )
        return $post_link;
    return home_url(user_trailingslashit( "$post->post_name" ));
}
add_action('init', '_custom_rewrite_rule');
function _custom_rewrite_rule() {
    add_rewrite_rule('(.*?)$', 'index.php?company=$matches[1]', 'top');
}