Count ACF Repeater Rows, add closing syntax to even/odd

<?php

    $d=1; if( have_rows('testimonials') ): while ( have_rows('testimonials') ) : the_row();

    $rows = get_field('testimonials');
    $row_count = count($rows);

    if($d==1) echo '<div class="col-sm-6"><ul class="tstLst">';
?>

        <li>
            <?php the_sub_field('testimonial_content'); ?>
            <b class="author">- <?php the_sub_field('testimonial_author'); ?></b>
        </li>

    <?php if($d==2) echo '</ul></div>'; ?>

<?php if($d==2) $d=1; else $d++; endwhile; if( $row_count & 1 ) echo '</ul></div>'; endif; ?>