Splitting the WordPress loop for alternate grids

alternative.php

<div class="grid">
<?php
	posts_from_loop( 2, function() {
		get_template_part( 'partials/post-w50' );
	});
?>
</div>

<div class="grid">
<?php
	posts_from_loop( 3, function() {
		get_template_part( 'partials/post-w33' );
	});
?>
</div>

<?php while ( have_posts() ) { 
	the_post(); 
	?>
	<?php get_template_part( 'partials/post-w100' ); ?>
<?php } ?>

solution.php

<?php
/**
 * Fetch a specific amount of posts from the main query.
 *
 * @param integer  $amount Amount of posts.
 * @param callback $callback A callback function.
 * @return void
 */
function posts_from_loop( $amount, $callback ) {
	global $wp_query;

	while ( ( $count < $amount ) && ( $wp_query->current_post + 1 < $wp_query->post_count ) ) {
		$wp_query->the_post();

		$callback();

		$count++;
	}
}

usual.php

<?php

$count = 0;

while ( have_posts() ) {

	the_post();

	if ( $count == 0 || $count == 2 ) {
		echo '<div class="grid">';
	}

	if ( $count <= 1 ) {
		get_template_part( 'partials/post-w50' );
	} elseif ( $count > 1 && $count <= 4 ) {
		get_template_part( 'partials/post-w33' );
	} else {
		get_template_part( 'partials/post-w100' );
	}

	if ( $count == 1 || $count == 4 ) {
		echo '</div>';
	}

	$count++;
}

Example of the grid: