Pseudo-code for shelf-stacking - php

Question

Suppose I have some serially numbered items that are 1-n units wide, that need to be displayed in rows. Each row is m units wide. I need some pseudo-code that will output the rows, for me, so that the m-width limit is kept. This is not a knapsack problem, as the items must remain in serial number order - empty spaces at the end of rows are fine.
I've been chasing my tail over this, partly because I need it in both PHP and jQuery/javascript, hence the request for pseudo-code....

Answer 1

while (!items.isEmpty()) {
rowRemain = m;
rowContents = [];
while (!items.isEmpty() && rowRemain > items[0].width) {
i = items.shift();
rowRemain -= i.width
rowContents.push(i);
}
rows.push(rowContents);
}
Running time is Θ(number of items)

Answer 2

Modulus is your friend. I would do something like:
$items = array(/* Your list of stuff */);
$count = 0;
$maxUnitsPerRow = 4; // Your "m" above
while ($item = $items[$count]) {
if ($count % $maxUnitsPerRow == 0) {
$row = new row();
}
$row->addItemToRow($item);
$count++;
}

Answer 3

Here is an alternative php code ...
function arrayMaxWidthString($items, $maxWidth) {
$out = array();
if (empty($items)) {
return $out;
}
$row = $maxWidth;
$i = 0;
$item = array_shift($items);
$row -= strlen($item);
$out[0] = $item;
foreach ($items as $item) {
$l = strlen($item);
$tmp = ($l + 1);
if ($row >= $tmp) {
$row -= $tmp;
$out[$i] = (($row !== $maxWidth) ? $out[$i] . ' ' : '') . $item;
} elseif ($row === $maxWidth) {
$out[$i] = $item;
++$i;
} else {
++$i;
$row = $maxWidth - $l;
$out[$i] = $item;
}
}
return $out;
}

Answer 4

For what it's worth, I think I have what I was looking for, for PHP - but not sure if there is a simpler way...
<?php
// working with just a simple array of widths...
$items = array(1,1,1,2,1,1,2,1);
$row_width = 0;
$max_width = 2;
echo "Begin\n"; // begin first row
foreach($items as $item=>$item_width) {
// can we add item_width to row without going over?
$row_width += $item_width;
if($row_width < $max_width) {
echo "$item_width ";
} else if($row_width == $max_width) {
echo "$item_width";
echo "\nEnd\nBegin\n"; // end last row, begin new row
$row_width = 0;
} else if($row_width == 2* $max_width) {
echo "\nEnd\nBegin\n"; // end last row, begin new row
echo "$item_width";
echo "\nEnd\n"; // end new row
$row_width = 0;
if($item < count($items)) echo "Begin\n"; // new row
} else if($row_width > $max_width) {
echo "\nEnd\nBegin\n"; // end last row, begin new row
echo "$item_width";
$row_width = $item_width;
}
}
echo "\nEnd\n"; // end last row
?>