Split total into 5 different numbers - php

Question

Ok what i'm wanting to do is split a number ($row['count']) into 5, this is easy enough if you want equal numbers:
$sum = ($row['count'] / 5);
$fsum = floor($sum);
but I want each number to be different and still add up to total ie $row['count'] how can this be achieved?
Update:
If this helps its to be used to update 5 rows in a database:
$query = "SELECT * FROM foo";
$result = mysql_query($query);
while ($row = mysql_fetch_array($result)) {
$sum = ($row['count'] / 5);
$fsum = floor($sum);
$id = $row['id'];
$update = "UPDATE foo SET foo1='$fsum', foo2='$fsum', foo3='$fsum', foo4='$fsum', foo5='$fsum' WHERE id='$id'";
mysql_query($update);
}// while
so ideally the $update query would be something like:
$update = "UPDATE foo SET foo1='$fsum1', foo2='$fsum2', foo3='$fsum3', foo4='$fsum4', foo5='$fsum5' WHERE id='$id'";

Answer 1

This is my take:
function randomize($sum, $parts) {
$part_no = count($parts);
$continnue_counter = 0;
while (count(array_unique($parts)) != $part_no) {
$changing = array_rand($parts, 2);
if (($parts[$changing[0]] - 1) == 0 || ($parts[$changing[1]] - 1) == 0) { // don't let them go under 1
++$continnue_counter;
// sometime one element get everything and others even out on 1
// just throw away everything you got so far and start over
if ($continnue_counter > 10) {
$parts = setup($sum, $part_no);
$continnue_counter = 0;
}
continue;
}
$continnue_counter = 0;
$signum = mt_rand(0, 100) % 2 ? 1 : -1;
$delta = $signum * mt_rand(1, min($parts[$changing[0]] - 1, $parts[$changing[1]] - 1)); // -1 to make sure they don't go under 0
$parts[$changing[0]] += $delta;
$parts[$changing[1]] -= $delta;
}
return $parts;
}
function setup($sum, $part_no) {
$parts = array_fill(0, $part_no, (int)($sum / $part_no));
// acount for the reminder of (int) cast
$reminder = $sum - array_sum($parts);
while ($reminder) {
$parts[array_rand($parts)] += 1;
--$reminder;
}
return $parts;
}
$part_no = 5;
$sum = 42;
$parts = randomize($sum, setup($sum, $part_no));
var_export($parts);
print array_sum($parts)
Update:
I've added a version that introduces a little more entropy.
Update2:
The more random one had a tendency to decrement everything to 1 except one part, added an explicit detection to deal with this. Still the algorithm behind it has unknown termination time.