CODEWITHSUNDEEP
php
Claudio Delgado
Claudio Delgado

Reputation: 2349

Divide a single number into a set of unique random numbers in PHP

I want to start with a predetermined single number, but then have multiple random numbers that when added up, their total is the number I started with.

For example, I have 100, but want to have 10 random numbers that when they are added together, make up 100.

With my limited knowledge, I wrote this:

<?php
$_GET['total'] = $total;
$_GET['divided'] = $divided;
echo 'Starting with total: ' . $total;
echo '<br />';
echo 'Divided between: ' . $divided;
$randone = rand(1, $total);
$randonecon = $total - $randone;
echo '<br />';
echo 'First random number: ' . $randone;
$randtwo = rand(1, $randonecon);
$randtwocon = $total - $randtwo;
echo '<br />';
echo 'Second random number: ' . $randtwo;
?>

Of course, it's a failure, because I don't know how to make the numbers be in an array that doesn't let them exceed the given total.

Thanks entirely to Matei Mihai, it's done! 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Randomize</title>
</head>

<body>

<?php

$_GET['total'] = $total;
$_GET['divided'] = $divided;


function generateRandomNumbers($max, $count)
{
$numbers = array();

    for ($i = 1; $i < $count; $i++) {
        $random = mt_rand(0, $max / ($count - $i));
        $numbers[] = $random;
        $max -= $random;
    }

    $numbers[] = $max;

    return $numbers;
}
echo '<pre>'; 
print_r(generateRandomNumbers($total, $divided));
echo '</pre>';

?>


<form id="form1" name="form1" method="get" action="">
  <label for="total">Total</label>
  <br />
  <input type="text" name="total" id="total" />
  <br /> 
   <label for="divided">Divided</label>
  <br />
  <input type="text" name="divided" id="divided" />
  <br />
  <input type="submit" value="Go!">
</form>
</body>
</html>

Upvotes: 3

Views: 1982

Answers (1)

Mihai Matei
Mihai Matei

Reputation: 24276

You can try using a small function to generate these numbers:

function generateRandomNumbers($max, $count)
{
    $numbers = [];

    for ($i = 1; $i < $count; $i++) {
        $random = mt_rand(0, $max / ($count - $i));
        $numbers[] = $random;
        $max -= $random;
    }

    $numbers[] = $max;

    shuffle($numbers);

    return $numbers;
}

echo '<pre>';
print_r(generateRandomNumbers(100, 10));
echo '</pre>';

The function will generate an array like:

Array
(
    [0] => 0
    [1] => 1
    [2] => 6
    [3] => 11
    [4] => 14
    [5] => 13
    [6] => 3
    [7] => 6
    [8] => 13
    [9] => 33
)

Please note that instead of $random = mt_rand(0, $max / ($count - $i)); I could use directly $random = mt_rand(0, $max) but in the later case the chances to get a lot of 0 in the resulted array are bigger than the first case.

Upvotes: 6

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