How to make 5 random numbers with sum of 100

Question

do you know a way to split an integer into say... 5 groups. Each group total must be at random but the total of them must equal a fixed number.

for example I have \"

Answer 1

This should do what you need:

<?php
$tot = 100;
$groups = 5;
$numbers = array();
for($i = 1; $i < $groups; $i++) {
    $num = rand(1, $tot-($groups-$i));
    $tot -= $num;
    $numbers[] = $num;
}
$numbers[] = $tot;

It won't give you a truly balanced distribution, though, since the first numbers will on average be larger.

Answer 2

Depending on how random you need it to be and how resource rich is the environment you plan to run the script, you might try the following approach.

<?php
set_time_limit(10);

$number_of_groups   = 5;
$sum_to             = 100;

$groups             = array();
$group              = 0;

while(array_sum($groups) != $sum_to)
{
    $groups[$group] = mt_rand(0, $sum_to/mt_rand(1,5));

    if(++$group == $number_of_groups)
    {
        $group  = 0;
    }
}

The example of generated result, will look something like this. Pretty random.

[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(11)
  [1]=>
  int(2)
  [2]=>
  int(13)
  [3]=>
  int(9)
  [4]=>
  int(65)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(9)
  [1]=>
  int(29)
  [2]=>
  int(21)
  [3]=>
  int(27)
  [4]=>
  int(14)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(18)
  [1]=>
  int(26)
  [2]=>
  int(2)
  [3]=>
  int(5)
  [4]=>
  int(49)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(20)
  [1]=>
  int(25)
  [2]=>
  int(27)
  [3]=>
  int(26)
  [4]=>
  int(2)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(9)
  [1]=>
  int(18)
  [2]=>
  int(56)
  [3]=>
  int(12)
  [4]=>
  int(5)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(0)
  [1]=>
  int(50)
  [2]=>
  int(25)
  [3]=>
  int(17)
  [4]=>
  int(8)
}
[root@server ~]# php /var/www/dev/test.php
array(5) {
  [0]=>
  int(17)
  [1]=>
  int(43)
  [2]=>
  int(20)
  [3]=>
  int(3)
  [4]=>
  int(17)
}