How to organize in chunks a not accurate division? - php

Question

I have a number of participants and a number of groups, and I have to organize the participants into groups.
Example:
10/3 = 3, 3 and 4.
10/9 = 2,2,2 and 4.
23/3 = 6,6,6 and 5.
I have tried with array_chunk using the size paramether as a rounded result of participants/groups but it Did not work well.
Edit with my problem solved.
$groups = $this->request->data['phases_limit'];
$classified_lmt = $this->request->data['classified_limit'];
$participants = count($game->user_has_game);
$participants_lmt = floor($participants / $groups);
$remainders = $participants % $groups;
if ($groups > $participants) {
throw new \Exception("Há mais grupos que participantes");
}
for ($i=0; $i < $groups; $i++) {
$p = $this->Phase->newEntity();
$p->name = 'Grupo #' . $game->id;
$p->game_id = $game->id;
$p->classified_limit = $classified_lmt;
$this->Phase->save($p);
// add the number of participants per group
for ($j=0; $j < $participants_lmt; $j++) {
$user_has_game = array_pop($game->user_has_game);
$g = $this->Phase->GroupUserHasGame->newEntity();
$g->group_id = $p->id;
$g->user_has_game_id = $user_has_game->id;
$this->Phase->GroupUserHasGame->save($g);
}
// check if it is the last iteration
if (($groups - 1) == $i) {
// add the remainders on the last iteration
for ($k=0; $k < $remainders; $k++) {
$user_has_game = array_pop($game->user_has_game);
$g = $this->Phase->GroupUserHasGame->newEntity();
$g->group_id = $p->id;
$g->user_has_game_id = $user_has_game->id;
$this->Phase->GroupUserHasGame->save($g);
}
}
}

Answer 1

Have you tried the modulus operator? It gives you the remainder after dividing the numerator by the denominator.
For example, if you want to split 10 people into 3 groups:
floor(10 / 3) = 3; // people per group
10 % 3 = 1; // 1 person left over to add to an existing group.
Edit - I included the following function as part of my original answer. This doesn't work for OP, however I want to leave it here, as it may help others.
function group($total, $groups)
{
// Calculate participants per group and remainder
$group = floor($total / $groups);
$remainder = $total % $groups;
// Prepare groupings and append remaining participant to first group
$groupings = array_fill(0, $groups, $group);
$groupings[0] += $remainder;
return $groupings;
}

Answer 2

Not sure there are off-the-shelf libraries for that. I just implemented something similar in Java if you need some ideas:
public List<Integer> createDistribution(int population_size, int groups) {
List<Integer> lst = new LinkedList();
int total = 0;
for (double d : createDistribution(groups)) {
// this makes smaller groups first int i = new Double(population_size * d).intValue();
int i = (int)Math.round(population_size * d);
total += i;
lst.add(i);
}
// Fix rounding errors
while (total < population_size) {
int i = r.nextInt(groups);
lst.set(i, lst.get(i) + 1);
total += 1;
}
while (total > population_size) {
int i = r.nextInt(groups);
if (lst.get(i) > 0) {
lst.set(i, lst.get(i) - 1);
total -= 1;
}
}
return lst;
}