PHP : Combinations without permutations - php

Question

This code gives me every possible combination of n values with a length of x, to have a sum of n.
function GETall_distri_pres($n_valeurs, $x_entrees, $combi_presences = array()) {
if ($n_valeurs == 1) {
$combi_presences[] = $x_entrees;
return array($combi_presences);
}
$combinaisons = array();
// $tiroir est le nombre de chaussettes dans le tiroir suivant
for ($tiroir = 0; $tiroir <= $x_entrees; $tiroir++) {
$combinaisons = array_merge($combinaisons, GETall_distri_pres(
$n_valeurs - 1,
$x_entrees - $tiroir,
array_merge($combi_presences, array($tiroir))));
}
return $combinaisons;
}
I need to generate only unique distributions for example not having [2,1,1,0] and [1,2,1,0], only [2,1,1,0].
var_dump(GETall_distri_pres(3,3)) will give :
array (size=10)
0 =>
array (size=3)
0 => int 0
1 => int 0
2 => int 3
1 =>
array (size=3)
0 => int 0
1 => int 1
2 => int 2
2 =>
array (size=3)
0 => int 0
1 => int 2
2 => int 1
3 =>
array (size=3)
0 => int 0
1 => int 3
2 => int 0
4 =>
array (size=3)
0 => int 1
1 => int 0
2 => int 2
5 =>
array (size=3)
0 => int 1
1 => int 1
2 => int 1
6 =>
array (size=3)
0 => int 1
1 => int 2
2 => int 0
7 =>
array (size=3)
0 => int 2
1 => int 0
2 => int 1
8 =>
array (size=3)
0 => int 2
1 => int 1
2 => int 0
9 =>
array (size=3)
0 => int 3
1 => int 0
2 => int 0
Do you have any ideas?

Answer 1

This would be an approach: before returning the computed set you filter them by creating a fresh associative array, using the normalized permutations as keys. That will result in permutations overwriting themselves, so that only one will get preserved:
<?php
function GETall_distri_pres($n_valeurs, $x_entrees, $combi_presences = array()) {
if ($n_valeurs == 1) {
$combi_presences[] = $x_entrees;
return array($combi_presences);
}
$combinaisons = array();
// $tiroir est le nombre de chaussettes dans le tiroir suivant
for ($tiroir = 0; $tiroir <= $x_entrees; $tiroir++) {
$combinaisons = array_merge($combinaisons, GETall_distri_pres(
$n_valeurs - 1,
$x_entrees - $tiroir,
array_merge($combi_presences, array($tiroir))));
}
// filter out permutations
$filteredCombinations = [];
array_walk($combinaisons, function($entry) use(&$filteredCombinations) {
arsort($entry);
$filteredCombinations[join('', $entry)] = $entry;
});
return array_values($filteredCombinations);
}
$result = GETall_distri_pres(3, 3);
print_r($result);
The output obviously is:
Array
(
[0] => Array
(
[0] => 3
[1] => 0
[2] => 0
)
[1] => Array
(
[0] => 2
[1] => 1
[2] => 0
)
[2] => Array
(
[0] => 1
[1] => 1
[2] => 1
)
)