PHP permutation multiple same elements

Question

I need a function which returns all possible combinations,

e.g.

chars = range('a', 'c');

= a a a
= a a b
= a b a
= a b b
= a b c
= a c b ... n. = c c c

(order doesn't matter)

and so on

i got this

function pc_permute($items, $perms = array( )) {
    if (empty($items)) {
        $return = array($perms);
    }  else {
        $return = array();
        for ($i = count($items) - 1; $i >= 0; --$i) {
             $newitems = $items;
             $newperms = $perms;
         list($foo) = array_splice($newitems, $i, 1);
             array_unshift($newperms, $foo);
             $return = array_merge($return, pc_permute($newitems, $newperms));
         }
    }
    return $return;
}

$p = pc_permute(array(0, 1, 2, 3));
var_dump($p);

from Here

But i wasn't able to figure out how to chance/rewrite this to get all possible combination with multiple same elements.

Thanks, Mohammer

Vipin Jain · Accepted Answer · 2012-11-09 08:12:01Z

1

Please use this function:

<?php 
$characters = range('a','c');


function get_permutations(array $arr = array()){
    if(count($arr) == 1){
        return array_values($arr);
    }

    $return_array = array();

    foreach($arr as $key => $val){
        $temp_arr = $arr;
        unset($temp_arr[$key]);
        $temp = call_user_func(__FUNCTION__, $temp_arr);
        for($x = 0; $x < count($temp); $x++){
            $temp[$x] = $val.$temp[$x];
        }
        $return_array = array_merge($return_array, $temp);
    }
    return $return_array;
}

var_dump(get_permutations($characters));

Output:

array(6) {
  [0]=>
  string(3) "abc"
  [1]=>
  string(3) "acb"
  [2]=>
  string(3) "bac"
  [3]=>
  string(3) "bca"
  [4]=>
  string(3) "cab"
  [5]=>
  string(3) "cba"
}

EDIT:

<?php 
$characters = range('a','h');


function get_permutations(array $arr = array(), $max_length = NULL){
    if(count($arr) == 1 || ($max_length !== NULL && $max_length <= 1)){
        return array_values($arr);
    }

    $return_array = array();

    foreach($arr as $key => $val){
        $temp_arr = $arr;
        unset($temp_arr[$key]);
        $temp = call_user_func(__FUNCTION__, $temp_arr, $max_length !== NULL ? $max_length - 1 : NULL);
        for($x = 0; $x < count($temp); $x++){
            $temp[$x] = $val.$temp[$x];
        }
        $return_array = array_merge($return_array, $temp);
    }
    return $return_array;
}

var_dump(get_permutations($characters, 4));

NOTE: Beware using a-z range will lead to a greater runtime or even leads to out of memory error so i tested it with a small range :)

edited Nov 9, 2012 at 8:12

answered Nov 6, 2012 at 12:48

Vipin Jain

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2 Comments

Mohammer Over a year ago

Thanks, works aboslutly perfect!! How could I modify this function to get range('a','z'); but with a predefined string-length, e.g. 5chars?

Vipin Jain Over a year ago

@Mohammer : sorry for l8 response, pass another variable and set the value and test the value to be zero and on each recursion decrease the value, check the edits in some time

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