Fixing Permute Output - php

Question

Hey there I've made a recursive permutation function for class, but I output is less than favorable.
http://codepad.org/DOaMP9oc
function permute($arr) {
$out = array();
if (count($arr) > 1) {
$i = 0;
foreach($arr as $r => $c) {
$n = $arr;
unset($n[$r]);
$out[$c] = permute($n);
}
}
else
return array_shift($arr);
return $out;
}
If input is array(1,2,3,4,5), Output is:
Array
(
[1] => Array
(
[2] => Array
(
[3] => Array
(
[4] => 5
[5] => 4
)
[4] => Array
(
[3] => 5
[5] => 3
)
[5] => Array
(
[3] => 4
[4] => 3
)
)
ETC......................
This is all Correct, you can read it like this key.key.key.key.value or 12345,12354,12435
Currently, to convert this output to something readable, I'm using this ugly block of code:
http://codepad.org/qyWcRBCl
foreach($out as $k => $a)
foreach($a as $l => $b)
foreach ($b as $m => $c)
foreach ($c as $n => $d)
echo $k.$l.$m.$n.$d.'<br>';
How can I alter my function to eliminate the foreach stack and output in a similar format from permute().

Answer 1

My solution is to work on strings:
function permute($string) {
if (strlen($string)<2) {
return array($string);
}
$permutations = array();
// Copy everything but the first character of the string.
$copy = substr($string, 1);
foreach (permute($copy) as $permutation) {
$length = strlen($permutation);
// Insert the first character of the original string.
for ($i=0; $i<=$length; $i++) {
$permutations[] = substr($permutation, 0, $i) . $string[0] . substr($permutation, $i);
}
}
sort($permutations);
return $permutations;
}
header('Content-type:text/plain');
print_r(permute('12345'));
You already have a working implementation so I have no qualms in giving that to you. Note that the array is not created in order, so I simply sort it at the end. Also note that this only works on things that you intend to have the value of 1 character, so doing a permutation of car names would not work.
Even if you don't like this answer, I suggest that you use a type-hint for array:
function permute(array $arr) {
This will enforce that you pass an array into it.

Answer 2

function display_permutation($array){
if(is_array($array)){
foreach($array as $key => $val){
echo $key;
display_permutation($val);
}
}else{
echo $array;
}
}

Answer 3

Here is my permutation function and we can display results in simple way
class Permute {
public $results = Array();
public function __construct(array $array) {
$this->_permute($array);
}
private function _permute(array $orig, array $perm = Array()) {
if(!count($orig)) {
$this->results[] = $perm;
return null;
}
$count = count($orig);
for($i = 0; $i < $count; ++$i) {
$orig2 = $orig;
unset($orig2[$i]);
$orig2 = array_values($orig2);
$perm2 = $perm;
$perm2[] = $orig[$i];
$this->_permute($orig2, $perm2);
}
}
}
$arr = Array(1,2,3,4,5);
$permute = new Permute($arr);
foreach($permute->results as $result) {
echo join('', $result).'<br>';
}

Answer 4

I opted to use the following function:
function showPerms($a,$i='') {
if (is_array($a))
foreach($a as $k => $v)
showPerms($v,$i.$k);
else
echo $i.$a."\n";
}
However, I'd still like to do this in a singular recursive function.