Witam,

znalazłem na stronie:
http://php.net/manual/en/function.shuffle.php w komentarzach kod

[PHP] pobierz, plaintext 
 
<?php
 
/*
 Use: $arr = power_perms($in);
 
 Example:
  $in = array("A","B","C");
  $power_perms = power_perms($in);
 
 Returns:
  Array
  (
    [0] => Array
        (
            [0] => A
            [1] => B
            [2] => C
        )
 
    [1] => Array
        (
            [0] => A
            [1] => C
            [2] => B
        )
 
    [2] => Array
        (
            [0] => B
            [1] => A
            [2] => C
        )
 
    [3] => Array
        (
            [0] => B
            [1] => C
            [2] => A
        )
 
    [4] => Array
        (
            [0] => C
            [1] => A
            [2] => B
        )
 
    [5] => Array
        (
            [0] => C
            [1] => B
            [2] => A
        )
 
    [6] => Array
        (
            [0] => A
            [1] => B
        )
 
    [7] => Array
        (
            [0] => B
            [1] => A
        )
 
    [8] => Array
        (
            [0] => B
            [1] => C
        )
 
    [9] => Array
        (
            [0] => C
            [1] => B
        )
 
    [10] => Array
        (
            [0] => A
            [1] => C
        )
 
    [11] => Array
        (
            [0] => C
            [1] => A
        )
 
    [12] => Array
        (
            [0] => A
        )
 
    [13] => Array
        (
            [0] => B
        )
 
    [14] => Array
        (
            [0] => C
        )
 
  )
 
*/
 
function power_perms($arr) {
 
    $power_set = power_set($arr);
    $result = array();
    foreach($power_set as $set) {
        $perms = perms($set);
        $result = array_merge($result,$perms);
    }
    return $result;
}
 
function power_set($in,$minLength = 1) {
 
   $count = count($in);
   $members = pow(2,$count);
   $return = array();
   for ($i = 0; $i < $members; $i++) {
      $b = sprintf("%0".$count."b",$i);
      $out = array();
      for ($j = 0; $j < $count; $j++) {
         if ($b{$j} == '1') $out[] = $in[$j];
      }
      if (count($out) >= $minLength) {
         $return[] = $out;
      }
   }
 
   //usort($return,"cmp");  //can sort here by length
   return $return;
}
 
function factorial($int){
   if($int < 2) {
       return 1;
   }
 
   for($f = 2; $int-1 > 1; $f *= $int--);
 
   return $f;
}
 
function perm($arr, $nth = null) {
 
    if ($nth === null) {
        return perms($arr);
    }
 
    $result = array();
    $length = count($arr);
 
    while ($length--) {
        $f = factorial($length);
        $p = floor($nth / $f);
        $result[] = $arr[$p];
        array_delete_by_key($arr, $p);
        $nth -= $p * $f;
    }
 
    $result = array_merge($result,$arr);
    return $result;
}
 
function perms($arr) {
    $p = array();
    for ($i=0; $i < factorial(count($arr)); $i++) {
        $p[] = perm($arr, $i);
    }
    return $p;
}
 
function array_delete_by_key(&$array, $delete_key, $use_old_keys = FALSE) {
 
    unset($array[$delete_key]);
 
    if(!$use_old_keys) {
        $array = array_values($array);
    }
 
    return TRUE;
}
?>
 
[PHP] pobierz, plaintext 

lecz otrzymany wynik algorytmu nie zgadza się z przykładem podanym przez autora:

pod odkomentowaniu linii: usort($return,"cmp"); i dodaniu funkcji cmp:

[PHP] pobierz, plaintext 
function cmp($a, $b)
{
	if ($a == $b) {
		return 0;
	}
	return ($a > $b) ? -1 : 1;
}
[PHP] pobierz, plaintext 

wyniki nie są podane w identycznej kolejności tylko:

[PHP] pobierz, plaintext 
Array
(
    [0] => Array
        (
            [0] => A
            [1] => B
            [2] => C
        )
 
    [1] => Array
        (
            [0] => A
            [1] => C
            [2] => B
        )
 
    [2] => Array
        (
            [0] => B
            [1] => A
            [2] => C
        )
 
    [3] => Array
        (
            [0] => B
            [1] => C
            [2] => A
        )
 
    [4] => Array
        (
            [0] => C
            [1] => A
            [2] => B
        )
 
    [5] => Array
        (
            [0] => C
            [1] => B
            [2] => A
        )
 
    [6] => Array
        (
            [0] => B
            [1] => C
        )
 
    [7] => Array
        (
            [0] => C
            [1] => B
        )
 
    [8] => Array
        (
            [0] => A
            [1] => C
        )
 
    [9] => Array
        (
            [0] => C
            [1] => A
        )
 
    [10] => Array
        (
            [0] => A
            [1] => B
        )
 
    [11] => Array
        (
            [0] => B
            [1] => A
        )
 
    [12] => Array
        (
            [0] => C
        )
 
    [13] => Array
        (
            [0] => B
        )
 
    [14] => Array
        (
            [0] => A
        )
)
[PHP] pobierz, plaintext 

macie może pomysł dlaczego?