<?php
// Returns the total number of $count-length strings generatable from $letters.
function getPermCount($letters, $count)
{
$result = 1;
// k characters from a set of n has n!/(n-k)! possible combinations
for($i = strlen($letters) - $count + 1; $i <= strlen($letters); $i++) {
$result *= $i;
}
return $result;
}
// Decodes $index to a $count-length string from $letters, no repeat chars.
function getPerm($letters, $count, $index)
{
$result = '';
for($i = 0; $i < $count; $i++)
{
$pos = $index % strlen($letters);
$result .= ",".$letters[$pos];
$index = ($index-$pos)/strlen($letters);
$letters = substr($letters, 0, $pos) . substr($letters, $pos+1);
}
return trim($result, ",");
}
$letters = 'abc';
$r = array();
//echo '1 letters from 4: ';
for($i = 0; $i < getPermCount($letters, 1); $i++)
$r[] = getPerm($letters, 1, $i);
//echo '2 letters from 4: ';
for($i = 0; $i < getPermCount($letters, 2); $i++)
$r[] = getPerm($letters, 2, $i);
//echo ' 3 letters from 4: ';
for($i = 0; $i < getPermCount($letters, 3); $i++)
$r[] = getPerm($letters, 3, $i);
print_r($r);
- Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
- Array
(
[0] => a
[1] => b
[2] => c
[3] => a,b
[4] => b,a
[5] => c,a
[6] => a,c
[7] => b,c
[8] => c,b
[9] => a,b,c
[10] => b,a,c
[11] => c,a,b
[12] => a,c,b
[13] => b,c,a
[14] => c,b,a
)
preferences:
243.1 ms | 406 KiB | 350 Q