<?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 $result;
}
$letters = 'abcd';
echo '2 letters from 4: ';
for($i = 0; $i < getPermCount($letters, 2); $i++)
echo getPerm($letters, 2, $i).' ';
echo ' 3 letters from 4: ';
$r = array();
for($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 - 5.6.38, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
- 2 letters from 4: ab ba ca da ac bc cb db ad bd cd dc 3 letters from 4: Array
(
[0] => abc
[1] => bac
[2] => cab
[3] => dab
[4] => acb
[5] => bca
[6] => cba
[7] => dba
[8] => adb
[9] => bda
[10] => cda
[11] => dca
[12] => abd
[13] => bad
[14] => cad
[15] => dac
[16] => acd
[17] => bcd
[18] => cbd
[19] => dbc
[20] => adc
[21] => bdc
[22] => cdb
[23] => dcb
)
preferences:
227.26 ms | 406 KiB | 452 Q