<?php
function factorial($n){
return array_product(range(1,$n));
}
function A($n,$m){
return factorial($n)/factorial($n-$m);
}
function C($n,$m){
return A($n,$m)/factorial($m);
}
function arrangement($a, $m) {
$r = array();
$n = count($a);
if ($m <= 0 || $m > $n) {
return $r;
}
for ($i=0; $i<$n; $i++) {
$b = $a;
$t = array_splice($b, $i, 1);
if ($m == 1) {
$r[] = $t;
} else {
$c = arrangement($b, $m-1);
foreach ($c as $v) {
$r[] = array_merge($t, $v);
}
}
}
return $r;
}
function combination($a, $m) {
$r = array();
$n = count($a);
if ($m <= 0 || $m > $n) {
return $r;
}
for ($i=0; $i<$n; $i++) {
$t = array($a[$i]);
if ($m == 1) {
$r[] = $t;
} else {
$b = array_slice($a, $i+1);
$c = combination($b, $m-1);
foreach ($c as $v) {
$r[] = array_merge($t, $v);
}
}
}
return $r;
}
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