return 1;
}
if ($n === $r) {
return fac($n);
}
if ($n <= $r) {
die('Total number of items must be greater than number of items taken' . PHP_EOL);
}
return fac($n) / fac($n - $r);
}
function nCk($n, $k)
{
if ($n === 0) {
die('Total number of items cannot be 0.');
}
if ($n < $k) {
die('Number of items taken cannot be greater than total number of items.');
}
if ($k == 0) {
return $n;
}
return fac($n) / (fac($n - $k) * fac($k));
}
for ($i = 1; $i < $argc; ++$i) {
echo "{$argv[$i]}! = " . fac($argv[$i]) . PHP_EOL;
if ($i % 2 === 0) {
$j = $i - 1;
echo "There are " . nPr($argv[$j], $argv[$i]) . " Permutations for {$argv[$i]} from {$argv[$j]}" . PHP_EOL;
echo "There are " . nCk($argv[$j], $argv[$i]) . " Combinations for {$argv[$i]} from {$argv[$j]}" . PHP_EOL;
}
}
function nPr($n, $r)
{
if ($r > $n) {
return NaN;
}
if ($r) {
return $n * nPr($n - 1, $r - 1);
} else {
return 1;
}
}
