0) {
echo join(" ", $arr);
} else {
echo "(empty)";
}
echo '
';
}
function print_power_sets($arr) {
echo "POWER SET of [" . join(", ", $arr) . "]
";
foreach (power_set($arr) as $subset) {
print_array($subset);
}
}
function power_set($arr) {
$binary = array();
foreach (range(1, count($arr)) as $i) {
$binary[] = false;
}
$n = count($arr);
$powerset = array();
while (count($binary) <= count($arr)) {
$powerset[] = get_subset($binary, $arr);
$i = 0;
while (true) {
if ($binary[$i]) {
$binary[$i] = false;
$i += 1;
} else {
$binary[$i] = true;
break;
}
}
$binary[$i] = true;
}
return $powerset;
}
print_power_sets(array());
print_power_sets(array('singleton'));
print_power_sets(array('dog', 'c', 'b', 'a'));
?>