.say for combinations(5,3);
(0 1 2)
(0 1 3)
(0 1 4)
(0 2 3)
(0 2 4)
(0 3 4)
(1 2 3)
(1 2 4)
(1 3 4)
(2 3 4)
sub combinations(Int $n, Int $k) {
return ([],) unless $k;
return if $k > $n || $n <= 0;
my @c = ^$k;
gather loop {
take [@c];
next if @c[$k-1]++ < $n-1;
my $i = $k-2;
$i-- while $i >= 0 && @c[$i] >= $n-($k-$i);
last if $i < 0;
@c[$i]++;
while ++$i < $k { @c[$i] = @c[$i-1] + 1; }
}
}
.say for combinations(5,3);