http://qs321.pair.com?node_id=607704


in reply to Re: Permuting with duplicates and no memory
in thread Permuting with duplicates and no memory

I borrowed this for something and noticed that if $num=8 this produces only 40319 permutations... I made the following el cheapo minor modification on mine.

sub make_orderings { my $num = shift; my @arr = (1 .. $num); my $first = 1; return sub { if( $first ) { $first = 0; return @arr; } my $last = $#arr; my $i = $last - 1; $i-- while 0 <= $i && $arr[$i] >= $arr[$i+1]; return if $i == -1; @arr[$i+1..$last] = reverse @arr[$i+1..$last] if $arr[$i+1] > $arr[$last]; my $j=$i+1; $j++ while $arr[$i] >= $arr[$j]; @arr[$i,$j] = @arr[$j,$i]; return @arr; } }

-Paul