Hi L~R, 
  1 use List::AllUtils qw/sum/;
  2 use Bit::Vector;
  3 
  4 my $k = 2;
  5 
  6 my @letters = split '',"ABCDE";
  7 my $n = scalar(@letters);
  8 
  9 my $vec = Bit::Vector->new($n);
 10 
 11 while(!$vec->increment){
 12     my $i = $vec->to_Bin; # current bitstring
 13     my $s = sum(split '',$i); # sum up to find out how many bits a
+re lit
 14 
 15     next unless ($s == $k); # just the ones with $k bits lit
 16 
 17 
 18     my $str = # convert bitstring to string
 19         join '',
 20         map { $letters[$_]  }
 21         grep { $vec->contains($_);  }
 22         0..$n-1 ;
 23 
 24     print "$s $i $str\n";
 25 };

[download]

The seen and set_seen routines are incorporated in the check at line 15.

The output for this is:

2 00011 AB
2 00101 AC
2 00110 BC
2 01001 AD
2 01010 BD
2 01100 CD
2 10001 AE
2 10010 BE
2 10100 CE
2 11000 DE

[download]

In reply to Re^3: Algorithm to convert combinations to bitstring by spx2
in thread Algorithm to convert combinations to bitstring by Limbic~Region

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