Brute force solution. I wanted to have it near the top (along with my random solution) to show how an inefficient, but obvious solution would work. I would hope that solutions down the line would have much better performance and more creativity. :-)

Note: I have seen someone (cannot remember who) calling Knuth's algorithm for mastermind a brute force algorithm. If it is the one I am thinking of, it is not a brute force algorithm, but (1) trims impossible solutions, and (2) orders guesses by highest potential of helping do (1) on the next pass.

sub MidLifeXis_bruteforce {
  my $p     = shift;
  my $v     = shift;
  my $check = shift;

  my $worker = sub {
    my $worker   = shift;
    my $prefix   = shift;
    my $tot_size = shift;
    my $places   = shift;
    my $alphabet = shift;
    my $check    = shift;

    my @solution = ( 0, 0 );
    foreach my $letter (@$alphabet) {
      if ($places < 1) {
    return '';
      }
      elsif ($places == 1) {
    @solution = $check->( $prefix . $letter );
    return ( $prefix . $letter ) if ( $solution[1] == $tot_size );
      }
      else {
    my $try = $worker->( $worker,
                 $prefix . $letter,
                 $tot_size,
                 $places - 1,
                 [ grep { $_ ne $letter } @$alphabet ],
                 $check,
               );
    return $try if $try;
      }
    }
    return '';
  };

  $worker->( $worker,
         '',
         $p,
         $p,
         [ ( '0' .. '9', 'A' .. 'Z' )[ 0 .. $v - 1 ] ],
         $check,
       );
}

[download]

--MidLifeXis

Please consider supporting my wife as she walks in the 2009 Alzheimer's Walk.

In reply to Re^2: Challenge: Optimal Bagels Strategy (Solutions) by MidLifeXis
in thread Challenge: Optimal Bagels Strategy by Limbic~Region

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