Re: Perl ARRAY() result

[stevieb]

There are a few responses to this post, but what I'd like to see, is a response with the full code body.

Can you do that guys?

I can run the code, even under strict/warnings, but I see sticky things, like the lack of the instantiation variable in the for loop for example. Typically, we don't use C-style for() loops in Perl code unless under duress, or weird circumstances. There are a couple of other smaller things, but I digress.

Anyone willing to post the full code that they have that got this to work, with the actual output from OPs example?

[kschwab]

Here's pme's changes as the whole script.

use strict;
use warnings;

sub Solve {
    my ( $goal, $elements ) = @_;
    my ( @results, $RecursiveSolve, $nextValue );
    $RecursiveSolve = sub {
        my ( $currentGoal, $included, $index ) = @_;
        for ( ; $index < @$elements ; ++$index ) {
            $nextValue = $elements->[$index];
            if ( $currentGoal > 2 * $nextValue ) {
                $RecursiveSolve->(
                    $currentGoal - $nextValue,
                    [ @$included, $nextValue ],
                    $index + 1
                );
            }
            else {
                if ( $currentGoal == $nextValue ) {
                    #print join( ',', @$included, $nextValue ), "\n";
                    push @results, [ @$included, $nextValue ];
                }
                return if $nextValue >= $currentGoal;
            }
        }
    };
    $RecursiveSolve->( $goal, [], 0 );
    undef $RecursiveSolve;    # Avoid memory leak from circular refere
+nce
    return @results;
}

my @results = Solve( 869,
    [ 15, 43, 51, 56, 60, 67, 122, 152, 193, 204, +229, 271, 293, 301 
+] );

foreach my $result (@results) {
    print join(',',@$result),"\n";
}

[stevieb]

Absolutely brilliant!

++ and kudos for denoting a circular reference :)

[kschwab]

Oh, I didn't do anything here other than merge pme's changes with the original post and fix the formatting a little.

[BillKSmith]

OK stevieb, here is the original OP code with only the print statement corrected as described in my first post. A sample execution demonstrates that the expected output is produced.

>type pviki.pl
use strict;
use warnings;
 sub Solve
{
  my ($goal, $elements) = @_;

  # For extra speed, you can remove this next line

  my (@results, $RecursiveSolve, $nextValue);

  $RecursiveSolve = sub {
    my ($currentGoal, $included, $index) = @_;

    for ( ; $index < @$elements; ++$index) {
      $nextValue = $elements->[$index];
      # Since elements are sorted, there's no point in trying a
      # non-final element unless it's less than goal/2:
      if ($currentGoal > 2 * $nextValue) {
        $RecursiveSolve->($currentGoal - $nextValue,
                          [ @$included, $nextValue ],
                          $index + 1);
      } else {
         #print "@$_\n", [ @$included, $nextValue ]
         local $, = q(, );
         print  @$included, $nextValue, "\n"
            if $currentGoal == $nextValue;
        return if $nextValue >= $currentGoal;
      }
    } # end for
  }; # end $RecursiveSolve

  $RecursiveSolve->($goal, [], 0);
  undef $RecursiveSolve; # Avoid memory leak from circular reference
  return @results;
} # end Solve


my @results = Solve(869, [15, 43, 51, 56, 60, 67, 122, 152, 193, 204,
+229, 271, 293, 301]
);


>perl pviki.pl
15, 43, 51, 56, 60, 122, 229, 293,
15, 43, 51, 56, 204, 229, 271,
15, 43, 51, 67, 193, 229, 271,
15, 43, 51, 122, 152, 193, 293,
15, 56, 60, 67, 122, 152, 193, 204,
15, 56, 60, 122, 152, 193, 271,
15, 56, 204, 293, 301,
15, 67, 193, 293, 301,
43, 51, 56, 67, 122, 229, 301,
43, 51, 56, 67, 152, 229, 271,
43, 51, 60, 193, 229, 293,
43, 122, 204, 229, 271,
56, 60, 67, 122, 271, 293,
56, 67, 152, 293, 301,