gistfile1.txt

#!/usr/bin/env perl6

my int $checks = 0;
my int $limit = 100_000;

my @numbers = 3 .. 11 ;
my @array ;

recurse_magic_box( @numbers, @array ) ;

sub recurse_magic_box ( @numbers , @array ) {
    my $set = set(@array);
    for @numbers -> int $n {
        unless $set{$n} {
            @array.push($n);
            if @array < 9 or check_magic_box( @array ) {
                recurse_magic_box( @numbers, @array ) ;
                }
            @array.pop ;
            }
        }
    }

=for optimizations
    this little piece should be at least as fast as the recursion strategy,
    but isn't. it's Probably just .permutations that wants to get the "GLR"
    treatment.

#for (flat 3..11).permutations -> $array {
    #check_magic_box($array);
    #}

sub check_magic_box ( @array ) {
    #return 0 if @array > 9 ;
    #return 0 if (set @array) != @array;
    #say "check $checks magic box for @array[]";
    exit if $checks++ == $limit;
    #if ( @array.elems == 9 ) {
        # say @array ;
        my $sum = 21 ;
        return 0 if $sum != @array[0] + @array[1] + @array[2] ;
        return 0 if $sum != @array[3] + @array[4] + @array[5] ;
        return 0 if $sum != @array[6] + @array[7] + @array[8] ;
        return 0 if $sum != @array[0] + @array[3] + @array[6] ;
        return 0 if $sum != @array[1] + @array[4] + @array[7] ;
        return 0 if $sum != @array[2] + @array[5] + @array[8] ;
        return 0 if $sum != @array[0] + @array[4] + @array[8] ;
        return 0 if $sum != @array[6] + @array[4] + @array[2] ;
        say @array[ 0 .. 2 ] ;
        say @array[ 3 .. 5 ] ;
        say @array[ 6 .. 8 ] ;
        say '' ;
        #}
    1;
    }


# real	104m3.203s
# user	93m25.498s
# sys	0m10.577s

# I think I'm doing something wrong, because this shouldn't take that long, but I don't know what.