Re: Perl Card Trick

[Flexx]

Hi again,

BTW, nice post, Lysander, I really got hung on that one...

Below is my quickshot version. Of course, a serious version of this would need input checks, etc., etc. I was just courious how I'd do this in a generalized way, using a flat array (like a talon of cards). This version allows for matrices of arbitrary dimensions.

The print_matrix sub should therefore also be generic for all (quadratic) arrays -- where sqrt(@array) returns a natural number (an integer).

#!/usr/bin/perl

use strict;

my $dimension = shift || 4;

my @card_matrix = (1 .. $dimension ** 2);

print_matrix(@card_matrix);
print "\nrow? : "; my $row = <STDIN>; chomp($row);

print_matrix(reverse @card_matrix);
print "\ncol? : "; my $col = <STDIN>; chomp($col);

print "\nsolution: ", 
    $card_matrix[($row - 1) * $dimension + ($dimension - $col)];


sub print_matrix
{
  my @matrix = @_;
    
  my $dimension = sqrt(@matrix);
    
  printf "\n" . "\t[%d]" x $dimension, (1..$dimension);
        
    for(my $row = 0; $row < $dimension; $row++)
    {
      printf "\n[%d]" . "\t%d" x $dimension, 
             $row + 1, @matrix[$row * $dimension .. $row * $dimension 
++ $dimension - 1];
    }
}

So long,
Flexx