#!/usr/bin/perl

use warnings;

sub third {

#this returns the the same number if the inputs
#are the same, or if they are different it returns the
#number that was not input (of the set {1,2,3})

	my @numbers = @_;
	if ( $numbers[0] == $numbers[1] ) {
		return $numbers[0];
	}
	else {
		if ( ($numbers[0] + $numbers[1]) == 3 ) {
			return 3;
		}
		elsif ( ( $numbers[0] + $numbers[1]) == 4 ) {
			return 2;
		}
		else {
			return 1;
		}
	}
}

sub find_match {

#this returns the match of two cards in an array of the form
#(a,b,c,d) of which a,b,c,d are each a number 1-3 to
#represent shape, color, pattern, and number of shapes
#on a card

	my @cards = @_;
	my @return;
	$return[0] = third($cards[0]->[0],$cards[1]->[0]);
        $return[1] = third($cards[0]->[1],$cards[1]->[1]);
        $return[2] = third($cards[0]->[2],$cards[1]->[2]);
        $return[3] = third($cards[0]->[3],$cards[1]->[3]);
	return @return;
}
sub combo { 

#this i stole from a perlmonks question to
#find every combination of 2 cards in a group

    my $by = shift;
    return sub { () } if ! $by || $by =~ /\D/ || @_ < $by;
    my @list = @_;

    my @position = (0 .. $by - 2, $by - 2);
    my @stop     = @list - $by .. $#list;
    my $end_pos  = $#position;
    my $done     = undef;

    return sub {
        return () if $done;
        my $cur = $end_pos;
        {
            if ( ++$position[ $cur ] > $stop[ $cur ] ) {
                $position[ --$cur ]++;
                redo if $position[ $cur ] > $stop[ $cur ];
                my $new_pos = $position[ $cur ];
                @position[ $cur .. $end_pos ] = $new_pos .. $new_pos + $by;
            }
        }
        $done = 1 if $position[0] == $stop[0];
        return @list[ @position ];
    }
}

#example cards

@card1=(2,2,1,1);
@card2=(2,2,3,3);
@card3=(2,2,2,2);
@card4=(2,2,3,2);

#example group of cards

@cards=(\@card1, \@card2, \@card3, \@card4);

#$iter finds a subset of length 2 of @cards

my $iter = combo( 2, @cards);

#this loop loops through every combo of two cards
#and looks for a potential match
#then checks to see if the match exists in the group of
#@cards
#the problem occurs because each match is found thrice

while ( my @combo = $iter->() ) {
	my @match = find_match(@combo);
	my $first = $combo[0];
	my $second = $combo[1];
	my @altered_cards = @cards;
	foreach $card (@cards) {
		if(join("",@match)==join("",@$card)){
			print "Match =", @match, "\n";
			print "Card =", @$card, "\n";
			print "Match!\n";
			 @$first, "\n", @$second, "\n", @match, "\n";
			last;
		}
	}
}