#!/usr/bin/perl

use warnings; use strict; use Time::HiRes qw(gettimeofday tv_interval); 

my( @suit, @deck); my @ups = qw( 0 0 0 0 0 0 0 0 0 0); my $cntr = 0; 

Deck();	# four shuffled suits are added to a deck and then shuffled

print "\n"; my $t0 = gettimeofday;

T0:	$ups[0] = Card(); $ups[1] = Card(); # draw cards for pos #0 & #1
T1:	if($ups[0] eq $ups[1]) { goto T0; }	# cover a pair & go back

	if($ups[2] eq '0') { $ups[2] = Card(); } # fill pos#2 if vacant

	# check pos#2 against pos#0 - cover a pair & go back
	if($ups[2] eq $ups[0]) { Cover(2,0); goto T1; }
	# check pos#2 against pos#1 - cover a pair & go back
  	if($ups[2] eq $ups[1]) { Cover(2,1); goto T1; }

	# watch the rows for pairs that don't get covered
	foreach my $x (@ups) { print "$x "; } print "\n"; 

	for(my $j=3;$j<10;$j++) {
		if($ups[$j] eq '0') { $ups[$j] = Card(); }
		for(my $k=0;$k<$j;$k++) {
			if($ups[$j] eq $ups[$k]) { Cover($j,$k); goto T1; } } }	 

TX:	print "\n";
	foreach my $x (@ups) { print "$x "; } print "\t\tExit row\n"; 
	
	my $del_t = (gettimeofday - $t0) * 10**6;
	my $usec = sprintf("%.2f",$del_t);  
	print "\n$cntr passes in $usec microseconds. ";
	if($cntr == @deck) { print "Success!\n\n"; }
	else { print "{sigh...}\n\n"; }	

#========================================

sub Card {	my $tmp = $deck[$cntr]; $cntr++;
			if($tmp ne 'X') { return $tmp; } else { goto TX; } }

sub Suit {	@suit = qw(A B C D E F G H I J K L M ); 
			for(my $i=$#suit;$i>0;$i--) {
			my $j = int(rand($i + 1));
			@suit[$i, $j] = @suit[$j, $i]; } }	

sub Deck {	for(my $i=0;$i<4;$i++) { Suit(); @deck = (@deck,@suit); }
			for(my $i=$#deck;$i>0;$i--) {
				my $j = int(rand($i + 1));
				@deck[$i, $j] = @deck[$j, $i];
			} push(@deck,"X"); }

sub Cover { my $x = $_[0]; my $y = $_[1];
			$ups[$x] = Card(); $ups[$y] = Card(); }