#!/usr/bin/perl

#program will generate all unique combinations of 4 from a pool of players
#without repeating any pair of players

use strict;
use  Math::Combinatorics;

my $count;
my %seen;

sub trackSeen{
	my @players = @{$_[0]};
	#For each set of 4 players the following positions are ones we do not want to see again
	my @pairs = ($players[0].$players[1], #0,1 
				$players[0].$players[2], #0,2 
				$players[0].$players[3], #0,3 
				$players[1].$players[2], #1,2 
				$players[1].$players[3], #1,3 
				$players[2].$players[3]  #2,3
	); 
	foreach my $pair (@pairs){
		$seen{$pair} = 1;
	}
}

sub notSeen{
	my @players = @{$_[0]};
	my @pairs = ($players[0].$players[1], #0,1 
				$players[0].$players[2], #0,2 
				$players[0].$players[3], #0,3 
				$players[1].$players[2], #1,2 
				$players[1].$players[3], #1,3 
				$players[2].$players[3]  #2,3
	);
	foreach my $pair (@pairs){
		if (scalar grep /$pair/, keys(%seen) ){
			return 0;
		}
	}
	return 1;
}

my @n = 'A'..'X';
my $comboObj = Math::Combinatorics->new(count => 4, data => [@n]);
print "combinations of 4 from: " . join(" ", @n)."\n";
print "-----------------------------" . ("----" x scalar(@n))."\n";
while ( my @combo = $comboObj->next_combination){
	if ( notSeen(\@combo)  == 1) {
		print join(', ', @combo) . "\n";
		$count++;
		trackSeen(\@combo);
	} 
}

print "$count combinations\n";