#!/usr/bin/perl

use strict;
use warnings;
my $Z;
my @array;
foreach (1..36){
    $Z->{1 + int rand(8)}++;
}

foreach (sort { $Z->{$a} <=> $Z->{$b}} keys %{$Z}){
    my $element = $_;
    foreach (1..$Z->{$element}){
    push @array, $element;
    }
}


@array = qw(2 8 8 8 1 1 1 1 5 5 5 5 7 7 7 7 4 4 4 4 4 4 3 3 3 3 3 3 3 
+6 6 6 6 6 6 6);

print join " " => @array,"\n";

sub get_pairs1 {
    print "====================\n";
    my @array = @_;
    my $X;
    my $hash;
    my $A;
    my $counter;
    my @pairs;
    foreach (@array){
    $X->{$_} += 1;
    }
    foreach my $x (sort { $a <=> $b } keys %{$X}){
    foreach my $y (sort { $a <=> $b } keys %{$X}){
        next if  $X->{$x} == 0;
        next if $x eq $y;
        next if $X->{$y} == 0;
        next if defined $hash->{$x}{$y};
        $counter++;
        print "$counter = $x $y\n";
        push @pairs, [$x,$y];
        $hash->{$x}{$y} = $hash->{$y}{$x} = 1;
        $X->{$x} -= 1;        $X->{$y} -= 1;
    }
    }
    print "$counter counts$/";
    return @pairs;
} 



sub get_pairs2 {
  my %hash = ();
  $hash{$_}++ foreach @_;
  my @keys = sort { $hash{$b} <=> $hash{$a} } keys %hash;
  my $counter = 0;
  my @pairs = ();
  
  foreach my $x (0..$#keys - 1) {
    next unless $hash{$keys[$x]};
    foreach my $y ($x+1..$#keys) {
      last unless $hash{$keys[$x]};
      next unless $hash{$keys[$y]};
      push @pairs, ($keys[$x] < $keys[$y] ? [$keys[$x],$keys[$y]]:[$ke
+ys[$y],$keys[$x]]);
      print scalar @pairs," = @{$pairs[$#pairs]}$/";
      $hash{$keys[$x]}--;
      $hash{$keys[$y]}--;
    }
  }
  print scalar @pairs," counts$/";
  return @pairs;
}

# assumes that all pairs within the array are unique
sub maximize_rows {
  my @array = @_;
  my $counter = 0;
  foreach my $x (0..$#array - 1) {
    foreach my $y ($x+1..$#array) {
      my %hash = ();
      $hash{$_}++ foreach (@{$array[$x]},@{$array[$y]});
      if (scalar keys %hash == 4) {
        $counter++;
        print "$counter = $array[$x]->[0] $array[$x]->[1]  $array[$y]-
+>[0] $array[$y]->[1]$/";
      }
    }
  }
}

my @arr1 = get_pairs1(@array);
my @arr2 = get_pairs2(@array);

print "====================ROWS$/";
maximize_rows(@arr1);
print "====================NEXT$/";
maximize_rows(@arr2);

__DATA__
2 8 8 8 1 1 1 1 5 5 5 5 7 7 7 7 4 4 4 4 4 4 3 3 3 3 3 3 3 6 6 6 6 6 6 
+6
====================
1 = 1 2
2 = 1 3
3 = 1 4
4 = 1 5
5 = 3 4
6 = 3 5
7 = 3 6
8 = 3 7
9 = 3 8
10 = 4 5
11 = 4 6
12 = 4 7
13 = 4 8
14 = 5 6
15 = 6 7
16 = 6 8
16 counts
1 = 3 6
2 = 4 6
3 = 1 6
4 = 6 7
5 = 5 6
6 = 6 8
7 = 2 6
8 = 3 4
9 = 1 3
10 = 3 7
11 = 3 5
12 = 3 8
13 = 1 4
14 = 4 7
15 = 4 5
16 = 4 8
17 = 1 7
17 counts
====================ROWS
1 = 1 2  3 4
2 = 1 2  3 5
3 = 1 2  3 6
4 = 1 2  3 7
5 = 1 2  3 8
6 = 1 2  4 5
7 = 1 2  4 6
8 = 1 2  4 7
9 = 1 2  4 8
10 = 1 2  5 6
11 = 1 2  6 7
12 = 1 2  6 8
13 = 1 3  4 5
14 = 1 3  4 6
15 = 1 3  4 7
16 = 1 3  4 8
17 = 1 3  5 6
18 = 1 3  6 7
19 = 1 3  6 8
20 = 1 4  3 5
21 = 1 4  3 6
22 = 1 4  3 7
23 = 1 4  3 8
24 = 1 4  5 6
25 = 1 4  6 7
26 = 1 4  6 8
27 = 1 5  3 4
28 = 1 5  3 6
29 = 1 5  3 7
30 = 1 5  3 8
31 = 1 5  4 6
32 = 1 5  4 7
33 = 1 5  4 8
34 = 1 5  6 7
35 = 1 5  6 8
36 = 3 4  5 6
37 = 3 4  6 7
38 = 3 4  6 8
39 = 3 5  4 6
40 = 3 5  4 7
41 = 3 5  4 8
42 = 3 5  6 7
43 = 3 5  6 8
44 = 3 6  4 5
45 = 3 6  4 7
46 = 3 6  4 8
47 = 3 7  4 5
48 = 3 7  4 6
49 = 3 7  4 8
50 = 3 7  5 6
51 = 3 7  6 8
52 = 3 8  4 5
53 = 3 8  4 6
54 = 3 8  4 7
55 = 3 8  5 6
56 = 3 8  6 7
57 = 4 5  6 7
58 = 4 5  6 8
59 = 4 7  5 6
60 = 4 7  6 8
61 = 4 8  5 6
62 = 4 8  6 7
====================NEXT
1 = 3 6  1 4
2 = 3 6  4 7
3 = 3 6  4 5
4 = 3 6  4 8
5 = 3 6  1 7
6 = 4 6  1 3
7 = 4 6  3 7
8 = 4 6  3 5
9 = 4 6  3 8
10 = 4 6  1 7
11 = 1 6  3 4
12 = 1 6  3 7
13 = 1 6  3 5
14 = 1 6  3 8
15 = 1 6  4 7
16 = 1 6  4 5
17 = 1 6  4 8
18 = 6 7  3 4
19 = 6 7  1 3
20 = 6 7  3 5
21 = 6 7  3 8
22 = 6 7  1 4
23 = 6 7  4 5
24 = 6 7  4 8
25 = 5 6  3 4
26 = 5 6  1 3
27 = 5 6  3 7
28 = 5 6  3 8
29 = 5 6  1 4
30 = 5 6  4 7
31 = 5 6  4 8
32 = 5 6  1 7
33 = 6 8  3 4
34 = 6 8  1 3
35 = 6 8  3 7
36 = 6 8  3 5
37 = 6 8  1 4
38 = 6 8  4 7
39 = 6 8  4 5
40 = 6 8  1 7
41 = 2 6  3 4
42 = 2 6  1 3
43 = 2 6  3 7
44 = 2 6  3 5
45 = 2 6  3 8
46 = 2 6  1 4
47 = 2 6  4 7
48 = 2 6  4 5
49 = 2 6  4 8
50 = 2 6  1 7
51 = 3 4  1 7
52 = 1 3  4 7
53 = 1 3  4 5
54 = 1 3  4 8
55 = 3 7  1 4
56 = 3 7  4 5
57 = 3 7  4 8
58 = 3 5  1 4
59 = 3 5  4 7
60 = 3 5  4 8
61 = 3 5  1 7
62 = 3 8  1 4
63 = 3 8  4 7
64 = 3 8  4 5
65 = 3 8  1 7
66 = 4 5  1 7
67 = 4 8  1 7