use v5.12;
use warnings;
use Data::Dump qw/pp dd/;


# https://perlmonks.org/?node_id=11141490

calc($_) for 5..10;

exit;


sub rotate(\@) {
    my $r = shift @{$_[0]};
    push @{$_[0]},$r
}

sub get_edges {
    my @verts  = @{+shift};
    my $center = shift;

    my $left  = $#verts/2;
    my @res = map [ $verts[$_-1], $verts[-$_] ], 1..$left;
    push @res,[$center,$verts[$left]]
      if defined $center;
    return \@res;
}

sub get_matrix{
    my (@colored) = @_;
    my @inc_matrix;
    while ( my ($color,$color_set) = each @colored ) {
        for my $edge (@$color_set) {
            my ($v0,$v1) = @$edge;
            $inc_matrix[ $v0 ][ $v1 ] = $color;
            $inc_matrix[ $v1 ][ $v0 ] = $color;
        }
    }
    return \@inc_matrix;
}

sub calc {
    my ( $n ) = @_ ;
    my @nodes = 0 .. $n-1;

    my $center = $n%2
      ? undef
        : pop @nodes;

    my @colored;
    for (@nodes) {
        push @colored, get_edges(\@nodes, $center);
        rotate(@nodes);
    }

    say "\n";
    print "="x10;
    say " N=$n";
    say "=== Colors: ", scalar @colored;
    say "=== Edges: ";
    say pp \@colored;
    say "=== Color Matrix:";
    say pp get_matrix(@colored);
}