sub add_edge {
    my (@graph) = @_;
    my $node1 = int(rand(5));
    my $node2 = int(rand(5));
    print "Random node = $node1\n";
    print "Random node = $node2\n";
    my $i, $j;
    if (($node1 ne $node2) and ($graph[$node1][$node2] eq 0)) {
	    $graph[$node1][$node2] = 1;
	    return $graph;
    }
    for ($i = 0; $i < $graph_size; $i++) {
	for ($j = 0; $i < $graph_size; $j++) {
	    if (($graph[$i][$j] eq 0) and ($i ne $j)) {
		$graph[$i][$j] = 1;
		return @graph;
	    }
	}
    }
}