>>616 Perl5
use List::Util max;
use feature say;
for (<DATA>) {
@a = split;
$n = max map{length} @a;
say $n;
$b = join '', sort map{$_.'a'x($n-length)} @a;
$b =~ s/a//g;
say $b;
}
__DATA__
3 2 1
1 2 21
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

実行
$ perl 12_614.pl
123
1212
10111213141516123456789