Brute force de Bruijn

brute-force-de-bruijn.pl

use 5.010;
use warnings;
use strict;

my $N = 10;
my $L = 4;

my $num_possible_combs = $N ** $L;
my $string = join '', map { int($N * rand) } 1..$L-1;
my %combs;

DIGIT:
while (keys(%combs) < $num_possible_combs) {
    my @all_combs = ('');
    for my $add_length (1..$L) {
        sub pick_star {
            map { $_->[0] }
            sort { $a->[1] <=> $b->[1] }
            map { [$_, rand()] } @_
        }
        @all_combs = map { my $s = $_; map { $s.$_ } 0..$N-1 } @all_combs;
        my @numbers_in_some_order = pick_star(@all_combs);
        for my $addition (@numbers_in_some_order) {
            my $resulting_comb = substr($string, -$L+$add_length) . $addition;
            if (!exists $combs{$resulting_comb}) {
                ++$combs{$resulting_comb};
                $string .= $addition;
                next DIGIT;
            }
        }
    }
}
say $string;