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#!/usr/bin/env perl
use strict;
use warnings;
use 5.016;
sub factorial {
my ($n) = @_;
return 1 if $n < 2;
return $n * factorial($n - 1);
}
sub permutations {
my ($n) = @_;
my $string = join('', 1..$n);
return map { _permutation($string, $_) } 0..(factorial($n) - 1);
}
sub _permutation {
my ($string, $index) = @_;
return '' if $string eq '';
my $fact = factorial(length($string) - 1);
my $current_index = int($index / $fact);
my $rest = $index % $fact;
my $first_digit = substr($string, $current_index, 1);
substr($string, $current_index, 1, '');
return $first_digit . _permutation($string, $rest);
}
my $n = <>;
say factorial($n);
say join(' ', split '') for permutations($n);
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