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use strict;
use warnings;
use feature qw'say signatures';
no warnings 'experimental::signatures';
use List::Util qw(reduce);
use constant DEBUG => $ENV{DEBUG} // 0;
run() unless caller();
sub run() {
my $m = prompt_for_integer('m');
my $n = prompt_for_integer('n');
my @possible_integers = numbers_from_digits($m);
my @divisible_by_n = grep { $_ % $n == 0 } @possible_integers;
explain( $m, $n, \@possible_integers, \@divisible_by_n ) if DEBUG;
say scalar @divisible_by_n;
}
sub explain ( $m, $n, $possible_integers, $divisible_by_n ) {
say "Possible integers created using the digits of $m are:";
say join( ', ', sort { $a <=> $b } @$possible_integers );
say "There are "
. scalar(@$divisible_by_n)
. " integers divisible by $n such as:";
say join( ', ', sort { $a <=> $b } @$divisible_by_n );
}
sub numbers_from_digits($x) {
my @digits = split( '', $x );
my $numbers = reduce(
sub {
my $digit = $digits[$b];
return [
@$a, #
$digit,
( grep { length $_ < @digits } map { $_ . $digit } @$a ),
];
},
[],
0 .. $#digits
);
return @$numbers;
}
sub prompt_for_integer($name) {
say "Enter positive integer '$name'";
chomp( my $number = <STDIN> );
if ( $number !~ m/^\d+$/ || $number < 1 ) {
say "Invalid integer.";
return prompt_for_integer($name);
}
return $number;
}
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