Question

In Perl, how can I test for all possible combinations in a number.
For example, the combination I am interested in is separating.

E.g: 53 could be “5 3” or just “53”
E.g: 215 could be “21 5” or “2 15”

Answer 1

In fact, you are distributing spaces to all the positions between characters. On each position, the space either is realized or not for each combination. Therefore, you can represent it as a binary number, 1 means space present, 0 means space not present.

#!/usr/bin/perl

use warnings;
use strict;

my $num = shift;
my @digits = split //, $num;
my $length = length($num) - 1;

if ($length == 0) {
    print "$num\n";
    exit;
}

for my $i (0 .. 2 ** $length - 1) {
    my $mask = sprintf "%0${length}b", $i;
    my @replace_arr = split //, $mask;
    my $idx = 0;
    for (@replace_arr, '') {
        print $digits[$idx];
        print ' ' if $_;
        $idx++;
    }
    print "\n";
}