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#! /opt/local/bin/perl
#
# hooked_on_phonics.pl
#
# TASK #2 › Letter Phone
# Submitted by: Mohammad S Anwar
#
# You are given a digit string $S. Write a script to print all
# possible letter combinations that the given digit string could
# represent.
#
# Letter Phone
# 2 --> ABC
# 3 --> DEF
# 4 --> GHI
# 5 --> JKL
# 6 --> MNO
# 7 --> PQRS
# 8 --> TUV
# 9 --> WXYZ
#
#
# Example:
# Input: $S = '35'
#
# Output: ["dj", "dk", "dl", "ej", "ek", "el", "fj", "fk", "fl"].
#
# 2020 colin crain
## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
use warnings;
use strict;
use feature ":5.26";
## ## ## ## ## MAIN:
my $input = $ARGV[0] // '5273';
$input =~ s/\W//g; ## tolerate phone number formats, strip punct chars
($input =~ /[^2-9]/) and
die "only numbers between 2 through 9 can be alphabetized\n";
my @digits = split //, $input;
my %encode = ( 2 => ["a", "b", "c"],
3 => ["d", "e", "f"],
4 => ["g", "h", "i"],
5 => ["j", "k", "l"],
6 => ["m", "n", "o"],
7 => ["p", "q", "r", "s"],
8 => ["t", "u", "v"],
9 => ["w", "x", "y", "z"] );
my $list = $encode{(shift @digits)};
my @list = make_strings(\%encode, \@digits, $list)->@*;
say $_ for @list;
## ## ## ## ## SUBS:
sub make_strings {
my ($encode, $digits, $list) = @_;
return $list unless $digits->@*;
my @newlist = ();
my $digit = shift $digits->@*;
for my $str ( $list->@* ) {
for ( $encode->{$digit}->@* ) {
push @newlist, $str . $_;
}
}
return make_strings( $encode, $digits, \@newlist);
}
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