Perl solution to challenge 67 task 2

My solution uses recursion to loop over all the possible values

1 files changed, 41 insertions, 0 deletions

diff --git a/challenge-067/walt-mankowski/perl/ch-2.pl b/challenge-067/walt-mankowski/perl/ch-2.pl
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+#!/usr/bin/env perl
+use strict;
+use warnings;
+use feature qw(:5.30);
+use experimental qw(signatures);
+
+# 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.
+
+# store the letters for each digit as a hash of arraryrefs
+my %key = (1 => [qw(_ @)],
+           2 => [qw(A B C)],
+           3 => [qw(D E F)],
+           4 => [qw(G H I)],
+           5 => [qw(J K L)],
+           6 => [qw(M N O)],
+           7 => [qw(P Q R S)],
+           8 => [qw(T U V)],
+           9 => [qw(W X Y Z)],
+           0 => [' ']
+          );
+
+my $s = $ARGV[0];
+gen_combs($s, 0, '');
+
+# generate the combinations by using recursion to loop over all the
+# possible values
+sub gen_combs($s, $idx, $prefix) {
+    if ($idx == length($s)) {
+        say $prefix;
+    } else {
+        my $digit = substr($s, $idx, 1);
+        for my $c ($key{$digit}->@*) {
+            gen_combs($s, $idx+1, $prefix . $c);
+        }
+    }
+}