TL;DR

On with TASK #2 from The Weekly Challenge #239. Enjoy!

The challenge

You are given an array of strings and allowed string having distinct characters.

A string is consistent if all characters in the string appear in the string allowed.

Write a script to return the number of consistent strings in the given array.

Example 1

Input: @str = ("ad", "bd", "aaab", "baa", "badab")
       $allowed = "ab"
Output: 2

Strings "aaab" and "baa" are consistent since they only contain characters 'a' and 'b'.

Example 2

Input: @str = ("a", "b", "c", "ab", "ac", "bc", "abc")
       $allowed = "abc"
Output: 7

Example 3

Input: @str = ("cc", "acd", "b", "ba", "bac", "bad", "ac", "d")
       $allowed = "cad"
Output: 4

Strings "cc", "acd", "ac", and "d" are consistent.

The questions

Talking about checking for equality… are accented characters the same as non-accented ones?

The solution

We can do the check using a hash/set and then checking that all characters belong to it.

Perl goes first, we encapsulate the test in a function so that it’s easy to use grep in scalar context to produce the output:

#!/usr/bin/env perl
use v5.24;
use warnings;
use experimental 'signatures';

my $cc = consistency_checker_for(shift);
say scalar grep { $cc->($_) } @ARGV;

sub consistency_checker_for ($string) {
   my %is_allowed = map { $_ => 1 } split m{}mxs, shift;
   return sub ($input) {
      for my $i (0 .. length($input) - 1) {
         return unless $is_allowed{substr($input, $i, 1)};
      }
      return 1;
   };
}

We do almost the same in Raku, just a little change moving the test function inside the function to do the overall test. We could have done like this in Perl as well.

#!/usr/bin/env raku
use v6;
sub MAIN ($allowed, *@str) { put consistent-string($allowed, @str).elems }

sub consistent-string ($allowed, @str) {
   my $al = $allowed.comb.Set;
   my &checker = sub ($input) {
      for $input.comb -> $c {
         return False unless $c ∈ $al;
      }
      return True;
   };
   @str.grep(&checker);
}

Stay safe!