Robbie Hatley's Solutions To The Weekly Challenge #278

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, cycling every Sunday. You can find it here:

The Weekly Challenge

The Weekly Challenge for the week of 2024-07-14 through 2024-07-20 is #278. Its tasks are as follows:

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Task 278-1: Sort String
Submitted by: Mohammad Sajid Anwar
Given a shuffled string, write a script to return the sorted
string. A string is shuffled by appending word position to
each word.

Example 1 input:
"and2 Raku3 cousins5 Perl1 are4"
Expected output: "Perl and Raku are cousins"

Example 2 input:
"guest6 Python1 most4 the3 popular5 is2 language7"
Expected output: "Python is the most popular guest language"

Example 3 input:
"Challenge3 The1 Weekly2"
Expected output: "The Weekly Challenge"

My approach was to do this:

1. Split the string by whitespace to array of tokens "@raw_tok".
2. Sort "@raw_tok" to array "@srt_tok" by unicode codepoint of the last character.
3. Join with spaces a map of "@srt_tok" with the last character of each token removed.

But then I realized, I don't need any of the intermediates, and this is best written in reverse order, as a purely "functional" subroutine:

   use v5.38;
   use utf8;
   sub sort_string ($string) {
      join ' ',
      map {substr $_, 0, length($_) - 1}
      sort {ord substr($a, -1, 1) <=> ord substr($b, -1, 1)}
      split /\s+/, $string
   }

Robbie Hatley's Perl Solution to The Weekly Challenge 278-1

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Task 278-2: Reverse Word
Submitted by: Mohammad Sajid Anwar
Given a word, $word and a character, $char, write a script to
replace the substring up to and including $char with its
characters sorted alphabetically. If $char doesn’t exist in
$word then don't do anything.

Example 1 input:
["challenge", "e"],
Expected output: "acehllnge"

Example 2 input:
["programming", "a"],
Expected output: "agoprrmming"

Example 3 input:
["champion", "b"],
Expected output: "champion"

I solve this by using a programmatic substitution with a "minimal" quantifier "*?":

   use v5.38;
   use utf8;
   sub sort_string ($string, $char) {
      $string =~ s{^(.*?$char)}{join '', sort split //, $1}er;
   }

Robbie Hatley's Perl Solution to The Weekly Challenge 278-2

That's it for challenge 278; see you on challenge 279!