Update supported versions of Ruby

.github/workflows/exercise-tests.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         os:
           - ubuntu-24.04
-        ruby-version: [3.2, 3.3]
+        ruby-version: [3.3, 3.4]
 
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1

README.md

@@ -19,9 +19,11 @@ Exercism Exercises in Ruby
 
 ## Setup
 
-You'll need a recent (2.6+) version of Ruby, but that's it.
+You will want a recent (3.4+) version of Ruby, but that's it.
 Minitest ships with the language, so you're all set.
 
+Older versions of Ruby may work, but are not officially supported.
+
 ## Anatomy of an Exercise
 
 The files for an exercise live in `exercises/<slug>`.

exercises/practice/parallel-letter-frequency/.meta/example.rb

@@ -1,10 +1,34 @@
 class ParallelLetterFrequency
   def self.count(texts)
-    ractors = (0...texts.length).map do |i|
-      Ractor.new(texts[i]) do |text|
-        text.downcase.each_grapheme_cluster.select do |cluster|
-          cluster.match?(/\p{Alpha}/)
-        end.tally
+    return {} if texts.empty?
+
+    ractor_count = [texts.length, 8].min
+    batch_size = (texts.length.to_f / ractor_count).ceil
+    ractors = texts.each_slice(batch_size).map do |batch|
+      Ractor.new(batch) do |batch_texts|
+        ascii_counts = Array.new(26, 0)
+        tally = Hash.new(0)
+
+        batch_texts.each do |text|
+          if text.ascii_only?
+            text.each_byte do |byte|
+              case byte
+              when 65..90 then ascii_counts[byte - 65] += 1
+              when 97..122 then ascii_counts[byte - 97] += 1
+              end
+            end
+          else
+            text.downcase.each_grapheme_cluster do |cluster|
+              tally[cluster] += 1 if cluster.match?(/\p{Alpha}/)
+            end
+          end
+        end
+
+        ascii_counts.each_with_index do |count, index|
+          tally[(index + 97).chr] += count unless count.zero?
+        end
+
+        tally
       end
     end