substrings.rb

# frozen_string_literal: true

# Counts each
def substrings(string, valid_substrings)
  downcase_string = string.downcase
  Hash[
      valid_substrings
      .collect { |substring| [substring, downcase_string.scan(substring).length] }
      .reject { |_substring, substring_length| substring_length.zero? }
  ]
end