Max word letter span problem

solution.rb

# Given some text, write a function to find the max word letter span and list of words with that span

# Word letter span is defined as the alphabetical distance in between the first and last letters of the word

# Rules
# The same two letters produce the same span regardless of their order in the word
#.    “PAT” and “TAP” have span 4  
# Capitalization does not matter
#.    “Pat” and “pat” have span 4
# Words that begin and end with the same letter have a word span of 0
#.    “pop” and “I” have span 0

# Examples
# "pat" -> 'p' to 't' = 4
# "Float" -> 'f' to 't' = 14
# "wood" -> 'w' to 'd' = abs(-19) = 19
# "would" -> 'w' to 'd' = 19
# "I" -> 'I' to 'I' = 0
# "pop" -> 'p' to 'p' = 0

# Output from this function should be the span and the list of words with that span

# Given: “I would trade two wood for a sheep but not three wood."
# Expect: 19, ["would", "wood"] or 19, ["wood", "would"] 

def word_span(word)
  abc_indexes = ("a".."z").to_a

  chars = word.downcase.chars

  first_letter = chars.first
  last_letter = chars.last

  distance = abc_indexes.find_index(first_letter) - abc_indexes.find_index(last_letter)
  distance.positive? ? distance : distance * -1
end

def sentence_span(sentence)
  words = sentence.split(/\W/).uniq

  word_spans = words.map { |word| [word_span(word), word] }
  max_span = word_spans.map(&:first).max

  word_spans
    .select { |ws| ws[0] == max_span }
    .reduce({}) do |hash, ws|
      key, val = ws

      hash[key.to_s] ||= []
      hash[key.to_s] << val

      hash
    end
end

# Test the function
puts word_span("pat") == 4
puts word_span("Float") == 14
puts word_span("wood") == 19
puts word_span("doow") == 19
puts word_span("I") == 0
puts word_span("pop") == 0

puts(sentence_span('I would trade two wood for a sheep but not three wood.') == {"19"=>["would", "wood"]})