reverse.rb

def reverse_alternate(string)
  # 1. Break the string down into an array of words.
  words = string.split(' ')
  
  # 2. Loop over each word in the array.
  words.each_with_index do |word, index|
    
      # - if the index is odd, change the word so it is reversed.
      # - if the index is even, leave it as it is.
    word.reverse! if index.odd?
  end
  
  # 3. Join all the words in the array together so they are a string again, with spaces between them.
  # 4. Return the new string we made.
  return words.join(' ')
end

reverse_alternate('one two three four') #=> 'one owt three ruof'