reverse_words.rb

def reverse_words(message) 
  # first we reverse all the characters in the entire message 
  reverse_characters(message, 0, message.length-1) 
  # this gives us the right word order 
  # but with each word backwards 
  # now we'll make the words forward again 
  # by reversing each word's characters 
  # we hold the index of the /start/ of the current word 
  # as we look for the /end/ of the current word 
  current_word_start_index = 0 
  for i in 0..message.length 
  # found the end of the current word! 
    if (message[i] == ' ') || (i == message.length) 
      reverse_characters(message, current_word_start_index, i-1) 
      # if we haven't exhausted the string our # next word's start is one character ahead 
      current_word_start_index = i + 1 
    end 
  end 
  
  return message
end

def reverse_characters(message, front_index, back_index) 
  # walk towards the middle, from both sides 
  while front_index < back_index 
  # swap the front char and back char 
    message[front_index], message[back_index] = message[back_index], message[front_index] 
    front_index += 1 
    back_index  -= 1 
  end 

  return message
end

message = 'find you will pain only go you recordings security the into if'
puts reverse_words(message)