How my string segmenting program works

We were tasked with created a program that split up a string into individual words. For example "catsurethra" should be split up into "cats" & "urethra". However, you’ll notice that there are other words inside of that string like "cat", "at", and "sure". I needed to make sure I accounted for all possible words that my program would find and also ensure that there were no leftover letters at the end. After some sketching out of ideas into plain text, I felt I had a working concept.

1. First, I linked my code to the dictionary I created and created storage containers for all of my method’s needs:

require_relative '../lib/dictionary.rb'

def segment_string(str)
  word_index = Hash.new(0)
  first_letter= 0
  last_letter = 0

2. Then I started my loop which says that while the variable is less than or equal to the string length, do the following operation:

  while last_letter <= str.length do

3. If there are danglers (or letters left over that do not form a word), take the value of the previous last letter and add one to it. Then delete the key/value pair with highest value:

  if danglers?(str, first_letter, last_letter)
    last_letter = change_value_of_letter_variable

4. If there is no previous word, then you need to start over at 0. But if there is a previous word, take the value of the previous word’s last letter and add 1:

  if you_just_deleted_the_first_word_in_hash
    first_letter = 0
    first_letter = change_value_of_letter_variable

5. If the current collection of characters is not a word, add one to the last_letter variable:

  elsif !valid_word?(str[first_letter..last_letter])
    last_letter += 1

6. If the collection of characters is a word, store the word & index pair in the hash:

elsif valid_word?(str[first_letter..last_letter])
  word_index[str[first_letter..last_letter]] = last_letter	

7. Then move on to the next character by reassigning the last_letter +1 to the first_letter spot and adding one to the last_letter:

    first_letter = last_letter + 1
    last_letter += 1

8. Then return the keys from the hash:

  return $word_index.keys

My other methods work as follows:

A. Check if the current value of last_letter is the same as the value of the length of the string AND if the length of the joined array is less than the length of the original string:

def danglers?(str, first_letter, last_letter)
  last_letter == str.length && $word_index.keys.join.length < str.length

B. Take the value of the previous last letter and add one to it:

def change_value_of_letter_variable
  return $word_index.values.max + 1

C. Delete the previous word and it’s value from the Hash:

def delete_from_hash
  $word_index.delete($word_index.max_by{|k,v| v}[0])

D. If the first word of the Hash was the one that you deleted. Conditional stating that now the max value in the Hash is nil.

def you_just_deleted_the_first_word_in_hash
  $word_index.values.max == nil