Longest Word

In Doc2Doc, we have a search function to find the longest word in a document.

Assignment

Complete the find_longest_word function without a loop. It accepts string inputs, document, and optional longest_word, which is the current longest word and defaults to an empty string.

• Check if the first word is longer than the current longest_word, then recur for the rest of the document.

• Ensure there are no potential index errors.

Assume that a "word" means a series of any consecutive non-whitespace characters. For example, longest_word("How are you?") should return the string "you?".

Solution

def find_longest_word(document, longest_word=""):

    # Case block, if the len of document is 0, return the longest word
    if len(document) == 0:
        return longest_word

    # Split doc to give us first word, and then rst of string
    words = document.split(maxsplit=1)

    if len(words)>=1:
        if len(words[0]) > len(longest_word):
            longest_word = words[0]

        if len(words) > 1:
            return find_longest_word(words[1], longest_word)
    return longest_word

Explanation

• Function Signature:

  def find_longest_word(document, longest_word=""):

  • Purpose:

    • Searches through the document string to determine the longest word.

  • Parameters:

    • document: The remaining text to search through.

    • longest_word: The current longest word found (defaults to an empty string).

---

• Base Case:

  if len(document) == 0:
      return longest_word

  • Explanation:

    • If the document is empty, there's nothing left to search.

    • Callout: The recursion stops here and returns the longest word found so far.

---

• Splitting the Document:

  words = document.split(maxsplit=1)

  • Explanation:

    • Splits the document into a list of words, but only into two parts:

      • The first word.

      • The rest of the document (everything after the first word).

  • Callout: This ensures we only work with one word at a time and pass the remainder to the next recursive call, avoiding loops.

---

• Checking and Updating the Longest Word:

  if len(words) >= 1:
      if len(words[0]) > len(longest_word):
          longest_word = words[0]

  • Explanation:

    • If there is at least one word:

      • Compare the length of the first word (words[0]) with the current longest_word.

      • Update longest_word if the first word is longer.

  • Callout: This conditional is the key comparison step to determine which word is longer.

---

• Recursion for the Rest of the Document:

  if len(words) > 1:
      return find_longest_word(words[1], longest_word)

  • Explanation:

    • If there is more than one element in words, it means there is a remainder of the document.

    • Recursively call find_longest_word on the remaining text (words[1]), passing along the updated longest_word.

  • Callout: This is the recursive step that processes the rest of the document one word at a time.

---

• Final Return:

  return longest_word

  • Explanation:

    • If no remainder is found (i.e., words contains only one word), return the current longest_word.

  • Callout: This covers the case where the document was just one word, or when we've processed all words.