old_contents: #!/usr/bin/env python
  
  import sys
  
  
  # O(n^4) approach: generate all possible substrings and
  # compare each for equality.
  
  def longest_duplicated_substring(string):
      """Return the longest duplicated substring.
  
      Keyword Arguments:
      string -- the string to examine for duplicated substrings
  
      This approach examines each possible pair of starting points
      for duplicated substrings. If the characters at those points are
      the same, the match is extended up to the maximum length for those
      points. Each new longest duplicated substring is recorded as the
      best found so far.
  
      This solution is optimal for the naive brute-force approach and
      runs in O(n^3).
      """
      lds = ""
      string_length = len(string)
      for i in range(string_length):
          for j in range(i+1,string_length):
              # Alternate approach with while loop here and max update outside.
              # Can also break length check into function.
              for substring_length in range(string_length-j):
                  if string[i+substring_length] != string[j+substring_length]:
                      break
                  elif substring_length + 1 > len(lds):
                      lds = string[i:i+substring_length+1]
      return lds
  
  if __name__ == "__main__":
      print(longest_duplicated_substring(' '.join(map(str, sys.argv[1:]))))
  
new_contents: #!/usr/bin/env python
  
  import sys
  
  
  def longest_duplicated_substring(string):
      """Return the longest duplicated substring.
  
      Keyword Arguments:
      string -- the string to examine for duplicated substrings
  
      This approach examines each possible pair of starting points
      for duplicated substrings. If the characters at those points are
      the same, the match is extended up to the maximum length for those
      points. Each new longest duplicated substring is recorded as the
      best found so far.
  
      This solution is optimal for the naive brute-force approach and
      runs in O(n^3).
      """
      lds = ""
      string_length = len(string)
      for i in range(string_length):
          for j in range(i+1,string_length):
              for substring_length in range(string_length-j):
                  if string[i+substring_length] != string[j+substring_length]:
                      break
                  elif substring_length + 1 > len(lds):
                      lds = string[i:i+substring_length+1]
      return lds
  
  if __name__ == "__main__":
      print(longest_duplicated_substring(' '.join(map(str, sys.argv[1:]))))
  
subject: Move todos into issues tracking on GitHub