old_contents: """Leetcode 720. Longest Word in Dictionary
  Easy
  
  URL: https://leetcode.com/problems/longest-word-in-dictionary/
  
  Given a list of strings words representing an English Dictionary, 
  find the longest word in words that can be built one character at a time by 
  other words in words. If there is more than one possible answer, return the 
  longest word with the smallest lexicographical order.
  
  If there is no answer, return the empty string.
  
  Example 1:
  Input: 
  words = ["w","wo","wor","worl", "world"]
  Output: "world"
  Explanation: 
  The word "world" can be built one character at a time by 
  "w", "wo", "wor", and "worl".
  
  Example 2:
  Input: 
  words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
  Output: "apple"
  Explanation: 
  Both "apply" and "apple" can be built from other words in the dictionary. 
  However, "apple" is lexicographically smaller than "apply".
  
  Note:
  All the strings in the input will only contain lowercase letters.
  The length of words will be in the range [1, 1000].
  The length of words[i] will be in the range [1, 30].
  """
  
  class Solution(object):
      def longestWord(self, words):
          """
          :type words: List[str]
          :rtype: str
  
          Time complexity: O(n), where n is the length of words.
          Space complexity: O(m), where m is the max length of word.
          """
          prefix = longest = ''
          for w in sorted(words):
              if w[:len(w) - 1] == prefix[:len(w) - 1]:
                  prefix = w
                  longest = max([longest, prefix], key=len)
          return longest
  
  
  class SolutionTrie(object):
      def longestWord(self, words):
          """
          :type words: List[str]
          :rtype: str
  
          Time complexity: O(??).
          Space complexity: O(??).
          """
          pass
  
  
  def main():
      # Ans: "world".
      words = ["w","wo","wor","worl", "world"]
      print(Solution().longestWord(words))
  
      # Ans: "apple".
      words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
      print(Solution().longestWord(words))
  
  
  if __name__ == '__main__':
      main()
  
new_contents: """Leetcode 720. Longest Word in Dictionary
  Easy
  
  URL: https://leetcode.com/problems/longest-word-in-dictionary/
  
  Given a list of strings words representing an English Dictionary, 
  find the longest word in words that can be built one character at a time by 
  other words in words. If there is more than one possible answer, return the 
  longest word with the smallest lexicographical order.
  
  If there is no answer, return the empty string.
  
  Example 1:
  Input: 
  words = ["w","wo","wor","worl", "world"]
  Output: "world"
  Explanation: 
  The word "world" can be built one character at a time by 
  "w", "wo", "wor", and "worl".
  
  Example 2:
  Input: 
  words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
  Output: "apple"
  Explanation: 
  Both "apply" and "apple" can be built from other words in the dictionary. 
  However, "apple" is lexicographically smaller than "apply".
  
  Note:
  All the strings in the input will only contain lowercase letters.
  The length of words will be in the range [1, 1000].
  The length of words[i] will be in the range [1, 30].
  """
  
  class Solution(object):
      def longestWord(self, words):
          """
          :type words: List[str]
          :rtype: str
  
          Time complexity: O(nm), where n is the length of words.
          Space complexity: O(m), where m is the max length of word.
          """
          prefix = longest = ''
          for w in sorted(words):
              if w[:len(w) - 1] == prefix[:len(w) - 1]:
                  prefix = w
                  longest = max([longest, prefix], key=len)
          return longest
  
  
  class SolutionTrie(object):
      def longestWord(self, words):
          """
          :type words: List[str]
          :rtype: str
  
          Time complexity: O(??).
          Space complexity: O(??).
          """
          pass
  
  
  def main():
      # Ans: "world".
      words = ["w","wo","wor","worl", "world"]
      print(Solution().longestWord(words))
  
      # Ans: "apple".
      words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
      print(Solution().longestWord(words))
  
  
  if __name__ == '__main__':
      main()
  
subject: Correct time complexity