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].

Source: leetcode | Difficulty: EASY
Tags: String algorithms

Sorting

Data structures

Starter code: class Solution:
    def longestWord(self, words: List[str]) -> str:
        

Solutions:
class Solution:

	def longestWord(self, words):
		result = ''
		wordSet = set(words)
		for word in words:
			if (len(word) > len(result) or (len(word) == len(result) and word < result)) and all((word[:i] in wordSet for i in range(1, len(word)))):
				result = word
		return result


class Solution:

	def longestWord(self, words):
		if len(words) == 0:
			return ''
		words.sort(key=lambda x: (len(x), x))
		memo = set()
		maxlen = 0
		maxword = ''
		for word in words:
			if len(word) <= 1:
				memo.add(word)
				maxlen = 1
				if maxword == '':
					maxword = word
			elif word[:-1] in memo:
				memo.add(word)
				if len(word) > maxlen:
					maxlen = len(word)
					maxword = word
		return maxword


class Solution:

	def longestWord(self, words):
		words.sort()
		words_set = set([''])
		longest = ''
		for word in words:
			if word[:-1] in words_set:
				words_set.add(word)
				if len(word) > len(longest):
					longest = word
		return longest


class Solution:

	def longestWord(self, words):
		wset = set([''])
		ans = ''
		for word in sorted(words):
			if word[:-1] in wset:
				wset.add(word)
				if len(word) > len(ans):
					ans = word
		return ans


class Solution:

	def longestWord(self, words):
		valid = {''}
		for word in sorted(words):
			if word[:-1] in valid:
				valid.add(word)
		return max(sorted(valid), key=len)


class Solution:

	def longestWord(self, words):
		words.sort()
		longest_word = ''
		word_list = list()
		words_set = set([''])
		for word in words:
			if word[:-1] in words_set:
				words_set.add(word)
				if len(longest_word) < len(word):
					longest_word = word
		return longest_word


class Solution:

	def longestWord(self, words):
		(ret, m) = ('', {''})
		for w in sorted(words):
			if w[:-1] in m:
				m.add(w)
				ret = max(ret, w, key=len)
		return ret


class Solution:

	def longestWord(self, words):
		wordSet = set(words)
		words.sort(key=lambda c: (-len(c), c))
		for word in words:
			if all((word[:k] in wordSet for k in range(1, len(word)))):
				return word
		return ''