# 720. Longest Word in Dictionary 词典中最长的单词

@TOC

## # 题目描述

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:

1. All the strings in the input will only contain lowercase letters.
2. The length of words will be in the range [1, 1000].
3. The length of words[i] will be in the range [1, 30].

## # 解题方法

### # 暴力查找

class Solution(object):
def longestWord(self, words):
"""
:type words: List[str]
:rtype: str
"""
wset = set(words)
res = ""
for w in words:
isIn = True
for i in range(1, len(w)):
if w[:i] not in wset:
isIn = False
break
if isIn:
if not res or len(w) > len(res):
res = w
elif len(w) == len(res) and res > w:
res = w
return res

### # 排序

class Solution(object):
def longestWord(self, words):
"""
:type words: List[str]
:rtype: str
"""
words.sort()
res = set([''])
longestWord = ''
for word in words:
if word[:-1] in res: