leetcode--720.词典中最长的单词

• 题目：给出一个字符串数组 words 组成的一本英语词典。返回 words 中最长的一个单词，该单词是由 words 词典中其他单词逐步添加一个字母组成。
  若其中有多个可行的答案，则返回答案中字典序最小的单词。若无答案，则返回空字符串。¹

• 示例：

# 示例 1
输入：words = ["w","wo","wor","worl", "world"]
输出："world"
解释： 单词"world"可由"w", "wo", "wor", 和 "worl"逐步添加一个字母组成。
# 示例 2
输入：words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
输出："apple"
解释："apply" 和 "apple" 都能由词典中的单词组成。但是 "apple" 的字典序小于 "apply" 

• 提示：
  1 <= words.length <= 1000
  1 <= words[i].length <= 30
  所有输入的字符串 words[i] 都只包含小写字母。
• 思路：

• 解法一：

class Solution(object):
    def longestWord(self, words):
        """
        :type words: List[str]
        :rtype: str
        """
        words.sort(key=lambda x:(-len(x), x), reverse=True)
        longest = ""
        candidates = {""}
        for word in words:
            if word[:-1] in candidates:
                longest = word
                candidates.add(word)
        return longest

words.sort(key=lambda x:(-len(x), x), reverse=True)解释见链接: https://blog.csdn.net/weixin_46361294/article/details/123682488.

• 解法二–字典树最小：

class Trie:
    def __init__(self):
        self.children = [None] * 26
        self.isEnd = False

    def insert(self, word: str):
        node = self
        for ch in word:
            ch = ord(ch) - ord('a')
            if not node.children[ch]:
                node.children[ch] = Trie()
            node = node.children[ch]
        node.isEnd = True

    def search(self, word: str):
        node = self
        for ch in word:
            ch = ord(ch) - ord('a')
            if node.children[ch] is None or not node.children[ch].isEnd:
                return False
            node = node.children[ch]
        return True

class Solution:
    def longestWord(self, words):
        t = Trie()
        for word in words:
            t.insert(word)
        longest = ""
        for word in words:
            if t.search(word) and (len(word) > len(longest) or len(word) == len(longest) and word < longest):
                longest = word
        return longest

words = ["a", "banana", "app", "appl", "ap", "apply", "apple"]
solution = Solution()
print(solution.longestWord(words))