720. Longest Word in Dictionary 题目有坑

taoqick

于 2021-07-12 23:36:56 发布

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这是一个关于字符串处理的问题，目标是从给定的英语字典数组中找到可以按字符逐个构建的最长单词，并确保每个单词都可以由之前的单词逐步构建。在示例中，给出的解决方案首先对输入数组进行排序，然后通过遍历并检查每个单词是否可以由前一个单词加一个字符构成，来找到符合条件的最长单词。如果存在多个答案，返回字典序最小的那个。

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Given an array of strings words representing an English Dictionary, return 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".

Constraints:

1 <= words.length <= 1000
1 <= words[i].length <= 30
words[i] consists of lowercase English letters.

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题目并没有强调从空串开始，有个坑：

class Solution:
    def longestWord(self, words: List[str]) -> str:
        words.sort()
        wset,longest = {''},''
        for word in words:
            if word[:-1] in wset:
                wset.add(word)
                if len(word) > len(longest):
                    longest = word
        return longest