[leetcode] 720. Longest Word in Dictionary @ python

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原题

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].

解法

将所有符合条件的单词放入列表, 然后对列表按照字母顺序排序, 选择长度最大的

代码

class Solution(object):
    def longestWord(self, words):
        """
        :type words: List[str]
        :rtype: str
        """
        valid = ['']
        for word in sorted(words, key = lambda x: len(x)):
            if word[:-1] in valid:
                valid.append(word)
        return max(sorted(valid), key = lambda x: len(x))