leetcode692-- Top K Frequent Words.

leetcode692-- Top K Frequent Words.

题目


Given a non-empty list of words, return the k most frequent elements.

Your answer should be sorted by frequency from highest to lowest. If two words have the same frequency, then the word with the lower alphabetical order comes first.

Example 1:

Input: ["i", "love", "leetcode", "i", "love", "coding"], k = 2
Output: ["i", "love"]
Explanation: "i" and "love" are the two most frequent words.
    Note that "i" comes before "love" due to a lower alphabetical order.

Example 2:

Input: ["the", "day", "is", "sunny", "the", "the", "the", "sunny", "is", "is"], k = 4
Output: ["the", "is", "sunny", "day"]
Explanation: "the", "is", "sunny" and "day" are the four most frequent words,
    with the number of occurrence being 4, 3, 2 and 1 respectively.

Note:

    You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
    Input words contain only lowercase letters.

Follow up:

    Try to solve it in O(n log k) time and O(n) extra space.


解答

这个题目感觉仍然可以用桶排序的办法,然后需要用到python里的内建的sort函数, 对字符串进行排序的,python里的set函数并不具有自动排序的功能。

class Solution(object):
    def topKFrequent(self, words, k):
        """
        :type words: List[str]
        :type k: int
        :rtype: List[str]
        """
        
        dic = {}
        for x in words:
            try:
                dic[x] += 1
            except:
                dic[x] = 1
                
        
        bucket = [[] for _ in range(len(words))]
        
        for key, value in dic.items():
            bucket[value].append(key)
            
        ret = []
        
        for i in range(len(words)-1, -1, -1):
            if len(bucket[i]) >1:
                bucket[i].sort()  ## python 的sort不具有自动排序的功能。
                ret += bucket[i]
            elif len(bucket[i])==1:
                ret += bucket[i]
            else:
                continue
                
            if len(ret)>=k:
                return ret[:k]
        
        return None

打赏,谢谢~~

取消

感谢您的支持,我会继续努力的!

扫码支持
扫码打赏,多谢支持~

打开微信扫一扫,即可进行扫码打赏哦