【LeetCode】451. Sort Characters By Frequency【M】【68】

最新推荐文章于 2022-07-30 00:29:18 发布

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最新推荐文章于 2022-07-30 00:29:18 发布

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分类专栏： leetcode 算法 Python 数据结构排序哈希文章标签： python dict 排序 hash

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本文介绍了一种基于字符出现频率进行排序的算法实现。通过Python示例代码展示如何对字符串中的字符按出现次数从高到低进行排序。适用于需要根据元素出现频次进行排序的应用场景。

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Given a string, sort it in decreasing order based on the frequency of characters.

Example 1:

Input:
"tree"

Output:
"eert"

Explanation:
'e' appears twice while 'r' and 't' both appear once.
So 'e' must appear before both 'r' and 't'. Therefore "eetr" is also a valid answer.

Example 2:

Input:
"cccaaa"

Output:
"cccaaa"

Explanation:
Both 'c' and 'a' appear three times, so "aaaccc" is also a valid answer.
Note that "cacaca" is incorrect, as the same characters must be together.

Example 3:

Input:
"Aabb"

Output:
"bbAa"

Explanation:
"bbaA" is also a valid answer, but "Aabb" is incorrect.
Note that 'A' and 'a' are treated as two different characters.

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对python来说就是dcit的排序问题

class Solution(object):
    def frequencySort(self, s):
        d = {}
        
        for i in s:
            d[i] = d.get(i,0) + 1
            
        l = sorted(d.iteritems(),key = lambda k:k[1],reverse = True)
        
        res = ''
        for (k,v) in l:
            res += k * v
        return res
        
        """
        :type s: str
        :rtype: str
        """