描述
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.
解析
根据题意，只需要使用内置的函数 Counter 来统计字符串中的字符及其出现频率，然后按照频率从大到小在遍历字符串的时候，将字符按照出现的频率依次拼接即可得到答案。
解答
class Solution(object):
def frequencySort(self, s):
"""
:type s: str
:rtype: str
"""
r = ""
c = collections.Counter(s)
for k,v in c.most_common(len(c)):
r += k*v
return r
运行结果
Runtime: 64 ms, faster than 38.84% of Python online submissions for Sort Characters By Frequency.
Memory Usage: 15.7 MB, less than 71.53% of Python online submissions for Sort Characters By Frequency.
原题链接：leetcode.com/problems/so…
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