【python3】leetcode 451. Sort Characters By Frequency (Medium)
阿新 • • 發佈:2019-01-06
451. Sort Characters By Frequency (Medium)
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.
class Solution: def frequencySort(self, s): """ :type s: str :rtype: str """ count = collections.Counter(s) count = collections.OrderedDict(sorted(count.items(),key=lambda t:t[1])) ss = "" for c,num in count.items(): ss = c * num + ss return ss