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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