레벨2 문제
from collections import Counter
def solution(s):
arr = []
for i in s:
if (i.isdigit() or i == ','):
arr.append(i)
arr = "".join(arr)
arr = list(map(int, arr.split(',')))
cnt = Counter(arr)
cnt = sorted(cnt.items(), reverse=True, key = lambda x:x[1])
arr = []
for key, value in cnt:
arr.append(key)
answer = arr
return answer