https://programmers.co.kr/learn/courses/30/lessons/12917
def solution(s):
answer = ''
mlist=[]
for i in s:
mlist.append(i)
mlist.sort(reverse=True)
for i in mlist:
answer+=i
return answer
def solution(s):
return ''.join(sorted(s, reverse=True))
join
: 문자열 합쳐서 반환