题解 | #字符统计#
https://www.nowcoder.com/practice/c1f9561de1e240099bdb904765da9ad0
s = input()
d = {}
res = sorted(set(s)) # 提取出字母并排序
for i in res:
d[i] = s.count(i) # 统计每个字母出现的次数并追加到字典
s = sorted(set(d.values()),reverse=True) # 次数降序排列
for i in s:
for j in res:
if d[j] == i:
print(j, end="")