题解 | #字符串排序#

def str_sort(s):
    N = len(s)
    res = []
    letters = []
    for i in s:
        # 判断是否是字母，可用if 'a' <= i.lower() <= 'z'代替，下面的同上
        if i.isalpha():
            letters.append(i)
    # 忽略大小写的排序
    sorted_letters = sorted(letters, key=str.lower)
    index = 0
    for i in range(N):
        if s[i].isalpha():
            res.append(sorted_letters[index])
            index += 1
        else:
            res.append(s[i])
    return "".join(res)

if __name__ == "__main__":
    while True:
        try:
            s = input()
            print(str_sort(s))
        except:
            break