PAT (Basic Level) Practice （中文）1029 旧键盘

题目

if __name__ == '__main__':
    str1 = input()
    str2 = input()
    res = []
    j = 0
    for i in range(len(str1)):
        if j < len(str2) and str1[i] == str2[j]:
            j += 1
        elif str1[i].upper() not in res:
            res.append(str1[i].upper())
    print("".join(res))