题解 | 禁止重复注册

current_users = ["Niuniu", "Niumei", "GURR", "LOLO"]
new_users = ["GurR", "Niu Ke Le", "LoLo", "Tuo Rui Chi"]

for name in new_users:
    flag = False
    for user in current_users:
        if name.lower() == user.lower():
            print(
                f"The user name {name} has already been registered! Please change it and try again!"
            )
            flag = True
            break
    if flag == False:
        print(f"Congratulations, the user name {name} is available!")