C：Do-While 循环重复太多！

我有一个让我困惑的小程序。我正在尝试使用循环来获取用户的输入。如果输入错误，则再次重复，如果正确，则退出。 代码片段是：

void main()
{
    char user_status; // Checks User Status q = Quiz Master and p = Participant
    int valid_status = '0'; // Checks If User Status Is Valid Or Not. Used In Some Loops. 0 = Invalid, 1 = Invalid.
    printf("Welcome to General Knowledge Quiz Management System.\nThis application has been designed to help you conduct a quiz or test your GK.");
    do
    {
        user_status = '0';
        printf("\n\nPlease enter your role.\nQuiz Master = \'q\'\nParticipant = \'p\'\n");
        scanf("%c", &user_status);
        if (user_status == 'q'|| user_status == 'Q')
        {
            printf("Initializing Quiz Master Segment\n\n________________________________\n");
            initiate_qm();
            valid_status = '1';
        }
        else if (user_status == 'p' || user_status == 'P')
        {
            printf("Initializing Participant Segment");
            initiate_pa();
            valid_status = '1';
        }
    }
    while (valid_status != '1')
        printf("\nProgram Will Exit Now. Press Any Key To Return To Windows.");
    getch();
}

因为你给了 scanf 三个字符来处理。它在第一次调用 scanf 获取“a”时删除第一个第一个字符，但在标准输入缓冲区中仍然保留“bc”。

在再次寻找输入之前，您需要检查缓冲区中是否有剩余的内容。我会避免刷新标准输入缓冲区，因为它是未定义的行为。 (http://www.gidnetwork.com/b-57.html)

您可以读取剩余的字符并丢弃它们

do{  
    scanf("%c", &user_status);  
}while(user_status!='\n'); //This discards all characters until you get to a newline

当你读完你想要的角色后。