C - 开关机壳打印案例两次

Question

我写了下面的开关案例。

    char input;
    int run = 1;
    while(run){
        printf("Would you like to update the student's name? Enter Y or N (Y=yes, N=no)\n");
        input = getchar();
        switch (input)
        {
        case 'N':
            run = 0;
            break;
        case 'n':
            run = 0;
            break;
        case 'Y':
            printf("Please enter the updated name\n");
            scanf("%s", st->name);
            run = 0;
            break;
        case 'y':
            printf("Please enter the updated name\n");
            scanf("%s", st->name);
            run = 0;
            break;
        case '\n':
            break;
        default:
            printf("Wrong input. Please enter a valid input (Y or N)\n");
        }
    }

当我运行时，它是这样的：

Please enter the id of the student that you would like to update
1
Would you like to update the student's name? Enter Y or N (Y=yes, N=no)
Would you like to update the student's name? Enter Y or N (Y=yes, N=no)

为什么会打印两次问题？有谁能帮助我吗？除此之外，case的运行符合预期。

Answer 1

函数 getchar 读取所有字符，包括新行字符。而使用

scanf( " %c", &input );

另外你的switch语句有重复的代码。比如说，你可以写

    switch (input)
    {
    case 'N':
    case 'n':
        run = 0;
        break;
    case 'Y':
    case 'y':
        printf("Please enter the updated name\n");
        scanf("%s", st->name);
        run = 0;
        break;
   //...

同样的方法你也可以用在switch语句的其他标签上，并删除这段代码。

    case '\n':
        break;