c - 案例循环有问题

Question

请。我想要显示从“A”到“H”的选项，但是“默认无效选项”一直出现。我如何防止出现“默认无效选项”。如果你能帮助我，非常感谢。

void disp3Ave (void)
{
    int day, total;
    char j;
    extern float PSI23ave[];
    extern float PSI24ave[];
    extern float PSI25ave[];
    float average;
    total=0;
    printf("Day 23 or 24?\n");
    scanf("%\d", &day);

    if(day == 23)
    {
        printf("A: 0300.\n");
        printf("B: 0600.\n");
        printf("C: 0900.\n");
        printf("D: 1200.\n");
        printf("E: 1500.\n");
        printf("F: 1800.\n");
        printf("G: 2100.\n");
        printf("H: 0000.\n");
        scanf("%c", &j);

        switch (j)
        {
            case 'a':
            case 'A': total= PSI23ave[3] + PSI23ave[4] + PSI23ave[5];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'b':
            case 'B': for (j=0;j<24;j++) total= PSI23ave[6] + PSI23ave[7] + PSI23ave[8];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'c':
            case 'C': for (j=0;j<24;j++) total= PSI23ave[9] + PSI23ave[10] + PSI23ave[11];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'd':
            case 'D': for (j=0;j<24;j++) total= PSI23ave[12] + PSI23ave[13] + PSI23ave[14];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'e':
            case 'E': for (j=0;j<24;j++) total= PSI23ave[15] + PSI23ave[16] + PSI23ave[17];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'f':
            case 'F': for (j=0;j<24;j++) total= PSI23ave[18] + PSI23ave[19] + PSI23ave[20];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'g':
            case 'G': for (j=0;j<24;j++) total= PSI23ave[21] + PSI23ave[22] + PSI23ave[23];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;
            case 'h':
            case 'H': for (j=0;j<24;j++) total= PSI24ave[0] + PSI24ave[1] + PSI24ave[2];
                  average = total/3;
                  printf("3-hr average = %.1f\n", average);
                  break;

            default: printf("Invalid option.\n");
                 break;

        }
    }

提前致谢!干杯!

Answer 1

看起来当您为 int 变量 day 输入值时，字符 '\n' 保留在输入缓冲区中。
这将存储在您的变量 j 中，因此您会得到 Invalid option。

编辑:你可以试试 scanf("\n%c", &j);