c - switch 语句即使在 break 之后也执行 case 2

Question

当情况 1 时，程序会执行预期的代码，但当它询问您是否要再次计算体积时，如果您选择是，它只会执行情况 2。我不确定哪里出了问题。除非您在菜单中选择 2，否则如何让它只执行情况 1？

        #include <stdio.h>
        #include <stdlib.h>

        int main()
        {
            float menu1, opt1, opt2, opt3, opt4, t;
            int td;

            printf("Enter: ");
            scanf("%d",&td);
        switch(td) {
            case 1:
            printf("Enter a, b, c, and h of the triangular prism in meters\n\n");
            printf("a ");
            scanf("%f", &opt1);
            printf("b ");
            scanf("%f", &opt2);
            printf("c ");
            scanf("%f", &opt3);
            printf("h ");
            scanf("%f", &opt4);
            printf("\nWould you like to make another Volume calculation (1 for Yes, 2 for No)?");
            scanf("%f", &menu1);
            if (menu1 == 2) {
                t = 0;
                break;
            }
            if (menu1 < 1 || menu1 > 2) {
                printf("\n\nUser choice must be between 1 and 2!\n\n");
                printf("Would you like to make another Volume calculation (1 for Yes, 2 for No)?");
                scanf("%f", &menu1);
                if(menu1 == 2) {
                   t = 0;
                   break;
                }
            }

        case 2:
            printf("Enter a and h of the triangular pyramid\n\n");
            printf("a ");
            scanf("%f", &opt1);
            printf("h ");
            scanf("%f", &opt2);
            printf("\nWould you like to make another Volume calculation (1 for Yes, 2 for No)?");
            scanf("%f", &menu1);
            if (menu1 == 2) {
                t = 0;
                break;
            }
            if (menu1 < 1 || menu1 > 2) {
                printf("\n\nUser choice must be between 1 and 2!\n\n");
                printf("Would you like to make another Volume calculation (1 for Yes, 2 for No)?");
                scanf("%f", &menu1);
                if(menu1 == 2) {
                   t = 0;
                   break;
                }
            }
    }
        }

Answer 1

您的 break 语句 [for case 1:] 仅在 if block 中。如果 if 都不是 true，那么您就失败了。

这是你的原作:

case 1:
    // ...
    if (menu1 < 1 || (menu1 > 2) {
        // ...
        if (menu1 == 2) {
            t = 0;
            break;
        }
    }
    // BUG: there should be a break here

case 2:
    // ...
    printf("Enter a and h of the triangular pyramid\n\n");
    printf("a ");
    // ...

固定代码如下:

case 1:
    // ...
    if (menu1 < 1 || (menu1 > 2) {
        // ...
        if (menu1 == 2) {
            t = 0;
            break;
        }
    }
    break;  // FIX: this is your _missing_ break statement

case 2:
    // ...
    printf("Enter a and h of the triangular pyramid\n\n");
    printf("a ");
    // ...