Question

我似乎无法留在while循环中。我输入了ID代码和第一次购买或销售的号码，即使我要求它只在代码输入-1时才会退出。这里有什么简单需要纠正的，还是这个太广泛了？

#include <stdio.h>

int main () {

    int inv1, inv2, inv3, inv4, amount, code;

    printf ("Beer brand IDs \n");
    printf ("1. Piels \n");
    printf ("2. Coors \n");
    printf ("3. Bud \n");
    printf ("4. Iron City \n");

    printf ("Inventory at beginning of week \n");

    printf ("1. Piels:  ");
    scanf ("%d", &inv1);
    printf ("2. Coors:  ");
    scanf ("%d", &inv2);
    printf ("3. Bud:  ");
    scanf ("%d", &inv3);
    printf ("4. Iron City:  ");
    scanf ("%d", &inv4);

    while (code != -1) {
        printf ("ID:  ");
        scanf ("%d", &code);
        printf ("amount requested or subtracted:  ");
        scanf ("%d", &amount);

        if (code == 1) {
            inv1 = inv1 + amount;
        }
        else if (code == 2) {
            inv2 = inv2 + amount;
        }
        else if (code == 3) {
            inv3 = inv3 + amount;
        }
        else if (code == 4) {
            inv4 = inv4 + amount;
        }
        else (code == -1); {
            break;
            }
            printf ("End of week for Piels:  %d", inv1);
            printf ("End of week for Coors:  %d", inv2);
            printf ("End of week for Bud:  %d", inv3);
            printf ("End of week for Iron City: %d", inv4);
    }

    return (0);
}

Answer 1

您的代码存在许多技术逻辑问题。进入循环时，使用 未初始化 时，首先使用code。您的编译器应该警告您有关该问题。确保每次编译时都有 警告启用 （例如-Wall -Wextra），并且不接受编译警告的代码。（您还可以添加-pedantic以查看其他警告）

你有一个乱码else。 else (code == -1);不正确。您似乎打算else { code = 1; break; }。请注意，根本不需要code变量。只需使用while (1)或for (;;)循环，直到break退出循环。

您的提示说subtracted，但您要在代码中添加（例如inv4 = inv4 + amount;）。只需使用-=运算符为每个amount实际减去ID。

始终，请务必检查每次return来电的scanf。这是您验证的唯一方法，您从用户那里收到实际值，并且不会尝试从该点开始处理垃圾（如果您的用户输入小数以外的其他内容

最后，您的"End of week" printf语句应该 在之外循环，而不是在其中。以下是您希望使用代码显示的内容的简短示例：

#include <stdio.h>

int main (void) {

    int inv1, inv2, inv3, inv4;
    inv1 = inv2 = inv3 = inv4 = 0;  /* initialize values */

    printf ("Beer brand IDs \n");
    printf ("1. Piels\n2. Coors\n3. Bud\n4. Iron City\n\n");

    printf ("Inventory at beginning of week\n");

    printf ("1. Piels    :  ");
    if (scanf ("%d", &inv1) != 1) {
        fprintf (stderr, "error: invalid input.\n");
        return 1;
    }
    printf ("2. Coors    :  ");
    if (scanf ("%d", &inv2) != 1) {
        fprintf (stderr, "error: invalid input.\n");
        return 1;
    }
    printf ("3. Bud      :  ");
    if (scanf ("%d", &inv3) != 1) {
        fprintf (stderr, "error: invalid input.\n");
        return 1;
    }
    printf ("4. Iron City:  ");
    if (scanf ("%d", &inv4) != 1) {
        fprintf (stderr, "error: invalid input.\n");
        return 1;
    }

    while (1) {
        int amount = 0, code = 0;
        printf ("ID ('q' to quit):  ");
        if (scanf ("%d", &code) != 1) break;
        printf ("amount requested or subtracted:  ");
        if (scanf ("%d", &amount) != 1) break;

        if (code == 1)
            inv1 -= amount;
        else if (code == 2)
            inv2 -= amount;
        else if (code == 3)
            inv3 -= amount;
        else if (code == 4)
            inv4 -= amount;
        else
            fprintf (stderr, "warning: ID out of range.\n");
    }

    printf ("\nEnd of week for Piels     :  %d\n", inv1);
    printf ("End of week for Coors     :  %d\n", inv2);
    printf ("End of week for Bud       :  %d\n", inv3);
    printf ("End of week for Iron City :  %d\n", inv4);

    return (0);
}

示例使用/输出

$ ./bin/rfmt
Beer brand IDs
1. Piels
2. Coors
3. Bud
4. Iron City

Inventory at beginning of week
1. Piels    :  10
2. Coors    :  10
3. Bud      :  10
4. Iron City:  10
ID ('q' to quit):  1
amount requested or subtracted:  2
ID ('q' to quit):  2
amount requested or subtracted:  3
ID ('q' to quit):  3
amount requested or subtracted:  4
ID ('q' to quit):  4
amount requested or subtracted:  5
ID ('q' to quit):  q

End of week for Piels     :  8
End of week for Coors     :  7
End of week for Bud       :  6
End of week for Iron City :  5

仔细看看，如果您有其他问题，请告诉我。

库存C程序，啤酒库存循环

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