Question

我正在尝试构建一个使用用户输入的小程序，然后使用switch case执行适合用户输入的操作。我一直在努力找到我的计划中的错误，没有运气。显然我缺少一些东西。

这是代码，你能帮我找到它的错误吗？

#include <stdio.h>
#define A 8.5
#define B 7.6
#define C 7.7
#define D 7.7

int main ()
{


    char fuel;
    float amount,total;

    printf("please enter the desired fuel\n");
    scanf_s("%c",&fuel);

   switch(fuel)
   {
   case 'A' :
         printf("how many liters of fuel do you want?\n");
         scanf_s("%f",&amount);
         total=amount*A;
         if(total>150)
         {
             printf("the total price to pay is %.3f: \nYou have won a newspaper", total);
         }
         else
         printf("the total price to pay is %.3f", total);
         break;

      case 'B' :
          printf("how many liters of fuel do you want?\n");
         scanf_s("%f",&amount);
         total=amount*B;
         if(total>150)
             printf("the total price to pay is %f: \nYou have won a newspaper", total);
         else
         printf("the total price to pay is %.3f", total);

          break;
      case 'C' :
         printf("how many liters of fuel do you want?\n");
         scanf_s("%f",&amount);
         total=amount*C;
         if(total>150)
             printf("the total price to pay is %f: \nYou have won a newspaper", total);
         else
         printf("the total price to pay is %.3f", total);
         break;

      case 'D' :
         printf("how many liters of fuel do you want?\n");
         scanf_s("%f",&amount);
         total=amount*D;
         if(total>150)
             printf("the total price to pay is %f: \nYou have won a newspaper", total);
         else
         printf("the total price to pay is %f", total);

      break;

      default: 
      printf("no\n");
      break;
   }



}

即使我输入'A'，'B'，'C'或'D'，它也会变为默认值，而不是适当的情况。谢谢你的帮助。

Answer 1

您没有正确使用scanf_s功能。根据其documentation：

与scanf和wscanf不同，scanf_s和wscanf_s需要缓冲区大小要为c，C，s，S或string类型的所有输入参数指定包含在[]中的控件集。缓冲区大小以字符为单位在指针指向后立即作为附加参数传递缓冲区或变量。

还应该检查错误，所以你应该这样做：

char fuel;
if (scanf_s("%c", &fuel, 1) != 1)  {
    puts("Error from scanf_s");
    return 1;
}

程序跳过开关盒中的所有情况并转到默认值

1 个答案: