为什么我总是收到无效的反馈？

Question

过去 36 小时我一直在研究 cs50 pset1 学分。我的代码没有产生任何错误，但是当我输入我的银行卡详细信息时，它显示无效，这可能是什么问题。我是菜鸟，请大家帮忙

#include <stdio.h>
#include <cs50.h>

 int main (void)
{
    long long ccnumber;

     do 
     {
         //Prompting the user for his creditcard number
         ccnumber=get_long_long("What is your creditcard number\n");
     }
     while (ccnumber<= 0);

     //validating the credit card number to ascertain if its upto 13. 14 or 16
    long long numbers = ccnumber;
     int totaldigits = 0; 

     while (numbers > 0)
     {
         numbers = numbers/10;
         totaldigits++;
     }
     if(totaldigits != 13 || totaldigits !=14 || totaldigits !=16)
     {
         printf("Invalid\n");
     }

     //Starting from the second to last digit
     //And multiplying through by 2
     int number1 = ((ccnumber/10) % 10) *2;
     int number2 = ((ccnumber/1000) % 10) *2;
     int number3 = ((ccnumber/100000) % 10) *2;
     int number4 = ((ccnumber/10000000) % 10) *2;
     int number5 = ((ccnumber/1000000000) % 10) *2;
     int number6 = ((ccnumber/100000000000) % 10) *2;
     int number7 = ((ccnumber/10000000000000) % 10) *2;
     int number8 = ((ccnumber/10000000000000000) % 10) *2;

     //Getting the Sum of the first number series
     int sum1;
         sum1 = (number1 + number2 + number3 + number4 + number5 + number6 + number7 + number8);

     //Populating the second number series
     int number9 = ccnumber % 10;
     int number10 = ((ccnumber/100) % 10);
     int number11 = ((ccnumber/10000) % 10);
     int number12 = ((ccnumber/1000000) % 10);
     int number13 = ((ccnumber/100000000) % 10);
     int number14 = ((ccnumber/10000000000) % 10);
     int number15 = ((ccnumber/1000000000000) % 10);
     int number16 = ((ccnumber/100000000000000) % 10);

    int sum2;
        sum2 =(number9 + number10 + number11 + number12 + number13 + number14 + number15 + number16);

     //Adding sum1 and sum2
     int checksum;
         checksum = sum1 + sum2;
     if (checksum % 10 != 0)
     {
         printf("invalid/n");
      }

     //Verifying for visacard(1)
     if(totaldigits == 13)
     {
         printf("Visa\n");
     }

     // Verifying for visa(2)
     if(totaldigits == 16)
     {
         long long visa;
         visa = ccnumber/1000000000000000;
       if(visa!=4)
       {
           printf("Invalid\n");
       } 
         else 
         {
             printf("VISA\n");
         }
         //Verifying for MasterCard
         long long master;
         master = ccnumber/100000000000000;
         if(master!=51 || master!=52 ||master!=53 ||master!=54 ||master!=55)
         {
             printf("Invalid\n");
         }
         else
         {
             printf("MASTER\n");
         }
     }

       //Verifying for Amex
     }

/柜台您的信用卡号码是多少 2221000000000009 无效的 invalid/nInvalid 无效

Answer 1

首先，你的某些if条件是错误的。例如，

if(totaldigits != 13 || totaldigits != 14 || totaldigits != 16)

你想检查totaldigits是13还是14还是16，但是你这里检查的是如果totaldigits不是13，则打印invalid或如果 totaldigits 不是 14，则打印 invalid 等等。因此，它总是打印无效。您需要使用 && (AND) 而不是 || (OR)。

这一行也存在同样的问题

if(master!=51 || master!=52 ||master!=53 ||master!=54 ||master!=55)

另一个问题是你把1个不必要的0放在这一行的除法中，所以它总是产生0。

int number8 = ((ccnumber/10000000000000000) % 10) *2; // 1 zero unnecessary

正如评论中所建议的那样，您可能需要考虑创建一个数组来存储单个数字，而不是使用 16 个不同的整数。当你有一个数组时，你可以在 for 循环中进行除法，这样你就不会与很多零混淆。作为例子，你可以参考这个 link A solution for cs50's credit card validation problem .

为什么我总是收到无效的反馈？

Why do i keep getting an invalid feedback?

c

credits

cs50