Question

我正在制作一个可以退还贷款的C程序。 yearInt是年利息 loanAmt是贷款总额 monthlyPay是每月付款 numberPay是每月付款的数量

由于某些原因，当我运行程序时，没有任何显示，即使我输入负数。

无论如何要解决它？

#include <stdio.h>
int main(void)
{
float yearInt = -1;
int loanAmt = -1;
float monthlyPay = -1;
int numberPay = -1;
int count = 0;

while (loanAmt<0)
{
    printf("Please enter valid loan value: \n");
    scanf("%f", &loanAmt);
}

while (yearInt<0)
{
    printf("Please enter valid yearly interest value: \n");
    scanf("%f", &yearInt)
}

while (monthlyPay<0)
{
    printf("Please enter valid monthly payment value: \n");
    scanf("%f", &monthlyPay);
}

while (numberPay<0)
{
    printf("Please enter valid number of monthly payments: \n");
    scanf("%f", &numberPay);
}

if(loanAmt>monthlyPay)
{
    while(count<numberPay)
    {
        loanAmt = loanAmt*(1 + (yearInt/12)) - monthlyPay;
        count += count+1;
    }
    printf("The amount of last payment is: %.2f\n", loanAmt);
else
    printf("The amount of last payment is: %.2f\n", loanAmt);
}
return 0;
}

Answer 1

您使用错误的格式说明符来阅读loanAmount和numberPay。而不是"%f"，请使用"%d"。

scanf("%d", &loanAmt);

和

scanf("%d", &numberPay);

另外，请务必检查scanf的返回值，以确保它能够为所有变量分配数据。

更改循环：

while (loanAmt<0)
{
   printf("Please enter valid loan value: \n");
   scanf("%d", &loanAmt);
}

到

while (loanAmt<0)
{
   printf("Please enter valid loan value: \n");
   if ( scanf("%d", &loanAmt) != 1 )
   {
      // Discard the rest of the line.
      int c;
      while ( (c = fgetc(stdin)) = '\n' && c != EOF );
   }
}

将所有检查放入函数并从main调用函数仍然会更好。

int readInt(char const* prompt)
{
   int val = -1;

   printf("%s\n", prompt);
   while ( scanf("%f", &val) != 1 || val < 0)
   {
      // Discard rest of the line.
      int c;
      while ( (c = fgetc(stdin)) = '\n' && c != EOF );

      // If EOF is reached, we have a problem.
      if ( c == EOF )
      {
         exit(0);
      }
      printf("%s\n", prompt);
   }

   return val;
}

然后，使用：

loanAmount = readInt("Please enter valid loan value: ");

添加一个类似的函数来读取float并调用它来读取float类型的变量。

Answer 2

 scanf("%f", &loanAmt);         // loanAmt is int
 ... 
 scanf("%f", &numberPay);       //numberPay is int

在两个错误的参数中传递给%f，因此导致UB。使用%d说明符。

在这一个}中缺失了 -

if(loanAmt>monthlyPay)
{
   while(count<numberPay)
   {
     loanAmt = loanAmt*(1 + (yearInt/12)) - monthlyPay;
     count += count+1;
   }
   printf("The amount of last payment is: %.2f\n", loanAmt);    //use %d 
     // ADD '}' here 
else    // ADD '{' here 
   printf("The amount of last payment is: %.2f\n", loanAmt);    //use %d 
}

在}之前加else {。

不返回任何内容的程序

2 个答案: