程序，不返回任何东西

Question

我正在C程序工作，可以返回贷款支付。 yearInt是一年利息 loanAmt是贷款 总量monthlyPay是按月支付 numberPay每月支付

对于一些原因的号码，当我运行该程序，就什么也不显示，即使我在一个负型数。

有没有办法解决它？

#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

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

在这两个错误的参数传递给%f，因此，导致UB。使用%d说明符。

而在这其中}缺失 -

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 
} 

else {前放一个}。

Answer 2

您使用了错误的格式说明阅读loanAmount和numberPay。而不是"%f"，请使用"%d"。

scanf("%d", &loanAmt); 

和

scanf("%d", &numberPay); 

此外，经常检查scanf返回值，以确保它能够将数据分配给所有的变量。

改变循环：

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); 
    } 
} 

这将是最好还是把所有的检查，在功能和main调用该函数。

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: "); 

加入类似的功能来读取float S和调用它的读取是float类型的变量。