C编程：通过循环运行程序？

Question

我正在尝试编写一个程序来计算您的更改并报告总金额。我能够编写函数来计算变化，但我不确定如何让它在循环中运行。另一件事是，当程序询问他们的姓名时，我希望用户按 Enter 或返回退出，但我也不确定如何。这是我的第一堂编程课，我正在努力变得更好。感谢您的宝贵时间。

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <time.h>

float countChange(int quarters, int dimes, int nickles, int pennies);

int main(void) 
{
  int a,b,c,d;
  char yourname[20];
  printf("Your total money is $ %0.2f \n", countChange(12,23,34,45));
  printf("What is your name (Return/Enter to quit)?");
  scanf("%s", yourname);
  printf("\nHow many quarters do you have? \n" );
  scanf("%d", &a);
  printf("\nHow many dimes do you have? \n" );
  scanf("%d", &b);
  printf("\nHow many nickles do you have? \n" );
  scanf("%d", &c);
  printf("\nHow many pennies do you have? \n" );
  scanf("%d", &d);
  printf("All counted, %s has $ %0.2f\n", yourname, countChange(a,b,c,d));
  return 0;
}

float countChange(int quarters, int dimes, int nickles, int pennies)
{
  float QuartersTotal, DimesTotal, NicklesTotal, PenniesTotal, total;
  QuartersTotal= quarters*0.25;
  DimesTotal= dimes*0.10;
  NicklesTotal= nickles*0.05;
  PenniesTotal= pennies*0.01;
  total= QuartersTotal+ DimesTotal+ NicklesTotal+ PenniesTotal;
  return total;
}

Answer 1

我建议你应该使用 fgets 而不是 scanf 来读取任意长度的字符串，这样更安全。 （避免溢出）

while (1)
{
    printf("Your total money is $ %0.2f \n", countChange(12, 23, 34, 45));
    printf("What is your name (Return/Enter to quit)?");

    fgets(yourname, sizeof(yourname), stdin);

    if (yourname[0] == '\n')
        break;

    printf("\nHow many quarters do you have? \n");
    scanf("%d", &a);
    printf("\nHow many dimes do you have? \n");
    scanf("%d", &b);
    printf("\nHow many nickles do you have? \n");
    scanf("%d", &c);
    printf("\nHow many pennies do you have? \n");
    scanf("%d", &d);
    printf("All counted, %s has $ %0.2f\n", yourname, countChange(a, b, c, d));
    getchar();
}

Answer 2

如果您希望程序不断询问用户，您可以简单地使用：

FILE
getline
scanf OR fscanf ...

得到它。

例如，

FILE * prompt = stdin;
int result = 0;
while ((int)(result = getline(&line, &capacity, prompt)) != -1) {Your code here}

这段代码的本质是：

1.从标准输入读取

2。从输入中读取该行，直到它被告知停止

此代码将永远运行，除非用户想要退出或程序退出。 当给定 command + D 或 command + C 时，它会退出，这是 kill 命令。

Answer 3

我清理了代码并添加到循环中，希望对您有所帮助：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

float countChange(int quarters, int dimes, int nickles, int pennies)
{
    float QuartersTotal, DimesTotal, NicklesTotal, PenniesTotal, total;

    QuartersTotal= quarters*0.25;
    DimesTotal= dimes*0.10;
    NicklesTotal= nickles*0.05;
    PenniesTotal= pennies*0.01;
    total= QuartersTotal + DimesTotal + NicklesTotal + PenniesTotal;

    return total;
}

void getNumCoins(char *coinType, int *out)
{
    printf("\nHow many %s do you have?\n", coinType);
    if (scanf("%d", out) <= 0) {
        printf("Please enter a valid integer\n");
        exit(EXIT_FAILURE);
    }
}

int main(void) 
{
    int a,b,c,d;
    char yourname[20];

    while(1)
    {
        printf("Your total money is $ %0.2f \n", countChange(12,23,34,45));
        printf("What is your name (Return/Enter to quit)?");
        scanf("%s", yourname);

        if (yourname[0] == '\n') break;

        getNumCoins("quarters", &a);
        getNumCoins("dimes", &b);
        getNumCoins("nickels", &c);
        getNumCoins("pennies", &d);

        printf("All counted, %s has $ %0.2f\n", yourname, countChange(a,b,c,d));
    }
    return 0;
}

如果您明确想要一个循环，我也可以编辑我的答案以显示这一点，但在您的情况下，我认为它不会让它变得更干净。

希望这会有所帮助！