Question

#include <stdio.h>
int main()
{
char cha;
int m=0;
int f=0;
int tot;
while(cha=='m'||cha=='M'||cha=='F'||cha=='f')
{   
    printf("What is your gender?(m or f):\n");      
    scanf(" %c",&cha);
    switch (cha)
    {
        case 'm':
        case 'M':
        printf("\nYou are a male");
        ++m;
        printf("\nPress a to total up");
        break;

        case 'f':
        case 'F':   
        printf("\nYou are a female");
        ++f;
        printf("\nPress a to total up");
        break;

        case 'a':
        tot=m+f;
        printf("\nThe number of male is %d and the number of female is %d",m,f);
        printf("\nThe total of male and female is:%d",tot);
        break;
    }

}

return 0;

}

所以我只是干涉我的代码试图建立一个程序，可以总结在程序中输入的m和f的数量，最终没有输出。程序刚刚终止而没有显示任何输出。我尝试在while表达式的末尾添加分号但是while循环结束甚至不起作用。我的代码出了什么问题？

Answer 1

这个循环表达式：

while(cha=='m'||cha=='M'||cha=='F'||cha=='f')

在 cha通过调用scanf()给出值之前评估。所以基本上你会得到随机行为，因为cha在首次达到该行时未初始化。它保存任何有效字符的可能性非常低，可以立即退出循环。

此外，请注意scanf()可能会失败;你应该经常检查它的返回值。

Answer 2

你不能给一个值。所以它不会进入。我认为这个版本更好。错误处理也很重要。

#include <stdio.h>
int main()
{

char cha;
int m=0;
int f=0;
int tot;
bool end = false;
while(end==false)
{   
    printf("What is your gender?(m or f):\n");      
    scanf(" %c",&cha);

    switch (cha)
    {
        case 'm':
        case 'M':
        printf("\nYou are a male");
        ++m;
        printf("\nPress a to total up");
        break;

        case 'f':
        case 'F':   
        printf("\nYou are a female");
        ++f;
        printf("\nPress a to total up");
        break;

        case 'a':
        tot=m+f;
        end = true;
        printf("\nThe number of male is %d and the number of female is %d",m,f);
        printf("\nThe total of male and female is:%d",tot);
        break;

        default:
        printf("\nEnter valid sex.");
    }

}

return 0;

Answer 3

虽然条件永远不会成真

永远不会成真你应该根据你修改它来工作，虽然我修改了你的代码你可以看看它。

`#include <stdio.h>
 int main()
 {
 char cha;
 int m=0;
 int f=0;
 int tot;
 while(cha!='a')
 {
   printf("What is your gender?(m or f):\n");
   scanf(" %c",&cha);
   switch (cha)
   {
    case 'm':
    case 'M':
    printf("\nYou are a male");
    ++m;
    printf("\nPress a to total up");
    break;

    case 'f':
    case 'F':
    printf("\nYou are a female");
    ++f;
    printf("\nPress a to total up");
    break;

    case 'a':
    tot=m+f;
    printf("\nThe number of male is %d and the number of female is %d",m,f);
    printf("\nThe total of male and female is:%d",tot);
    break;
   }
 }
return 0;
 `}

Answer 4

嗨，你的while循环永远不会满足，因为cha在while循环之前从未初始化。根据您的要求，它应该是do while loop而不是while loop。修改您的代码如下： -

 int main()
 {
   char cha;
   int m=0;
   int f=0;
   int tot;
do
{   
printf("What is your gender?(m or f):\n");      
scanf(" %c",&cha);
switch (cha)
{
    case 'm':
    case 'M':
    printf("\nYou are a male");
    ++m;
    printf("\nPress a to total up");
    break;

    case 'f':
    case 'F':   
    printf("\nYou are a female");
    ++f;
    printf("\nPress a to total up");
    break;

    case 'a':
    tot=m+f;
    printf("\nThe number of male is %d and the number of female is %d",m,f);
    printf("\nThe total of male and female is:%d",tot);
    break;
 }

} while(cha=='m'||cha=='M'||cha=='F'||cha=='f');

return 0;

}

没有带嵌套开关的while循环输出

4 个答案: