Question

我正在尝试编写一个while循环，它仅在用户输入为'F'或'C'时运行。但是，我的while循环似乎不起作用。你能告诉我我的scanf和while循环条件有什么问题吗

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char response;
    while (response == 'F' || response == 'C')
    {
        printf(" Please enter F or C\n");
        scanf(" %c", &response);
    }
    return 0;
}

Answer 1

response未初始化。你的代码还没有进入scanf()。考虑将其更改为do-while循环。

Answer 2

您必须初始化response，试试这个

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

int main()
{
    char response;

    response = 'F';
    while (response == 'F' || response == 'C')
    {
        printf(" Please enter F or C\n");
        scanf(" %c", &response);
    }
    return 0;
}

你当然可以这样做

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

int main()
{
    char response;

    /* since you don't check for `scanf()`'s return value, 
     * this prevents undefined behavior 
     */
    response = 'F';
    do {
        printf(" Please enter F or C\n");
        scanf(" %c", &response);
    } while (response == 'F' || response == 'C');
    return 0;
}

Answer 3

只要response 'F'或'C'，您的循环就会运行。你需要的是

while (response != 'F' && response != 'C')

此外，response未初始化。从

开始

char response = '\0';

Answer 4

在C中有两种常见的输入终止循环方式：

do {
    ...get input...
    do_stuff();
} while (...input does not indicate exit...);

或

while (1) {
    ...get input...
    if (...input indicates exit...) break;

    do_stuff();
}

我认为后者可能更适合您的情况：

while (1) {
    printf(" Please enter F or C\n");
    scanf(" %c", &response);

    if ('F' == response) {
         do_f();
    } else if ('C' == response) {
        do_c();
    } else {
        break;
    }
}

而C编程中的循环条件和终止

4 个答案: