为什么我的代码返回错误的值？

debugcn 发表于 Dev

用户名

我是C语言的新手，我想弄清楚为什么我的代码返回错误的值。

int main()
{


    printf("Welcome to my number generator! \n");
    printf("What is the first number in the range? \n");
    int rng1 = scanf("%d", &rng1);
    printf("What is the second number in the range? \n");
    int rng2 = scanf("%d", &rng2);
    printf("What would increment would you like to go up in? \n");
    int inc = scanf("%d", &inc);

    do
        {
        printf("%d\n"rng1);
        rng1 += inc;
        }
    while(rng1 != rng2);
    }
    return 0;
    }

从此代码中，我期望第一个范围和第二个范围之间的数字列表以某个数字递增，但是我得到的值为1。我在做什么错呢？PS我试图对其进行“调试”，发现使用以下命令时：

if(isalpha(rng1));
    printf("I am a String...")
if(isdigit(rng1))
    printf("I am a Digit")

它返回“我是弦乐...”。

谢谢！

海

您已经为变量分配了输入值rng1，rng2并inc通过调用scanf和还scanf成功填充了参数列表的项数。因此，将的返回值分配scanf给这些变量是不正确的。只需将返回值用作输入数量即可。您应该读取值1，因为您只希望读取一个值scanf。此外，您还可以检查输入值，以检测输入的值是否有效。

除此之外，我想对您的代码进行一些修改。特别是do{...}while();由于!=操作员，您的循环可能会无限期地运行。请在下面的代码中查看注释。

int main()
{
    /* Declare the variables and do not assign the return value of scanf */
    int rng1, rng2, inc;
    printf("Welcome to my number generator! \n");
    printf("What is the first number in the range? \n");
    /* repeat this check condition for each scanf, exit( EXIT_FAILURE ) requires #include <stdlib.h>*/

    if (1 != scanf("%d", &rng1)) {
        exit( EXIT_FAILURE );
    }
    printf("What is the second number in the range? \n");
    scanf("%d", &rng2);
    printf("What would increment would you like to go up in? \n");
    scanf("%d", &inc);

    do
    {
        printf("%d\n",rng1);
        rng1 += inc;
    }
    /* Use <= instead of != and think about the case for rng1 is 1 rng2 is 5 and inc is 3, can you detect the end of the loop by adding 3 to the starting point 1 ? */
    while(rng1 <= rng2);

    /* Remove the `}` here */
    return 0;
}

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