Question

当我为scanf()

输入值时

它只是在它之后跳过第二个，第三个和任何其他scanf()。

这是我的代码：

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    float manyTest, gr1, gr2, gr3, gr4, gr5, gr6, gr7, gr8;
    manyTest = gr1 = gr2 = gr3 = gr4 = gr5 = gr6 = gr7 = gr8 = 0;

    printf("How many tests you wanna average? (Minimum 1 Maximum 8)\n");
    scanf(" %f", &manyTest);

    if (manyTest <= 0) {
        printf("The Minimum is 1!\n");    
    } else
    if (manyTest > 8) {
        printf("The Maximum is 8!\n");
    } else {
        if (manyTest = 1) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
        } else
        if (manyTest = 2) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
        } else
        if (manyTest = 3) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr3);    
        } else
        if (manyTest = 4) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr2);
            scanf(" %f", &gr3);
            scanf(" %f", &gr4);
        } else
        if (manyTest = 5) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr2);
            scanf(" %f", &gr3);
            scanf(" %f", &gr4);
            scanf(" %f", &gr5);
        } else
        if (manyTest = 6) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr2);
            scanf(" %f", &gr3);
            scanf(" %f", &gr4);
            scanf(" %f", &gr5);
            scanf(" %f", &gr6);
        } else
        if (manyTest = 7) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr2);
            scanf(" %f", &gr3);
            scanf(" %f", &gr4);
            scanf(" %f", &gr5);
            scanf(" %f", &gr6);
            scanf(" %f", &gr7);
        } else
        if (manyTest = 8) {
            printf("Write down your grades on those tests:\n");
            scanf(" %f", &gr1);
            scanf(" %f", &gr2);
            scanf(" %f", &gr2);
            scanf(" %f", &gr4);
            scanf(" %f", &gr5);
            scanf(" %f", &gr6);
            scanf(" %f", &gr7);
            scanf(" %f", &gr8);
        }
        float avg = (gr1 + gr2 + gr3 + gr4 + gr5 + gr6 + gr7 + gr8) / manyTest;
        printf("Your average grade is: %.2f\n", avg);
    }
    system("pause");
    return 0;
}

我的代码有什么问题导致它跳过scanf()的其余部分？我想让代码做的是询问他们想要平均多少次测试，然后取这个数字（在1到8之间）并进行测试，然后它应该平均成绩。

让我们说：

How many test...?
2
Write down your grades:
100
90
Your average grade is: 95.00

但它真正做的是：

How many test.....?
2
Write down your grades:
90
Your average is: 90.00

并且甚至不让它获取其他变量的信息。

Answer 1

实际上，在您的代码中，罪魁祸首不是scanf，而是wrong个等式

else if (manyTest = 8) //WROOOOONNGGGG!! =( =( =( =(

改为双等号......

else if (manyTest == 8) //correct! =)

因为你真正想要的是比较

Answer 2

问题是以下语句将始终与第一个if。匹配。

首先，您需要使用==进行比较，因为使用=只会使这成为一项任务。

其次，赋值manyTest = 1将始终评估为true，因为它是如何工作的。因此，当您到达if (manyTest = 1)时，条件将为真，因此您将输入第一个只有一个scanf的情况。你永远不会到达其他if语句并测试这些条件。

if (manyTest = 1) {
    printf("Write down your grades on those tests:\n");
    scanf(" %f", &gr1);
}
else if (manyTest = 2) {
    printf("Write down your grades on those tests:\n");
    scanf(" %f", &gr1);
    scanf(" %f", &gr2);
}
...

将来调试时你可以在每个if语句中使用printf中的不同文本来更好地理解出错的地方。

Answer 3

您的代码中存在一个经典错误：

您在测试中使用赋值运算符=而不是比较运算符==。 C非常灵活：它允许在测试表达式中进行分配，这会导致您遇到的经典错误。你被咬了一次，所以现在你知道你应该键入什么。任何人都可以打错，有一种非常有效的方法来防止这个问题：编译并启用警告（例如：gcc -Wall -Wextra -Werror）。

使用多个scanf（）时，它会跳过scanf的其余部分（）

3 个答案: