Question

在过去的3天里，我一直在尝试修复此代码。有人可以帮忙。如果插入负数，程序不会打印最后一个语句。如果输入负数，而不是打印“终止程序...”，它会在退出之前跳转到打印“输入第一个数字：”。

int main(void)
{
    int choose, number1, number2, total_hold;
    do
    {
        printf("\n");
        printf("1: sum of two numbers \n");
        printf("2: difference of two numbers\n");
        printf("3: product of two numbers\n");
        printf("<0:terminate the program\n");
        printf("Select calculation:");
        scanf("%d", &choose);

        printf("Enter the first number:");
        scanf("%d", &number1);

        printf("Enter the second number:");
        scanf("%d", &number2);

        if (choose == 1)
        {
            total_hold = sumOfNumbers(number1, number2);
            displayS(number1, number2, total_hold);
        }
        else if (choose == 2)
        {
            total_hold = differenceOfNumbers(number1, number2);
            displayD(number1, number2, total_hold);
        }

        else if (choose == 3)
        {
            total_hold = MultiplicationOfNumbers(number1, number2);
            displayM(number1, number2, total_hold);
        }
        else if (choose < 0)
        {
            printf("Terminating the program...");
            break;
        }

    }
    while (choose > 0);

    return 0;
}

Answer 1

放置这个：

if (choose < 0)
{
    printf("Terminating the program...");
    break;
}

紧接着scanf("%d", &choose)。

除此之外，您也可以将while (choose > 0)更改为while (1)。

Answer 2

您正在使用

do{
statement 1;
statement 2;
...
...
statement n;
}while(condition);

因此，在do-while循环中，所有语句至少执行一次，然后检查条件。

最好使用while循环而不是do-while

Answer 3

您在任何if语句之前执行三条scanf指令。如果你想检查选择变量是否低于0你可以在其他两个scanf调用之前执行此操作

int main(void)
{
    int choose, number1, number2, total_hold;
    do
    {
        printf("\n");
        printf("1: sum of two numbers \n");
        printf("2: difference of two numbers\n");
        printf("3: product of two numbers\n");
        printf("<0:terminate the program\n");
        printf("Select calculation:");
        scanf("%d", &choose);

        if (choose < 0)
        {
            printf("Terminating the program...");
            break;
        }

        printf("Enter the first number:");
        scanf("%d", &number1);

        printf("Enter the second number:");
        scanf("%d", &number2);

        if (choose == 1)
        {
            total_hold = sumOfNumbers(number1, number2);
            displayS(number1, number2, total_hold);
        }
        else if (choose == 2)
        {
            total_hold = differenceOfNumbers(number1, number2);
            displayD(number1, number2, total_hold);
        }

        else if (choose == 3)
        {
            total_hold = MultiplicationOfNumbers(number1, number2);
            displayM(number1, number2, total_hold);
        }

    }
    while (choose > 0);

    return 0;
}

Answer 4

言

printf("Enter the first number:");
scanf("%d", &number1);

printf("Enter the second number:");
scanf("%d", &number2);

独立于可变choose中输入的值执行，因为在这些语句之后对最后一个进行了测试。

程序的设计更正确（没有测试）

#include <stdio.h>

int main(void)
{
    while ( 1 )
    {
        enum { Exit = 0, Addition = 1, Difference = 2, Multiplication = 3 };

        unsigned int choose;
        int number1, number2, total_hold;

        printf( "\n" );
        printf( "%d: sum of two numbers \n", Addition );
        printf( "%d: difference of two numbers\n", Difference );
        printf( "%d: product of two numbers\n", Multiplication );
        printf( "%d: terminate the program\n", Exit );
        printf( "Select calculation:" );

        scanf( "%u", &choose );

        if ( choose == Exit )
        {
            printf( "Terminating the program..." );
            break;
        }

        if ( choose <= Multiplication )
        { 
            printf( "Enter the first number:" );
            scanf( "%d", &number1 );

            printf( "Enter the second number:" );
            scanf( "%d", &number2 );
        }

        switch ( choose )
        {
        case Addition:        {
            total_hold = sumOfNumbers(number1, number2);
            displayS(number1, number2, total_hold);
            break;

        case Difference:
            total_hold = differenceOfNumbers(number1, number2);
            displayD(number1, number2, total_hold);
            break;

        case Multiplication:
            total_hold = MultiplicationOfNumbers(number1, number2);
            displayM(number1, number2, total_hold);
            break;

        default:
            printf("Invalid selection. Try again.\n");
            break;
        }
    }

    return 0;
}

如果while循环中的语句不起作用

4 个答案: