如何停止无限循环？

Question

我正在编写一个程序，该程序将计算三角形或正方形的面积，然后提示用户是否希望计算另一个。我的代码已经运行到可以计算任一形状的面积的程度，但随后不再继续执行代码的其余部分。例如，如果选择了正方形，则计算面积，然后返回到正方形边长的提示。我假设这又是 while 永远循环，但不知道如何阻止循环无限进行。

这是我的代码：

 #include<stdio.h>
 #include<math.h>
 
 int main(void)
 
 {
     float sq_side, tri_base, tri_height, Area;
     char shape, cont = 'Y';
     
     printf("Please select the type of shape you desire to calculate the area for:\n");
     printf("                                                                     \n");
     printf("   Square = S                             Triangle = T               \n");
     printf("   -------                                    x                      \n");
     printf("   :     :                                   x x                     \n");
     printf("   :     :                                  x   x                    \n");
     printf("   -------                                 xxxxxxx                   \n");
     printf("                                                                     \n");
     printf("Please select either S or T:");
     scanf("%c", &shape);
     while (cont != 'n' && cont != 'N')
     
        if (shape == 'S' || shape == 's')
        {
            printf("What is the length of the sides of the square?:\n");
            scanf("%f", &sq_side);
         
            Area = pow(sq_side,2);
         
            printf("The area of the square is %.2f.\n", Area);
        }   
         
        else if (shape == 'T' || shape == 't')
        {
            printf("What is the length of the base of the triangle?:\n");
            scanf("%f", &tri_base);
            printf("What is the height of the triangle?:\n");
            scanf("%f", &tri_height);
            
            Area = 0.5 * tri_base * tri_height;
            
            printf("The area of the triangle is %.2f.\n", Area);
        }   
        
        else 
        {
        printf("Error:  You have select an incorrect option.");
        }
        
        printf("Do you wish to calculate a new shape?");
        fflush(stdin);
        scanf("%c", &cont);
        
     return(0);
     
 }
 

Answer 1

你缺少大括号。结果是只有 if 语句（包括 else if 链）实际上位于循环体中。 printf（及更高版本）不是此复合语句的一部分。

 while (cont != 'n' && cont != 'N')
 {
    if (shape == 'S' || shape == 's')
    {
        printf("What is the length of the sides of the square?:\n");
        scanf("%f", &sq_side);

        Area = pow(sq_side,2);

        printf("The area of the square is %.2f.\n", Area);
    }   

    else if (shape == 'T' || shape == 't')
    {
        printf("What is the length of the base of the triangle?:\n");
        scanf("%f", &tri_base);
        printf("What is the height of the triangle?:\n");
        scanf("%f", &tri_height);

        Area = 0.5 * tri_base * tri_height;

        printf("The area of the triangle is %.2f.\n", Area);
    }   

    else 
    {
    printf("Error:  You have select an incorrect option.");
    }

    printf("Do you wish to calculate a new shape?");
    fflush(stdin);
    scanf("%c", &cont);
}   

Answer 2

while 循环没有括号。因此 if elseif else 块之外的代码不会被调用。

目前，您的代码将转换为

while (cont != 'n' && cont != 'N')
{
    if (shape == 'S' || shape == 's')
    {}
    else if (shape == 'T' || shape == 't')
    {}   
    else 
    {}
}

printf("Do you wish to calculate a new shape?");
fflush(stdin);
scanf("%c", &cont);

您想要的时间

while (cont != 'n' && cont != 'N')
{
    if (shape == 'S' || shape == 's')
    {}
    else if (shape == 'T' || shape == 't')
    {}   
    else 
    {}

    printf("Do you wish to calculate a new shape?");
    fflush(stdin);
    scanf("%c", &cont);
}

请记住，如果您在控制结构中不包含花括号，它只会调用下一条语句，在您的情况下，它是一系列嵌套的 if-else if 语句。

希望有帮助 - 瓦尔