加法和赋值错误

Question

我的代码有问题。我的程序是一个注册系统，每次我选择一个开关案例，它应该显示总价格，但在选择最后一个主题注册后，总价格添加似乎是错误的。请帮帮忙。

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

int main() 
{
    int n, none, ntwo, nthree, Total;
    float Algebra, Trigonometry, Calculus, Engiana, Physics;
    char password[20], username[8];
    Algebra = 100;
    Trigonometry = 300;
    Calculus = 500;
    Engiana = 750;
    Physics = 1500;
    Total = (none + ntwo + nthree);

    printf("Welcome to the Enrollment System \n");
    printf("Here is the list of Available Subjects \n");
    printf("\n");
    printf("Course Code         Price\n");
    printf("\n");
    printf("1. Algebra             %.2f \n",Algebra);
    printf("2. Trigonometry        %.2f \n",Trigonometry);
    printf("3. Calculus            %.2f \n",Calculus);
    printf("4. Engiana             %.2f \n",Engiana);
    printf("5. Physics             %.2f \n",Physics);

    printf("You can only select three courses to enroll for the Term \n");
    printf("\n Select First Course to Enroll \n");
    scanf("%d", &none);

    switch(none) 
    {
        case 1: printf(" You Enrolled Algebra %.2f \n",Algebra); break; //if conditions met , immediately goes to system pause
        case 2: printf(" You Enrolled Trigonometry %.2f \n", Trigonometry); break; //if conditions not met goes to another case
        case 3: printf(" You Enrolled Calculus %.2f \n", Calculus); break;
        case 4: printf(" You Enrolled Engiana %.2f \n", Engiana); break;
        case 5: printf(" You Enrolled Physics %.2f \n", Physics); break;
        default: printf(" The Course you entered is not valid \n"); break;
    }
    printf("\n Select Second Course to Enroll \n");
    scanf("%d", &ntwo);

    switch(ntwo) 
    {
        case 1: printf(" You Enrolled Algebra %.2f \n",Algebra); break; //if conditions met , immediately goes to system pause
        case 2: printf(" You Enrolled Trigonometry %.2f\n", Trigonometry); break; //if conditions not met goes to another case
        case 3: printf(" You Enrolled Calculus %.2f\n", Calculus); break;
        case 4: printf(" You Enrolled Engiana %.2f\n", Engiana); break;
        case 5: printf(" You Enrolled Physics %.2f \n", Physics); break;
        default: printf(" The Course you entered is not valid \n"); break;
    }

    printf("\n Select Third Course to Enroll \n");
    scanf("%d", &nthree);
    switch(nthree) 
    {
        case 1: printf(" You Enrolled Algebra %.2f \n",Algebra); break; //if conditions met , immediately goes to system pause
        case 2: printf(" You Enrolled Trigonometry %.2f \n", Trigonometry); break; //if conditions not met goes to another case
        case 3: printf(" You Enrolled Calculus %.2f \n", Calculus); break;
        case 4: printf(" You Enrolled Engiana %.2f \n", Engiana); break;
        case 5: printf(" You Enrolled Physics %.2f \n", Physics); break;
        default: printf(" The Course you entered is not valid \n"); break;
    }

    printf("Total Tuition Price = %.2f \n",Total);
    system("PAUSE");
    return 0;
}

Answer 1

Total = (none + ntwo + nthree);

这一行应该排在最后。

也就是说，代码的底部应该如下所示

    Total = (none + ntwo + nthree);
    printf("Total Tuition Price = %.2f \n",Total);
    system("PAUSE");
    return 0;
}

请记住，这些指令是按照它们编写的顺序执行的，在您的原始代码中，Total是在用户有机会回答之前就计算出来的。

顺便说一句，我知道你可能刚刚开始学习，但这是我遵循的一条格言，如果你复制粘贴的代码超过一行，你可以做得更好。一旦您了解了函数、数组和结构，您可能会重新考虑这一点，并尝试减少任何类型的代码重复。

其他两个回答者指出了一个同样有效的问题，您当前只是添加用户输入，并且您可能希望添加成本(?)课程本身。

Answer 2

你有一个逻辑错误。你需要把你的变量Total的赋值语句放在scanf后面。但您必须在switch语句中使用正确的数量更新Total。

示例：

    case 1: printf(" You Enrolled Algebra %.2f \n",Algebra); Total += 100; break; //if conditions met , immediately goes to system pause
     case 2: printf(" You Enrolled Trigonometry %.2f \n", Trigonometry); Total += 300; break; //if conditions not met goes to another case
     case 3: printf(" You Enrolled Calculus %.2f \n", Calculus); Total += 500; break;
     case 4: printf(" You Enrolled Engiana %.2f \n", Engiana);Total += 750; break;
     case 5: printf(" You Enrolled Physics %.2f \n", Physics); Total += 1500; break;
     default: printf(" The Course you entered is not valid \n"); break;
     }
        printf("\n Select Second Course to Enroll \n");
        scanf("%d", &ntwo);`

PS:您的代码可以使用循环进行改进。

Answer 3

主要有两个错误

您的Total变量是int数据类型。所以在打印时，你应该使用%d。要使用%.2f，您应该将Total变量设置为float

为了找到学费总价，你应该在每种情况下添加学费，如下所示

 case 1:Total += Algebra; printf(" You Enrolled Algebra %.2f \n",Algebra); break; //if conditions met , immediately goes to system pause
 case 2:Total += Trigonometry;  printf(" You Enrolled Trigonometry %.2f \n", Trigonometry); break; //if conditions not met goes to another case
 case 3:Total += Calculus;  printf(" You Enrolled Calculus %.2f \n", Calculus); break;
 case 4:Total += Engiana;  printf(" You Enrolled Engiana %.2f \n", Engiana); break;
 case 5:Total += Physics;  printf(" You Enrolled Physics %.2f \n", Physics); break;
 default: printf(" The Course you entered is not valid \n"); break;

另外，您应该用0而不是(none + ntwo + nthree)初始化Total