用 C 代码创建 GPA 计算器

Question

我刚刚编写了这段代码，但我无法让它工作——更不用说输出所需的结果了。我应该创建一个程序，分别计算未知数量的学生（我已将其缩小到最多 25 个）和未知数量的课程（也将这些学生的 GPA 缩小到最多 10 个，以使我的生活更轻松）。

谁能看到我犯了哪些错误并可能将我推向正确的方向？我感谢任何人的时间和建议:)

我的代码：

// C Program - GPA calculator for x amount of students with x amount of classes
// Program developer: Diana Wright - Novembet 22nd, 2014
#include <stdio.h>

int main(void) {

    // Declare variables
    int grade[5], g, class_num[9], c;
    char name[24], n;
    float GPA=0.0, grade_point=0.0, result=0.0;

    // Input student names implying amount of students
    for(n=0; n<25; n++) {
        scanf(" %s", &name[n]);
        printf("Please enter student names: %s.", name[n]);

        // Input number of classes
        for(c=0; c<10; c++) {
            scanf(" %d", &class_num[c]);
            printf("Please enter amount of classes (max.10): %d", class_num[c]);

            // Input grades
            for(g=0; g<=class_num; g++) {
                scanf(" %d", &grade[g]);    
                printf("Please enter students' grades: %d.", grade[g]);
            }

            // Conversion of grades
            if (grade == "A"){
                grade_point = 4.0;
            }
            if (grade == "B"){
                grade_point = 3.0;
            }
            if (grade == "C")
            {
                grade_point =2.0;
            }
            if (grade == "D"){
                grade_point = 1.0;
            }
            if (grade == "F"){
                grade_point = 0.0;
            }

            // Formula to calculate GPA
            result += grade_point[g];
            GPA = result/class_num[c];
        }
    }

    // Print user input and results in a table
    printf(“\n Student name \t Grades \t GPA”);
    for(n=0; n<25; n++) {
        printf(“ %s \t %d \t %f”, name[n], grade[g], GPA);
    }
    return 0;
}

我的初始输入：

Diana 3 A A A Edward 4 B C B A Stuart 4 A F C D Bert 2 F F

Answer 1

// the following implements the needed data set,
// corrects several coding errors
// has (not yet run) compiling code

编辑：以下代码已过时，请进一步查看新代码

#include <stdio.h>
#include <string.h>

struct studentGrade
{
    char name[24];
    char grades[10];
    int  class_num;
    float GPA;
};


int main(void)
{

    // Declare variables
    struct studentGrade studentGrades[25] = {{"",{'F','F','F','F','F','F','F','F','F','F'},0,0.0F}};


    int  c; // index into student grades[]

    int n; // student number/loop counter


    float grade_point=0.0f, result=0.0f;

    // Input student names implying amount of students
    for(n=0; n< (sizeof( studentGrades)/sizeof(struct studentGrade)); n++)
    {
        result = 0.0f; // initialize for each student

        printf( "please enter student name:\n     ");
        scanf(" %s", (char*)(studentGrades[n].name) );
        printf("Student Name is: %s.", studentGrades[n].name);

        printf("please enter student class count:\n");
        scanf(" %d", &studentGrades[n].class_num);
        printf("Student Number of classes: %d", studentGrades[n].class_num);

        // Input class grades
        for(c=0; c< 10; c++)
        {
            printf("please enter grade for class: %d", c);
            scanf(" %c", &(studentGrades[n].grades[c]));
            printf("student grade for class: %d is %c\n", c, studentGrades[n].grades[c]);


            // following makes wild assumption that grade entered
            // is 'A'...'F'
            // Conversion of grades
            grade_point = 0.0f; // init for each class
            switch( studentGrades[n].grades[c] )
            {
                case 'A':
                    grade_point = 4.0f;
                    break;

                case 'B':
                    grade_point = 3.0f;
                    break;

                case 'C':
                    grade_point = 2.0f;
                    break;

                case 'D':
                    grade_point = 1.0f;
                    break;

                case 'F':
                    grade_point = 0.0f;
                    break;

                default:
                    printf( "invalid grade entered\n");
                    c--; // so will properly handle loop control, etc
                    break;
            }  // end switch
            result += grade_point;


            // Formula to calculate GPA
            result += grade_point;
        } // end for each grade

        studentGrades[n].GPA = result/(float)c;
    } // end for each student

    // Print user input and results in a table
    printf("\n Student name \tGPS\n\t\tgrades\n");

    for(n=0; n< (sizeof(studentGrades) / sizeof( struct studentGrade)); n++)
    {
        if( 0 != strlen(studentGrades[n].name) )
        {
            printf( " %s \tGPS: %.2f\n",
                studentGrades[n].name,
                studentGrades[n].GPA);
            for( c=0; c< studentGrades[n].class_num; c++)
            {
                printf("\tclass: %d\t%c:\n", c, studentGrades[n].grades[c] );
            }
        }
    }
    return 0;
}

编辑：新代码：

1. 干净编译
2. 正确检查错误
3. 使用#define 语句消除“神奇”数字
4. 清理总是尝试输入10个等级的逻辑错误
5. 允许大写和小写成绩输入
6. 使用有意义的变量名
7. 包含适当的水平间距以提高可读性

现在是新代码：

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

#define MAX_STUDENTS 25
#define MAX_NAME_LEN 23
#define MAX_GRADES   10


#define STR_VALUE(x) STR(x)
#define STR(x) #x



struct studentGrade
{
    char name[ MAX_NAME_LEN+1 ];
    char grades[ MAX_GRADES ];
    int  class_num;
    float GPA;
};


int main(void)
{
    // Declare variables
    struct studentGrade studentGrades[ MAX_STUDENTS ] =
    {
        {"",
            {'F','F','F','F','F','F','F','F','F','F'}
            ,0,
            0.0F
        }
    };



    float result      = 0.0f;

    // Input student names implying amount of students
    for( size_t whichStudent=0;
        whichStudent < (sizeof( studentGrades)/sizeof(struct studentGrade));
        whichStudent++)
    {
        result = 0.0f; // initialize for each student

        printf( "please enter student name:\n     ");

        if( scanf(" %" STR_VALUE(MAX_NAME_LEN) "s",
                studentGrades[ whichStudent ].name ) != 1 )
        {
            fprintf( stderr, "scanf for student name failed");
            exit( EXIT_FAILURE );
        }

        // implied else, scanf for student name successful
        printf("Student Name is: %s.",
                studentGrades[ whichStudent ].name);

        printf("please enter student class count:\n");
        if( scanf(" %d", &studentGrades[ whichStudent ].class_num) != 1 )
        {
            fprintf( stderr, "scanf for student class count failed\n" );
            exit( EXIT_FAILURE );
        }

        // implied else, scanf for student class count successful

        printf("Student Number of classes: %d",
            studentGrades[ whichStudent ].class_num);

        // Input class grades
        for( int whichClass=0;
            whichClass < studentGrades[ whichStudent ].class_num;
            whichClass++)
        {
            printf( "please enter grade for class: %d", whichClass );
            if( scanf( " %c",
                        &(studentGrades[ whichStudent ].
                            grades[ whichClass ]) ) != 1)
            {
                fprintf( stderr,
                        "scanf for class grade %d failed\n",
                        whichClass );
                exit( EXIT_FAILURE );
            }

            // implied else, scanf for class grade successful

            printf( "student grade for class: %d is %d\n",
                whichClass,
                studentGrades[ whichStudent ].grades[ whichClass ] );


            // following makes wild assumption that grade entered
            // is 'A'...'F'
            // Conversion of grades
            float grade_point = 0.0f; // init for each class
            switch( studentGrades[ whichStudent ].grades[ whichClass ] )
            {
                case 'A':
                case 'a':
                    grade_point = 4.0f;
                    break;

                case 'B':
                case 'b':
                    grade_point = 3.0f;
                    break;

                case 'C':
                case 'c':
                    grade_point = 2.0f;
                    break;

                case 'D':
                case 'd':
                    grade_point = 1.0f;
                    break;

                case 'F':
                case 'f':
                    grade_point = 0.0f;
                    break;

                default:
                    printf( "invalid grade entered\n");
                    whichClass--; // so will properly handle loop control, etc
                    break;
            }  // end switch
            result += grade_point;


            // Formula to calculate GPA
            result += grade_point;
        } // end for each grade

        studentGrades[ whichStudent ].GPA =
            result/(float)studentGrades[ whichStudent ].class_num;
    } // end for each student

    // Print user input and results in a table
    printf( "\n Student name \tGPS\n\t\tgrades\n" );

    for( size_t whichStudent=0;
         whichStudent < (sizeof(studentGrades) / sizeof( struct studentGrade));
         whichStudent++ )
    {
        if( 0 != strlen( studentGrades[ whichStudent ].name ) )
        {
            printf( " %s \tGPS: %.2f\n",
                studentGrades[ whichStudent ].name,
                studentGrades[ whichStudent ].GPA );

            for( int whichClass=0;
                  whichClass < studentGrades[ whichStudent ].class_num;
                  whichClass++)
            {
                printf( "\tclass: %d\t%c:\n",
                    whichClass,
                    studentGrades[ whichStudent ].grades[ whichClass ] );
            }
        }
    }
    return 0;
}

Answer 2

这东西有点生疏，但我认为这里发生了一些可能不是故意的奇怪事情。

for(g=0; g<=class_num; g++) 

假设我们正在寻找存储在偏移量 c 处的输入值，而不是数组。

for(c=0; c<10; c++)

我不太确定这个循环的价值。我们应该只需要为每个学生获取一次班级数量。

if (grade == "A")

同样，这并没有在数组中获取正确的偏移量。与 char 的比较是否需要单引号？

您还将打印出一堆打印语句...例如，您可能希望将此行移到循环之外：

printf("Please enter students' grades: %d.", grade[g]);

Answer 3

因此，无论这是否是家庭作业，都不要对你的案子提出任何质疑，并赞扬笑松和 Gopi 已经说过的话......

您的代码中有一些明显的错误会阻止您编译和运行以产生任何影响。首先让我们看看你的变量声明：

// Declare variables
// You don't initialize any of your char or int non array and array variables. 
int grade[5], g, class_num[9], c;
char name[24], n;
float GPA=0.0, grade_point=0.0, result=0.0; // You initialize your floating point variables.

当您初始化时，编译器将指定这些变量将驻留的内存区域。如果您不这样做，编译器就会开始对您正在使用的变量进行“假设”，并将随机内存位置分配给您的变量.下一个：

for (c = 0; c<10; c++) {
        scanf(" %d", &class_num[c]); // You ask the user to enter one digit at a time for the class number
        printf("Please enter amount of classes (max.10): %d", class_num[c]); 

        // Input grades
        for (g = 0; g <= class_num; g++) // You try and make a comparison to a single variable int to an entire array which is not allowed.
        {
            scanf(" %d", &grade[g]);
            printf("Please enter students' grades: %d.", grade[g]);
        }

您不能将单个变量与整个数组进行比较，这一行 for (g = 0; g <= class_num; g++) 将无法编译。另一个：

if (grade == "A"){
        grade_point = 4.0;
        }

您尝试将等级（在您的情况下是 int 数据类型）与字符串/字符文字 "A" 进行比较，这是不允许的...

result += grade_point[g]

Grade_point 在这里变成了一个数组，之前没有这样定义过...

这看起来像是您匆忙完成了程序的设计过程。我建议你坐下来，拿着一张纸和一支铅笔/钢笔，写下你在询问用户输入的每个阶段要完成的工作。这将有助于定义您应该使用哪些变量数据类型来完成您的任务。