c - 不允许我在我的信息系统项目中输入学生的特定成绩

Question

我的代码要求我输入 .txt 文件中的名称，如果名称有效，我就可以登录。

当程序启动时，用户应该看到三个选项； 按 0 退出 按 1 获取作者信息 按 2 登录 选择 0 退出程序 选择 1 打印您的姓名和学生 ID 选择 3 提示用户输入用户名和密码。 然后，您应该打开文件“passwords”并查看用户是否有权使用该程序*

到目前为止我已经做到了这一点。成功登录后，我可以按选项 2 添加新学生。到目前为止我已经做到了。现在我在选项 4 上犯了一个错误。选项 4 要求我输入学生的成绩。点击选项 4 后，它会询问我的成绩，每当我输入成绩时，程序就会崩溃。我不确定我的错误是什么。

//This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Constants used in the application */
const char * PASSWORD_FILE = "passwords.txt";
const int MAX_STUDENTS = 1000;
const int MAX_GRADES = 100;
const int MAX_CHARS = 25;

//Function to print Author Info
void printAuthorInfo();

//Function to display initial Menu and Get the User's Selection
int showMainMenu();

//Function to Login to the System
int login();

//member menu
int memberMenu();

//Enter GPA for current Student
void enterGPA(char ids[1000][25], float grades[1000][100], int[], int);

//Display student records to stdout
void print(char[1000][25], char[1000][25], char[1000][25], float[1000][100],     
int[], int);

//Save Records to File
void save(char[1000][25], char[1000][25], char[1000][25], float[1000][100],     
int[], int);

//Load Records from File
void load(char fn[1000][25], char ln[1000][25], char ids[1000][25], float   
grades[1000][100], int counts[], int num);

int main()
{
    int loggedIn = 0;
    int choice, subChoice;
    char firstNames[1000][25];
    char lastNames[1000][25];
    char ids[1000][25];
    float grades[1000][100];
    int numGrades[1000];
    char fn[25];
    char ln[25];
    int numStudents = 0;

    //Top Level Loop
    do {
        //display menu and get the user's selection
        choice = showMainMenu();

        if (choice == 0)
        {
            printf("Thank you for using our Application! GoodBy!");
        }
        else if (choice == 1)
        {
            printAuthorInfo();
        }
        else if (choice == 2)
        {
            loggedIn = login();

            if (loggedIn == 1)
            {
                printf("Welcome! You are now Logged In\n");

                //Interact with the user
                do
                {
                    subChoice = memberMenu();

                    if (subChoice == 1)
                    {
                        printAuthorInfo();
                    }
                    else if (subChoice == 2)
                    {
                        printf("Enter First Name: ");
                        scanf("%s", firstNames[numStudents]);
                        printf("Enter Last Name: ");
                        scanf("%s", lastNames[numStudents]);
                        printf("Enter Student ID: ");
                        scanf("%s", ids[numStudents]);
                        numStudents++;
                        printf("Student Has been added to System");
                    }
                    else if (subChoice == 3)
                    {
                        enterGPA(ids, grades, numGrades, numStudents);
                    }
                    else if (subChoice == 4)
                    {
                        print(firstNames, lastNames, ids, grades, numGrades, 
    numStudents);
                    }
                    else if (subChoice == 5)
                    {
                        void save(firstNames, lastNames, ids, grades, counts, 
    numStudents);
                    }
                    else if (subChoice == 6)
                    {
                        load(firstNames, lastNames, ids, grades, numGrades, 
    &numStudents);
                    }
                    else if (subChoice == 7)
                    {
                        printf("\nYou are logged Out Now");
                    }
                    printf("\n");
                } while (subChoice != 7);
            }
            else
            {
                printf("Login Failed - Try again");
            }
        }
        printf("\n\n");
    } while (choice != 0);


    system("pause");
    return 0;
}

void printAuthorInfo()
{
     printf("Author Information\n");
     printf("Author Name: %s\n", "myinfo ");
     printf("Student ID: %s\n", "12345");
}

int showMainMenu()
{
    //User Selection
    int choice;

    do
    {
        //Display menu
        printf("Press 0 to exit\n");
        printf("Press 1 for Author Info\n");
        printf("Press 2 for Login\n");
        printf("Enter choice? ");

        //Read the selection
        scanf("%d", &choice);
        printf("\n");
    } while (choice < 0 || choice > 2);

   //Return selection
   return choice;
}

int login()
{
    //Get User's username and password
    char username[30];
    char password[30];
    char usernameInFile[30];
    char passwordInFile[30];
    int valid = 0;

    //Prompt and get Username
    printf("Enter Username: ");
    scanf("%s", username);

    //Prompt and get Password
    printf("Enter Password: ");
    scanf("%s", password);

    //Open the input file
    FILE * fptr = fopen(PASSWORD_FILE, "r");

    while (fscanf(fptr, "%s %s", usernameInFile, passwordInFile) == 2)
    {
        if (strcmp(username, usernameInFile) == 0 && strcmp(password, 
    passwordInFile) == 0)
        {
            valid = 1;
        }
    }

    fclose(fptr);
    return valid;
}


int memberMenu()
{
    int choice = 0;

    do
    {
        printf("Press 1 for author info\n");
        printf("Press 2 to Enter new student\n");
        printf("Press 3 to enter grade for existing student\n");
        printf("Press 4 to print student records\n");
        printf("Press 5 to save student records\n");
        printf("Press 6 to load student records\n");
        printf("Press 7 to logout\nEnter Selection? ");
        scanf("%d", &choice);
        printf("\n");

    } while (choice < 1 || choice > 7);

    return choice;
}

void print(char fn[1000][25], char ln[1000][25], char ids[1000][25], float  
    grades[1000][100], int counts[], int num)
{
    int i, j;
    float sum, avg;
    sum = 0;
    avg = 0;

    printf("%-15s %-15s %-10s %-8s %-8s\n", "First Name",
        "Last Name", "Std ID", "GPA", "Grades");

    for (i = 0; i < num; i++)
    {
        printf("%-15s %-15s %-10s", fn[i], ln[i], ids[i]);

        for (j = 0; j < counts[i]; j++)
        {
            sum += grades[i][j];
        }

        avg = sum / counts[i];
        sum = 0;
        printf("%-8.2f", avg);
        for (j = 0; j < counts[i]; j++)
        {
            printf("%-6.2f", grades[i]);
        }
        printf("\n");
    }
}

void save(char fn[1000][25], char ln[1000][25], char ids[1000][25], float   
    grades[1000][100], int counts[], int num)
{
    int i, j;
    float sum, avg;
    char fname[100];
    sum = 0;
    avg = 0;

    //Get file name
    printf("Enter Output File Name: ");
    scanf("%s", fname);

    FILE * fptr = fopen(fname, "w");

    fprintf(fptr, "%d\n", num);
    for (i = 0; i < num; i++)
    {
        fprintf(fptr, "%s %s %s %d ", fn[i], ln[i], ids[i], counts[i]);

        for (j = 0; j < counts[i]; j++)
        {
            fprintf(fptr, "%.2f ", grades[i]);
        }
        fprintf(fptr, "\n");
    }

    fclose(fptr);
}

void load(char fn[1000][25], char ln[1000][25], char ids[1000][25], float 
    grades[1000][100], int counts[], int * num)
{
    char fname[100];
    int cur = *num;
    int i, j, n, numStudents = 0;
    float grade;

    //prompt and get input file
    printf("Enter Input File Name: ");
    scanf("%s", fname);

    //open file to read
    FILE * fptr = fopen(fname, "r");
    fscanf(fptr, "%d", &numStudents);
    for (i = 0; i < numStudents && cur < 1000; i++)
    {
        fscanf(fptr, "%s %s %s %d", fn[cur], ln[cur], ids[cur], &n);
        for (j = 0; j < n && counts[i] < 100; j++)
        {
            fscanf(fptr, "%f", &grade);
            grades[i][counts[i]] = grade;
            counts[i] += 1;
        }
        cur += 1;
    }

    *num = cur;
    fclose(fptr);

}

void enterGPA(char ids[1000][25], float grades[1000][100], int counts[], int 
    num)
{
    char id[25];
    int i, idx;
    float gpa;

    idx = -1;

    printf("Enter Student ID: ");
    scanf("%s", id);

    //find student
    for (i = 0; i < num && idx == -1; i++)
    {
        if (strcmp(id, ids[i]) == 0)
        {
            idx = i;
        }
    }

    if (idx >= 0)
    {
        printf("Enter Grade: ");
        scanf("%f", &gpa);
        grades[idx][counts[idx]] = gpa;
        counts[idx] += 1;
    }
    else
    {
        printf("NO Such Student Exist In The System");
    }
}

Answer 1

我可以立即看到两个问题。

1. 在打印功能中您有

   printf("%-6.2f", grades[i];
   

   由于 grades 是一个二维数组，所以它应该是

   printf("%-6.2f", grades[i][j]
   

2. load 的函数声明不正确。应该是

   void load(char fn[1000][25], char ln[1000][25], char ids[1000][25],
      float grades[1000][100], int counts[], int *num);
   

   (注意int* num)

可能还有其他问题，但没有输入文本文件很难找出。