c - 插入成绩和GPA对学生不起作用

我的代码要求我输入.txt文件中的名称，然后如果这些名称有效，我就可以登录。

到目前为止，我已经做到了。成功登录后，可以按选项2添加一个新学生。现在，我对选项3犯了一个错误。选项3要求我输入学生的成绩。点击选项3后，它会询问我成绩，每当我输入成绩时，程序就会崩溃。我希望它显示GPA。以及所有收到的成绩。这是我在代码中写的。我不确定算法在哪里出错。

//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");
}
}

最佳答案

grades[i][counts[i]] = grade;：选中counts[i]。我认为int numGrades[1000];没有初始化。您使用未初始化的值。
                      – BLUEPIXY


BLUEPIXY是非常正确的，只有上面的行在函数load()中，而使用valgrind运行时，则显示选项3在函数enterGPA()中存在相同的问题：

    grades[idx][counts[idx]] = gpa;

  尝试int numGrades[1000];-> int numGrades[1000] = {0};
                      – BLUEPIXY


这确实在所有地方都解决了问题。

关于c - 插入成绩和GPA对学生不起作用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41009060/