使用嵌套结构将结构作为引用传递时出错

#include <iostream>
#include <string>

struct Class
{
std::string name;
int units;
char grade;
};
struct Student
{
std::string name;
int id;
int num;
double gpa;
Class classes[20];
};
int get_info(Student students[100],const int);
double get_gpa(Class local_classes[20],const int);
int main()
{
const int MAX_STUDENTS = 100;
int num_of_students;
Student students[MAX_STUDENTS];
num_of_students = get_info(students,MAX_STUDENTS);
for (int i = 0; i < num_of_students; i++)
{
int amount_classes = students[i].num;
std::cout << "n*******x2 = " << students[i].name;
std::cout << "n*******Units: " << students[i].classes[0].units;
students[i].gpa = get_gpa(students[i].classes,amount_classes);
std::cout << "nGPA of " << students[i].name << " is: " << students[i].gpa;
}
return 0;
}
int get_info(Student students[100],const int MAX)
{   
int counter = 0, local_id;
while (counter < MAX && students[counter].id != -99)
{
std::cout << "Enter the Student's ID: ";
std::cin >> local_id;
std::cin.ignore();
if (local_id != -99)
{
students[counter].id = local_id;
students[counter].gpa = 0.0;
std::cout << "nEnter the Student's name: ";
std:getline(std::cin,students[counter].name);
std::cout << "nEnter the Student's number of classes: ";
std::cin >> students[counter].num;
std::cin.ignore();
for (int i = 0; i < students[counter].num; i++)
{
Class students_classes = students[counter].classes[i];
std::cout << "Enter the name of class #" << i << ": ";
std::getline(std::cin, students_classes.name);
std::cout << "Enter the units of " << students_classes.name << ": ";
std::cin >> students_classes.units;
std::cout << "Enter the grade recieved for " << students_classes.name << ": ";
std::cin >> students_classes.grade;
std::cout << "************* = " << students_classes.grade;
std::cin.ignore();
}
}
counter++;
return counter;
}
}
double get_gpa(Class local_classes[20],const int classNum)
{
int counter = 0;
char grade;
int intGrade = 0, intGradeTotal = 0, units = 0, unitsTotal = 0, numerator = 0;
double num = 0.0;
while (counter < classNum)
{
grade = local_classes[counter].grade;
std::cout << "nGrade for this class is: " << grade;
std::cout << "nGrade for this class is: " <<  local_classes[counter].grade;
units = local_classes[counter].units;
std::cout << "nUnits for this class is: " << units;
switch (grade)
{
case 'A':
intGrade = 4;
break;
case 'B':
intGrade = 3;
case 'C':
intGrade = 2;
break;
case 'D':
intGrade = 1;
break;
case 'F':
intGrade = 0;
break;
}
unitsTotal += units;
std::cout << "nAll units = " << unitsTotal;
num = intGrade * units;
std::cout << "nNum = " << num;
numerator += num;
counter++;
}
std::cout << numerator << "/" << unitsTotal;
std::cout << "nAnswer is: " << numerator / unitsTotal;
return 0.0;
}

你好。我正在为类做作业，我正在尝试在函数get_gpa()中做一些数学运算，但我遇到了麻烦，因为由于某种原因我无法弄清楚Students结构内嵌套结构中的信息在函数get_info()完成后没有保存。例如，在get_info()功能结束时，询问收到的成绩，如果用户输入"A"，则在支票中打印出来。(紧接着)，但是在功能完成后检查时它不再存在。这真的让我感到困惑，最大的问题是我不知道我到底做错了什么，否则我会试图修复它。由于这个错误，get_gpa()的数学不起作用，因为它完全基于一个开关语句，该语句假设local_classes[counter].grade中有值。如果你运行我的代码，我已经添加了调试语句来帮助显示整个事情的下水道。