Nested structure function in c++ - c++

Question

I'm having trouble with one of my assignments (or maybe I'm overthinking it?)
I need to create
a function to take integer parameters for number of students and tests.
Allocate the memory needed for the array of students and the array of test scores for each student.
Return a pointer to the array of Student structures. No display output is done in this function.
int main()
{
int studentNum;
int testNum;
cout << "How many students are there?\n";
cin >> studentNum;
cout << "How many tests are there?";
cin >> testNum;
system("pause");
return 0;
}
my function
GradeBook *initArrays(int s, int t)
{
GradeBook *ptr;
// Allocate the array of Student structures.
ptr = new GradeBook[s];
// Allocate an array of ints (to hold test scores)
// for each element of the array of Student structures.
for (int count = 0; count < s; count++)
{
ptr[count].tests = new int[t];
}
// Return a pointer to the array of structures.
return ptr;
}
edit: I have edited my function, could i get some opinions on that?

Answer 1

if you are writing this in c++, use classes. if i understand correctly, you should create a structure to save a students id,name,or something and a corresponding grade?
something like:
class Test{
public:
int id;
int grade;
Test(int id, int grade){
this->id = id;
this->grade = grade;
}
};
class Student{
public:
int id;
std::string name;
std::vector<Test> tests;
Student(int id, std::string name)
{
this->id = id;
this->name = name;
}
};
int main(){
vector<Student> students;
int studentnum;
for (int i = 0; i < studentnum; i++){
students.push_back(Student(i, "name"));
//insert all tests of the student by calling students[i].tests.push_back(Test(id, grade))
}
}
this way you don't have to allocate memory, which you can easily overlook freeing.
edit:
this is very basic and not a sophisticated solution, as the properties of the classes are all public.
edit 2:
typedef struct Test{
int id;
int grade;
}Test;
typedef struct Student{
int id;
std::string name;
Test * tests;
}Student;
int main(){
Student * students;
int studentnum;
students = (Student*)malloc(sizeof(Student)*studentnum);
for (int i = 0; i < studentnum; i++){
students[i]->id = id;
students[i]->name = "name";
student[i]->tests = (Test*)malloc(sizeof(Test)*numberofgradesofthatstudent);
for (int j = 0; j < numberofgradesofthatstudent; j++)
{
students[i]->tests[j]->id = testid;
students[i]->tests[j]->grade = grade;
}
}
}
this is schematic! new and malloc reserve memory on the heap, do not forget to free everything when you are done with it.

Answer 2

As said a little above, be careful using brackets {} to delimit your blocks.
Secondly,the syntax:
array[studIndex].Tests
supposes that the value array[studIndex] (here an integer) has a member value named Tests. But in this case it doesn't.
Think about your problem: you need to store two values "connected" to one another in a static array. The way I see it, you should try on with two dimensional arrays:
int 2dArray[nbStudents][nbTests];
If you don't want to bother with 2dimensional arrays, you can also try
int 2dArray[nbStudents * nbTests];
But for conveniance, it is often better to use 2d arrays.
Also, think about declaring your array before the for loops in your function.
Then concatenate two for loops as you did and I'll let you think about the rest...