Traversing a linked list with a structure inside - c++

Question

So I a linked list of 4 students and inside each node for the linked list is a structure that holds some data about the students. I want to traverse this linked list and print the data inside each of the structures. I can traverse the linked list expect all the data print is 0. Any help would be much appreciated.
#include<stdlib.h>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<cstdlib>
using namespace std;
void displayGrades( struct Outer *O);
void calculateGrades(struct Outer *O);
void readGrades( struct Outer *O);
struct Inner{
int id;
string name;
double midterm1;
double midterm2;
double midtermTotal;
double lab_H;
double finalExam;
double total;
};
Inner i1;
struct Outer{
Inner data;
Outer *next;
};
struct Outer o1, o2, o3, o4;
int main()
{
readGrades(&o1);
calculateGrades(&o1);
displayGrades(&o1);
//o1.next = &o2;
/*
readGrades(&o2);
calculateGrades(&o2);
displayGrades(&o2);
//o2.next =&o3;
readGrades(&o3);
calculateGrades(&o3);
displayGrades(&o3);
//o3.next =&o4;
readGrades(&o4);
calculateGrades(&o4);
displayGrades(&o4);
//o4.next =NULL;
*/
Outer *ptro1;
ptro1 = new Outer;
Outer *ptro2;
ptro2 = new Outer;
Outer *ptro3;
ptro3 = new Outer;
Outer *ptro4;
ptro4 = new Outer;
Outer *head=ptro1;
ptro1->next = ptro2;
ptro2->next = ptro3;
ptro3->next = ptro4;
ptro4->next = NULL;
while(head!=NULL) // && i<=2)
{
cout<<"Student ID: "<<head->data.id<<endl;
cout<<"Student Midterm1: "<<head->data.midterm1<<endl;
cout<<"Student Midterm2: "<<head->data.midterm2<<endl;
cout<<"Student Labs and Homework: "<<head->data.lab_H<<endl;
cout<<"Student Final Exam: "<<head->data.finalExam<<endl;
head = head->next;
}
return 0;
}
void readGrades(struct Outer *O){
cout<<"Enter the student's id: "<<endl;
cin>>o1.data.id;
cout<<"Enter the student's midterm #1 grade: ";
cin>>o1.data.midterm1;
cout<<"Enter the student's midterm #2 grade: ";
cin>>o1.data.midterm2;
cout<<"Enter the student's lab and homework grade: ";
cin>>o1.data.lab_H;
cout<<"Enter the student's final exam grade: ";
cin>>o1.data.finalExam;
}
void displayGrades(struct Outer *O){
cout<<"The students final grade is: ";
if(O->data.total>=90)
{
cout<<"A"<<endl;
}
else if(O->data.total<=89 && O->data.total>=80)
{
cout<<"B"<<endl;
}
else if(O->data.total<=79 && O->data.total>=70)
{
cout<<"C"<<endl;
}
else if(O->data.total<=69 && O->data.total<60)
{
cout<<"F"<<endl;
}
}
void calculateGrades(struct Outer *O){
O->data.midtermTotal=(((O->data.midterm1/50)+(O- >data.midterm2/50))/2)*35;
O->data.lab_H=(O->data.lab_H/20)*25;
O->data.finalExam=(O->data.finalExam/100)*40;
O->data.total=O->data.midtermTotal+O->data.lab_H+O->data.finalExam;
//displayGrades();
}

Answer 1

In the below function you need to use O as you are passing it but you are using
o1 which will overwrite every time
void readGrades(struct Outer *O)
{
cout<<"Enter the student's id: "<<endl;
cin>>O->data.id;
cout<<"Enter the student's midterm #1 grade: ";
cin>>O->data.midterm1;
cout<<"Enter the student's midterm #2 grade: ";
cin>>O->data.midterm2;
cout<<"Enter the student's lab and homework grade: ";
cin>>O->data.lab_H;
cout<<"Enter the student's final exam grade: ";
cin>>O->data.finalExam;
}

Answer 2

You should create a constructor that initializes the member variables to 0. Most of compilers do not do that by default.
struct Inner{
Inner() : id(0),midterm1(0),midtermTotal(0), lab_H(0), finalExam(0), total(0)
{
}
int id;
string name;
double midterm1;
double midterm2;
double midtermTotal;
double lab_H;
double finalExam;
double total;
};