c++ linked list creation linked list of linked list [closed] - c++

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the code send error in this line
course["CS"].student=new Course*[1];
i want create linked list of courses contain linked list of students
here is the code
struct Student{
string name;
int id;
int grade;
Student(string n, int i, int gd ){
name=n;
id=i;
grade=gd;
}
};
struct Course{
string C_Name;
Student **student;
int index;
void add_student(Student *new_student){
student[++index]=new_student;
}
};
Course course[4];
void init(){
course["CS"].student=new Course*[1];
}

Answer 1

Your code doesn't contain any kind of linked list, but only plain arrays.
Apart from that, the last line (course["CS"].student=new Course*[1];) contains some invalid syntax.
An integral or enum type must be used to access an array (strings or char[] wont work)
Assigning a Course** to a Student** object is not allowed
A linked list contains of nodes each having a pointer to the next node. The last node usually has a pointer with value nullptr (C++11) or 0 (older standard). Note: There is also a so-called double linked list, where every node also stores a pointer to the previous one.
A node contains all the data, that you want it to store.
Example:
struct Node {
Node* next;
// other node data here
};
To create a linked list, you first start with one node and set next = nullptr; // 0. To add another node just create a new one and change the pointer of the first one.
Example:
Node* node1 = new Node();
node1 -> next = nullptr;
Node* node2 = new Node();
node2 -> next = nullptr;
node1 -> next = node2;
You start to see a pattern. To insert at the front just create a new Node and set its next to the first already existing node. To insert between two nodes, say node1 and node2:
node1 -> next = newNode;
newNode -> next = node2;
To make it nice one usually writes a wrapper class containing functions such as
InsertNodeAt(Node* node, uint index);
Node* GetNodeAt(uint index);
RemoveNodeAt(uint index);
Since you have two different types of objects (Student and Curse), you might want to use templates and avoid writing a linked list class for each type.
If you want to create your linked list yourself, I recommend doing some additional research (google is your friend) as I have only mentioned a few things.
If you don't mind using the c++ standard library you might be interested in using the already pre-made linked list classes std::forward_list (standard linked list) and std::list (double linked list).

Answer 2

in c++ you didn't defined course["string"], so you may not use "CS" as an index to a Course type object
and *.student is a class Student's object, not Course type
#include <iostream>
#include <stdexcept>
using namespace std;
struct Student{
string name;
int id;
int grade;
Student(string n, int i, int gd ){
name=n;
id=i;
grade=gd;
}
};
struct Course{
string C_Name;
Student **student;
int index;
void add_student(Student *new_student){
student[++index]=new_student;
}
};
Course course[4];
void init(){
// Need allocate space for a new object of class "Course"
Course course;
course.student = new Student*[1];// "student" is Student type but not Course
}
int main()
{
try{
init();
}
catch(...){
return -1;
}
std::cerr <<"your debug info" <<endl;
return 0;
}
And in my own opinion, in c++ you may try reference and it's counter in class Course's definition to class Student. Using printer in this way may cause error unexpected.