I Got a assignment of linklist from my DSA teacher i did all my task except overloading subscript operator in linklist everytimes it give me !error segmation fault(core dumped) So kinldy please tell me how to overload subscript operator and also check is my copy constructor is correct or not?

Assignment link : Assignment

MY CODE :

#include <iostream>
using namespace std;
class LinkedList
{
private:

class Node
{
public:
int data;
Node * next;
Node(int data)
{
    this->data = data;
    this->next = NULL;
}
};
public:
Node *head;
LinkedList(){
head = NULL;
}
//Write a copy constructor. Also copy must be deep.
LinkedList(LinkedList& S)
    {
        head = S.head;
    }
//Overload [] operator. Use for loop in main to display it. 
void operator[](int i) {
    head->data = i;
}
void InsertAtEnd(int data){
    if (head == NULL)
        {
            head = new Node(data);
            return;
        }
        Node * temp = head;
        while (temp->next != NULL)
        {
            temp = temp->next;
        }
        temp->next = new Node(data);
    
    }
void Insert(int d1, int d2)//Add the node of data d2 after the node with data d1. If d2 is not available add it to the end.
{
    if (head == NULL)
        {
            Node * n = new Node(d2);
            n->next = head;
            head = n;
            return;
        }
        Node * temp = head;
        while (temp != NULL)
        {
            if (temp->data == d1)
            {
                Node * temp1 = temp->next;
                temp->next = new Node(d2);
                temp->next->next = temp1;
            }
            temp = temp->next;
        }
}
void Delete(int data){
     Node * todelete;
            if(head->data == data){
                todelete = head;
                head = head->next;
                free(todelete);
                return;
            }
            Node *temp = head;
            while(temp->next != NULL){
                if(temp->next->data == data){
                todelete = temp->next;
                temp->next = temp->next->next;
                free(todelete);
                break;
            }
                    temp = temp->next;
            }
} // Deletes a node with data.
int getSize(){
    Node * temp = head;
        int size = 0;
        while(temp != NULL){
        temp = temp->next;
        size  ; 
        }
        return size;
} //returns the count of elements in the list
bool IsEmpty(){
    if(head == NULL){
        return true;
    }
    else{
        return false;
    }
} //Returns true if empty.
void Merge(Node * list){
    //merge
    Node * temp  = head;
    while(temp != NULL){
        if(temp->next == NULL and list != NULL){
            temp->next = list;
            break;
        }
        temp = temp->next;
    }

    //DISPLAY
        while(head!=NULL){
            cout<<head->data<<"->";
            head=head->next;
        }
        cout<<"NULL"<<endl;
} //Merges the to the calling class.
void Erase(){
    Node * erase;
    while(head!= NULL){
        erase = head;
        head = head->next;
        head = NULL;
    }
    free(erase);

} //Deletes every node in an array.
void SelectiveErase(int num) //Find num and delete everything after num.
{
     Node * temp = head;
     Node * todelete;
        while(temp != NULL){
            if(temp->data == num){
                Node * erase = temp->next;
            while(temp->next != NULL){
                erase = temp->next;
                temp->next = temp->next->next;
                temp->next = NULL;
            }
                free(erase);
                break;
            }
                temp = temp->next;
        }
}
int FindNCount(int find)//Find and return count of all occurrence.
{
    int counter  = 0;
    bool flag = false;
    Node * temp = head;
    while(temp->data!= find){
        temp = temp->next;
        counter  ;
}
        return counter;
}
int RemoveDuplicate(int find)//Find and remove every duplicate element in the list. Make //elements unique.
{
    Node * temp = head;
    Node *temp1;
    while(temp != NULL){
        temp1 = temp;
        while(temp1->next != NULL){
             if(temp->data == temp1->next->data and temp->data == find and temp1->next->data == find){
                        Node *todelete = temp1->next;
                        temp1->next = temp1->next->next;
                        free(todelete);
             }
             else{
                temp1 = temp1->next;
             }
        }
        temp = temp->next;
    }
    return find;

}
void FindNReplace(int find, int data)//Find and replace all occurrence recursively.
{
     Node * temp = head;
            while(temp != NULL){
                if(temp->data == find){
                    temp->data = data;
                    break;
                }
                    temp = temp->next;
            }


}
void Display(){
    static Node * temp= head;
    if(temp == NULL){ cout << "NULL" << endl; return;}
    cout << temp->data<<"->";
    temp = temp->next;
    Display();
}
};
void Swap() // swap the contents of one list with another list of same type and size. Also write parameter
{
    LinkedList L,L1; 
    cout<<"AFTER SWAPING THE VALUE OF FIRST LIST \n";
    while(L.head != NULL && L1.head != NULL){
        int temp = L.head->data;
        L.head->data = L1.head->data;
        L1.head->data = temp;
        cout<<L.head->data<<"\n";
        L.head = L.head->next;
        L1.head = L1.head->next;
    }
    cout<<endl;
}
int main()
{
// You must call Display function after every function.
    LinkedList L{};
    L[23];
    // LinkedList L1;
    
    // L1.InsertAtEnd(5);
    // L1.InsertAtEnd(6);
    //L.Erase();
    // cout<<L.FindNCount(1)<<endl;
    //L.SelectiveErase(2);
    //L.Display();
    //L.Merge(L1.head);
    //L.RemoveDuplicate(2);
    //L.Display();
    //Swap();
return 0;
}

CodePudding user response：

This behavior is expected because you access element of head, when it is NULL. In main you have created empty list, for which head == NULL. So in next statement you should get segmentation fault. To fix you can do the following.

void operator[](int i) {
    if(head == NULL)
    {
        head = new Node(i);
        return;
    }
    head->data = i;
}

It will create the head node if your list is initially empty.