Write a program using inheritance in C++ to insert a node in the middle of Doubl

Question

Write a program using inheritance in C++ to insert a node in the middle of Doubly linked list .( using this code) but no need for deletion just the insert in the middle using inheritance.

#ifndef DLLIST
#define DLLIST

#include<iostream>

using namespace std;

template<class T>
class DLLNode {
  
public:
   T info;
   DLLNode<T> *next, *prev;
   DLLNode(){
       next = prev = 0;
   }
   DLLNode(T t, DLLNode<T> *n = 0, DLLNode<T> *p = 0) {
       info = t;
       next = n;
       prev = p;

   }

};

template<class T>
class DLL{
protected:
   DLLNode<T> *head=0, *tail=0;
public:
   void insertAtHead(T t) {
       head = new DLLNode<T>(t, head);
       if (tail != 0)// if at least two nodes;
      //if(head->nexttail!= 0)
           head->next->prev = head;
       else tail = head;
   }
   T deleteFromTail() {
       //if (head == 0) // in list is empty
           //return 0; // in most cases makes no sense;
       T t = tail->info; // (*tail).info
       tail = tail->prev;
       if (tail != 0) {
           delete tail->next;
           tail->next = 0;
       }
       else {
           delete head;
           head = 0;
         }
       return t;
     }

   bool isEmpty() {
       return head == 0;

   }
  
   template<class T>
   friend ostream& operator<<(ostream& out, const DLL<T>& dll);
};

template<class T>
ostream& operator<<(ostream& out, const DLL<T>& dll) {
   for (DLLNode<T> *p = dll.head; p!= 0; p = p->next)
       out << p ->info << ' ';
   out << endl;
   return out;
}

#include "stdafx.h"
#include "DLL.h"
#include <list>


using namespace std;

void testDLL() {
   DLL<int> dll;
   dll.insertAtHead(10);
   dll.insertAtHead(11);
   dll.insertAtHead(12);
   cout << dll;
   cout << dll.deleteFromTail() << endl;
   cout << dll;
   cout << dll.deleteFromTail() << endl;
   cout << dll;
   cout << dll.deleteFromTail() << endl;
   cout << dll;
   cout << dll.deleteFromTail() << endl;
}

void testSTLlist() {
   list <int> lst;
   lst.push_back(10);
   lst.push_back(20);
   lst.push_back(30);
   cout << lst << endl;
}

template<class T>
ostream& operator<<(ostream& out, list<T>& lst) {
   for (list<T>::iterator i = lst.begin(); i != lst.end(); i++)// overload
       out << *i << ' ';
   out << endl;
   return out;
}

int main()
{

   testDLL();
   testSTLlist()
    return 0;
}

Explanation / Answer

void insertAtMidpos(Node** head_ref, int x)
{

if (*head_ref == NULL)
*head_ref = getNode(x);
else {

  
Node* newNode = getNode(x);

Node* ptr = *head_ref;
int len = 0;

while (ptr != NULL) {
len++;
ptr = ptr->next;
}

int count = ((len % 2) == 0) ? (len / 2) :
(len + 1) / 2;
ptr = *head_ref;

while (count-- > 1)
ptr = ptr->next;

newNode->next = ptr->next;
ptr->next = newNode;
}
}

void display(Node* head)
{
while (head != NULL) {
cout << head->data << " ";
head = head->next;
}
}

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