Question

Can anyone change it to double linked list

#include<stdio.h>
#include<stdlib.h>
#include <iostream>
using namespace std;

struct Node
{
    int data;
    struct Node* next;
};

void printMiddle(struct Node *head)
{
    struct Node *slow_ptr = head;
    struct Node *fast_ptr = head;

    if (head!=NULL)
    {
        while (fast_ptr != NULL && fast_ptr->next != NULL)
        {
            fast_ptr = fast_ptr->next->next;
            slow_ptr = slow_ptr->next;
        }
        printf("The middle element is [%d]\n\n", slow_ptr->data);
    }
}

void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node =
        (struct Node*) malloc(sizeof(struct Node));

    new_node->data = new_data;

    new_node->next = (*head_ref);

    (*head_ref) = new_node;
}

void printList(struct Node *ptr)
{
    while (ptr != NULL)
    {
        printf("%d->", ptr->data);
        ptr = ptr->next;
    }
    printf("NULL\n");
}

int main()
{
    struct Node* head = NULL;
    int s;
    cout << "enter the size of the linkedlist" << endl;
    cin >> s;
    cout << " Linked list is: " << s << endl;
    for (int i=0; i<s; i++)
    {
        int x;
        cin>> x;
        push(&head, x);
        printList(head);
        printMiddle(head);
    }

    return 0;
}

Answer 1

If You Have Any Doubts Please Comment :-

#include<iostream>
#include<stdlib.h>
using namespace std;
struct Node{
   int data;
   struct Node*next;
   struct Node*prev;
};

void printMiddle(struct Node *head){
   struct Node*slow_ptr=head;
   struct Node*fast_ptr=head;
   if(head!=NULL){
       while(fast_ptr!=NULL && fast_ptr->next!=NULL){
           fast_ptr=fast_ptr->next->next;
           slow_ptr=slow_ptr->next;
       }
       printf("\n\nThe middle element is [%d]\n\n",slow_ptr->data);
   }  
}
void push(struct Node** head_ref, int new_data)
{
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
new_node->data = new_data;
new_node->next = (*head_ref);
new_node->prev = NULL;
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
(*head_ref) = new_node;
}
void printList(Node* node)
{
Node* last;
cout<<"\nTraversal in forward direction \n";
while (node != NULL)
{
cout<<" "<<node->data<<" ";
last = node;
node = node->next;
}
  
cout<<"\nTraversal in reverse direction \n";
while (last != NULL)
{
cout<<" "<<last->data<<" ";
last = last->prev;
}
}
int main(){
   struct Node*head = NULL;
   int s;
   cout<<"Enter the size of the linkedlist"<<endl;
   cin>>s;
   cout<<"Linkedlist is:" <<s<<endl;
   for(int i=0;i<s;i++){
       int x;
       cin>>x;
       push(&head,x);
       printList(head);
       printMiddle(head);
   }
   return 0;
}

Output :-