task 3( ds lab 6) 3rd sem

#include<bits/stdc++.h>
using namespace std;
struct node
{
    int data;
    struct node *next;
    struct node *prev;
};
typedef struct node Node;
Node* create_node(int item, Node *next,Node*prev)
{
    Node* new_node=new Node();
    if(new_node==NULL)
        cout<<"Error"<<endl;
    else
    {
        new_node->data=item;
        new_node->next=next;
        new_node->prev=prev;
    }
    return new_node;

}
Node* prepend(int item,Node* head)
{
    Node* new_node=create_node(item,head,NULL);
    return new_node;
}
Node* append(int item,Node *head)
{
    Node *new_node=create_node(item,NULL,NULL);
    if(head==NULL)
        return new_node;
    else
    {
        Node* current=new Node();
        current=head;
        while(current->next!=NULL)
            current=current->next;
        current->next=new_node;
        new_node->prev=current;
    }
    return head;
}
Node* insertn(int item,Node* head,int key)
{
    Node* new_node=create_node(item,NULL,NULL);
    if(head==NULL)
        cout<<"Error"<<endl;
    else
    {
        Node *current=new Node();
        current=head;
        while(current!=NULL&&current->data!=key)
            current=current->next;
        if(current!=NULL)
        {
            new_node->next=current->next;
            current->next=new_node;
            new_node->prev=current;
        }
        else
            cout<<"Value not found"<<endl;
    }
    return head;
}
void display(Node *head)
{
    cout<<"Linked list:"<<endl;
    while(head!=NULL)
    {
        cout<<head->data<<" ";
        head=head->next;
    }
    cout<<endl;
}

int main()
{
    Node*head=NULL;
    int t;
    cout<<"Number of test cases"<<endl;
    cin>>t;
    for(int i=0; i<t; i++)
    {
        cout<<"Enter 1 to prepend, 2 to append and 3 to insert"<<endl;
        int n;
        cin>>n;
        cout<<"Enter the value"<<endl;
        int item;
        cin>>item;
        if(n==1)
        {
            head=prepend(item,head);
            display(head);
        }
        else if(n==2)
        {
            head=append(item,head);
            display(head);
        }
        else if(n==3)
        {
            cout<<"Enter the key"<<endl;
            int key;
            cin>>key;
            head=insertn(item,head,key);
            display(head);
        }
    }
}