Design a doubly linked list and perform the following operations: 1)Add nodes to both front and rear 2)Display the list, 3)Delete nodes at front.tail and nth position


#include

using namespace std;

class Node
{
    public:
    int data;
    Node *prev, *next;
    Node()
    {
        data=NULL;
        prev=NULL;
        next=NULL;
    }   
};

class dll
{
    private:
        Node *header;
    public:
        dll(){
            header=NULL;
        }
        void createList();
        void displayList();
        void insertEnd();
        void deleteFirstNode();
        void deleteLastNode();
        void deleteNthNode();
};

void dll::deleteFirstNode()
{
    if(header)
    {
        Node *temp;
        temp=header;
        header=temp->next;
        header->prev=NULL;
        delete temp;
    }
    else
    {cout<<"\nThe list is empty!\n";}
    return;
}

void dll::deleteLastNode()
{
    if(header)
    {
        Node *temp, *last;
        temp=header;
        while(temp)
        {
            last=temp;
            temp=temp->next;
        }
        last->prev->next=NULL;
        delete last;
        delete temp;       
    }
    else
    {cout<<"\nThe list is empty!\n";}
    return;
}

void dll::deleteNthNode()
{
    if(header)
    {
        Node *temp, *last;
        temp=header;
        int position=0, counter=0;
        cout<<"Enter the node position that you want to delete: \t";
        cin>>position;
        if(position>=0)
        {
            while(counter!=position && temp)
            {
                last=temp;           
                temp=temp->next;
                counter++;
            }
            if(temp)
            {
            cout<<"\nThe node that you want to delete has value:\t\n"<data;
            last->prev->next=temp;
            temp->prev=last->prev;
            delete last;           
            }
            else{cout<<"\nThe list does not contain that many elements\n";}
        }
    }
    return;
}

void dll::insertEnd()
{
    if(header==NULL)
    {
        createList();
    }
    else
    {
        Node *newNode, *temp, *last;
        newNode=new Node;
        cout<<"Enter the value for the node:\t";
        cin>>newNode->data;
        temp=header;
        while(temp)
        {
            last=temp;
            temp=temp->next;
        }
        newNode->next=NULL; //newNode is the new last node
        newNode->prev=last;
        newNode->prev->next=newNode;           
    }
    return;
}

void dll::createList()
{
    int in_val;
    Node *temp;
    temp=new Node;
    cout<<"Enter the value for the node:\t";
    cin>>temp->data;
    if(header == NULL)
    {
        //This is the first node in the double linked list
        temp->next=NULL;
        temp->prev=NULL;       
    }
    else
    {
        //If this is a new node at the front of an already populated linkedlist
        temp->next=header;
        temp->next->prev=temp;
        header=temp;
    }
    header=temp;
    return;
}

void dll::displayList()
{
    Node *temp, *last;
    temp=header;
    cout<<"Display the list from first to last using the NEXT pointer.\n";
    while(temp)
    {   
        cout<data<<"\t"<<endl;
        last=temp;
        temp=temp->next;
    }
    /*if(last)
    {
        cout<<"Display the list from last to last using the PREV pointer.\n";
        while(last)
        {
            cout<data<<"\t"<<endl;
            last=last->prev;       
        }
    }*/
}

void main()
{
    cout<<"******This is a Doubly Linked List Demo******"<<endl;
    int choice=0;
    dll objDLL;
    do{
        cout<<"Enter the opration you want to perform: ";
        cout<<"\n1). Add a node at front of the list";
        cout<<"\n2). Display a node";
        cout<<"\n3). Add a node at end of the list";
        cout<<"\n4). Delete the node at head of the list";
        cout<<"\n5). Delete the node at tail of the list";
        cout<<"\n6). Delete the node at nth position of the list";
        cout<<"\n7). Exit\t";
    cin>>choice;
    switch(choice)
    {
        case 1: objDLL.createList(); break;
        case 2: objDLL.displayList(); break;
        case 3: objDLL.insertEnd(); break;
        case 4: objDLL.deleteFirstNode();break;
        case 5: objDLL.deleteLastNode();break;
        case 6: objDLL.deleteNthNode();break;
        case 7: exit(0);
        default: cout<<"\n Invalid operation/input detected. Please try again later.";
    }   
    }while(choice!=7);
}   

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