DoubleListInt, C++ (gcc)

DoubleListInt

//g++  7.4.0
//Double Linked List (int)
// class code credit wikihut, internet

#include <iostream>
using namespace std;
struct node {
int data;
node* next;
node* prev;
};
struct node* head;
struct node* tail;

void init()
	 {
	 	head=NULL;
	 	tail=NULL;
	 }
 
 class Double_List
 {
 	public:
 		void createlist(int n);
 		void addbegin(int n);
 		void display();
 		void reverse();
node* gethead() { return head;}
node* gettail(){return tail;}
void after(node *q, int v)
    {
node* p = new node;
       p->data=v;
        p->next=q->next;
        q->next = p;
        p->prev= q;
    }

void remove();
bool
isempty()
    {
    if (head == NULL)
    return true;
    return false;
    }

};

void Double_List::createlist(int n)
  { 
	struct node *newnode;
	newnode=new node;
	newnode->data=n;
	 if(head==NULL)
	 {
	 	head=newnode;
	 	newnode->prev=NULL;
	 	newnode->next=NULL;
	 	tail=newnode;
	   }  
	else
	{
		newnode->prev=tail;
		tail->next=newnode;
		newnode->next=NULL;
		tail=newnode;
	}
  }
  
  void Double_List::addbegin(int n)
  {
  	if(head==NULL)
  	{
  		cout<<" Empty list : \n";
  		return;
	  }
  	 node *temp=new node;
  	 temp->data=n;
  	 temp->prev=NULL;
  	 temp->next=head;
  	 head->prev=temp;
  	 head=temp;
  	 
  }
  
  
  
  
  void Double_List::display()
  {
  	node *q;
  	 if(head==NULL)
  	 {
  	 	cout<<" List empty.. \n";
  	 	return;
	   }
	   q=head;
	   cout<<"\nThe Double Linked list is \n";
	   while(q!=NULL)
	    {
	    	cout<<q->data<<" <--> ";
	    	q=q->next;
		}
  }
  
  void Double_List::reverse()
  {
  	node *r;
  	 if(tail==NULL)
  	 {
  	 	cout<<"EMPTY list: \n";
  	 	return;
	   }
	else
	{
		r=tail;
	 while(r!=NULL)
	 {
	 	cout<<r->data<<" <--> ";
	    
	 	r=r->prev;
	 	
	 }
	}
  }

void Double_List:: remove()
    {
    
    if(isempty())
    {
    cout<<"is empty";
        
    }
else if (head == tail){
     
            delete head;
        head= tail =NULL;
        }
        else
        {
        node* temp, *temp2;
            temp2= tail;
            temp= head;

while (temp->next!= NULL)
{
temp2= temp;
temp=temp->next;
}
tail = temp2;
tail->next=NULL;
            delete temp;
while(temp->prev != NULL)
{ temp= temp2; temp2= temp2->prev;}
head = temp; tail->prev= NULL;
delete temp2;
        }
    }

int main()
{
init();
Double_List dl;
dl.createlist(10);
dl.createlist(11);

dl.createlist(12);
dl.addbegin(9);

dl.display();
cout<<endl;
cout<<"The reverse is:\n";
dl.reverse();

dl.remove();
dl.after(dl.gethead()->next->next,11);
dl.after(dl.gettail(),15);
dl.display();

return 0;
}


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