Implementation of Double link list in c++ 

 
#include<iostream>

using namespace std;



struct Node

{

	int data;

	Node* next;

	Node* prev;

};



Node* first = NULL;

Node* last = NULL;



void insertAtLast(int val)

{

	Node* new_node = new Node;

	new_node->data = val;

	if (last == NULL)

	{

		new_node->next = new_node->prev = NULL;

		first = last = new_node;

	}

	else

	{

		new_node->next = NULL;

		new_node->prev = last;

		last->next = new_node;

		last = new_node;

	}

}



void insertAtFirst(int val)

{

	Node* new_node = new Node;

	new_node->data = val;

	if (first == NULL)

	{

		new_node->next = new_node->prev = NULL;

		first = last = new_node;

	}

	else

	{

		new_node->prev = NULL;

		new_node->next = first;

		first->prev = new_node;

		first = new_node;

	}

}



void traverseFirst()

{

	Node* new_node = new Node;

	new_node = first;

	while (new_node != NULL)

	{

		cout << new_node->data << " ";

		new_node = new_node->next;

	}

	cout << endl;

}



void traverseLast()

{

	Node* new_node = new Node;

	new_node = last;

	while (new_node != NULL)

	{

		cout << new_node->data << " ";

		new_node = new_node->prev;

	}

	cout << endl;

}



void deletefirst()

{

	Node* new_node = new Node;

	new_node = first;

	if (new_node == NULL)

	{

		cout << "List Empty" << endl;

		return;

	}

	first = first->next;

	if (first != NULL)

	{

		first->prev = NULL;

	}

	delete new_node;

}



void deletelast()

{

	Node* new_node = new Node;

	new_node = last;

	if (new_node == NULL)

	{

		cout << "List Empty" << endl;

		return;

	}

	last = last->prev;

	if (last != NULL)

	{

		last->next = NULL;

	}

	delete new_node;

}



int main()

{

	insertAtLast(10);

	insertAtFirst(20);

	traverseFirst();

	deletefirst();

	traverseLast();

	deletelast();

	traverseLast();

	cout << endl;

	return 0;

}