/*
* File: DoublyLinkedList.cpp
* Author:
*
*
*/

#include "DoublyLinkedList.hpp"
#include <iostream>
using namespace std;

/**
* constructor
* all pointer points to null
*/
DoublyLinkedList::DoublyLinkedList() {
head = 0;
tail = 0;
}

/**
* destructor
*/
DoublyLinkedList::~DoublyLinkedList() {
// clear all allocated memory
clear();
}

/**
* add to head of the list
* @param val node's value
*/
void DoublyLinkedList::addToHead(int val) {

// allocate memory
Node * n = new Node();
// set its value
n->setVal(val);
// set address of next pointer
n->setNext(head);

// the list is empty at the moment
if (tail == 0) {
   tail = n;
} else {
   // the list isn't empty at the moment
   head->setPrev(n);
}
// add to head so head pointer points to the newly created node
head = n;
}

/**
* add to tail of the list
* @param val node's value
*/
void DoublyLinkedList::addToTail(int val) {

// allocate memory
Node * n = new Node();
// set its value
n->setVal(val);
// set address of previous pointer
n->setPrev(tail);

// the list is empty at the moment
if (tail == 0) {
   head = n;
} else {
   // the list isn't empty at the moment
   tail->setNext(n);
}
// add to tail so tail pointer points to the newly created node
tail = n;
}

/**
* remove head of the list
*/
void DoublyLinkedList::deleteHead() {

// empty list
if (head == 0) {
   return;
}

// pointer points to the head
Node * tmp = head;

// move head to the next node
head = head->getNext();

// list is empty now
if (head == 0) {
   tail = 0;
} else {
   // list isn't empty
   head->setPrev(0);
}
// free a block of memory
delete tmp

Develop a game. Suppliers enter the game to increase their profits...