C++ Double Linked list. I am having difficulties implementing the double linked list into the programDList.cpp

#include

using namespace std;

class Item

{

public:

int val;

Item *next, *pre;

Item()

{

val =0;

next=0;

pre=0;

}

Item(int val)

{

this->val = val;

next=0;

pre=0;

}

};

class DLinkedList

{

int size;

Item *front;

Item *back;

public:

DLinkedList();

DLinkedList(const DLinkedList &list);

void push_back(Item *a);

void push_front(Item *a);

Item * pop_front();

Item * pop_back();

void insert(Item *a, int t); // insert the item a after the t-th element

void insertlist(DLinkedList *list, int t); // insert the whole list a after the t-th element

void display(ostream &out);

int getSize();

Item * getfront();

Item * getback();

void swap(Item *p, Item *q); //swap two items pointed by p and q, you can assume that p and q are something in the list

Item * extractmin(Item * start); // return the pointer of the min element after "start",

// here you can assume user will always input a valid pointer start that points to an item in the list

Item * extractmax(Item * start); // return the pointer of the max element after "start"

};

class myStack

{

DLinkedList list;

public:

myStack();

int getSize();

void in(Item *a);

Item *top();

void out();

};

class myQueue

{

DLinkedList list;

public:

myQueue();

int getSize();

void in(Item *a);

Item *front();

void out();

};

int main() {

return 0;

}

In this assignment, you are given several classes in the cpp file "DList.cpp". Your task is to complete the implementation of the classes specified as below. You need to submit a single cpp file that contains everything about your source code. It must be compilable and executable. Do not submit things irrelevant (such as .exe) etails are described below. 1 Your Taslk You are given a class "Item" that contains one integer value, and two pointers. You are going to build a doubly linked list class DLinkedList. I describe the tasks below Task 1: Implement the constructors (default and copy) of DLinkedList. You need to make sure that the copy constructor makes a separate copy of the list. Task 2: Implement push back, push front, pop back, pop front, get front, get back, display, swap. The functions are pretty self explanatory from their names Task 3: Implement Inserts. You should handle "insert an item" and "insert a list" Task 4: Implement extract min, extract max. They return the pointer to the min/max item in the list. If there is a tie, then choose arbitrarily among the mins/maxes. Task 5: Implement classes myQueue and myStack using DLinkedList. Do not re-write codes. (This task is pretty easy. There should not be any loops) Task 6: Design some tests to test your DLinkedList in the main function. You don't need to test your Stack nor Queue, as checking them is easy, assuming your DLinkedList is correct