List Two Way

Data.h

#pragma once
#include <iostream>
#include <string>

using namespace std;

struct Data {
	unsigned long ID;
	string name;
	string surname;

	Data() {
		ID = NULL;
		name = surname = "";
	};

	unsigned int GetID() { return ID; }
	string GetName() { return name; }
	string GetSurname() { return surname; }
	Data Enter() {
		Data temp;
		cout << "Enter ID:"; cin >> temp.ID;
		cout << "Enter name:"; cin >> temp.name;
		cout << "Enter surname:"; cin >> temp.surname;

		return temp;
	}
	/*/
		std::stringstream s; s << this->GetData(); return s.str();
	*/

}; // Data

string PrintData(Data obj) {
	string out;
	out += obj.ID;
	out += obj.name;
	out += obj.surname;
	return out;
}

List.h

#pragma once 
#include <string>
#include "Node.h"

template<class T>
class List {
private:
	Node<T>* head;
	Node<T>* tail;
	unsigned int length;
public:
	List() {
		head = tail = NULL;
		length = 0;
	};

	Node<T>* GetHead() { return this->head; };
	Node<T>* GetTail() { return this->tail; };
	unsigned int GetLength() { return this->length; };
	void PushFront(Node<T>* node) {
		this->head == NULL ? InitializeEmptyHeadWith(node) : PushFrontWith(node);
	}
	void PushBack(Node<T>* node) {
		this->head == NULL ? InitializeEmptyHeadWith(node) : PushBackWith(node);
	}
	//Pop First element in List
	Node<T>* Pop() {
		auto temp = this->head;
		if (length == 1) {
			this->head = NULL;
			this->tail = NULL;
			this->length = this->length - 1;
		}
		else if(length >= 1)
		{
			this->head = this->head->next;
			this->head->previous = NULL;
			this->length = this->length - 1;
			return temp;
		}
	}
	T ElementAt(int index) {
		if (IsEmpty() || IndexOutOfBound(index)) return NULL;

		return (index == 0 ? GetHead() : index == length - 1 ? GetTail() : FindElement(index))->GetData();
	}
	std::string ToString() {
		auto temp = this->head;
		std::string s = "";
		while (temp) {
			s += temp->ToString();
			s += " -> ";
			temp = temp->next;
		}
		return s;
	}
private:
	bool IndexOutOfBound(int index) { return index > length ? true : false; }
	bool IsEmpty() { return length <= 0 ? true : false; }
	Node<T>* FindElement(int index) {
		if (index < this->length / 2)
		{
			auto temp = this->head;
			int i = 0;
			while (temp) {
				if (i == index) { return temp; }
				i++;
				temp = temp->next;
			}
		}
		else
		{
			auto temp = this->tail;
			int i = this->length - 1;
			while (temp) {
				if (i == index) { return temp; }
				i--;
				temp = temp->previous;
			}
		}
		return NULL;
	}
	void InitializeEmptyHeadWith(Node<T>* node) {
		this->head = node;
		this->tail = this->head;
		this->length = this->length + 1;
	}

	void PushFrontWith(Node<T>* node) {
		this->head->previous = node;
		node->next = this->head;
		this->head = node;
		this->length = this->length + 1;
	}

	void PushBackWith(Node<T>* node) {
		this->tail->next = node;
		node->previous = this->tail;
		this->tail = node;
		this->length = this->length + 1;
	}

}; // List

main.cpp

#pragma once
#include <iostream>
#include <string>
#include "List.h"
using namespace std;

int main() {
	List<Data> lista;
	int c = NULL;
	while (true)
	{
		cout << "================" << endl;
		cout << " 1. Get Length" << endl;
		cout << " 2. Push Front" << endl;
		cout << " 3. Push Back" << endl;
		cout << " 4. Pop" << endl;
		cout << " 5. Print List" << endl;
		cout << "================" << endl;
		cout << "Choice:";
		cin >> c;
		switch (c)
		{
		case 1:
			cout << "Length: " << lista.GetLength();
			break;
		case 2:
			cout << "Enter value:";
			lista.PushFront(new Node<Data>(Data().Enter()));
			break;
		case 3:
			cout << "Enter value:";
			lista.PushBack(new Node<Data>(Data().Enter()));
			break;
		case 4:
			lista.Pop();
			break;
		case 5:
			cout << lista.ToString();
			break;
		}

		cout << endl << endl;
	}
}

Node.h

#pragma once
#include <string>
#include <sstream>
#include "Data.h"

template<class T>
class Node {
private:
	T data;
public:
	Node* next;
	Node* previous;


	string(*test_ptr)(T) = PrintData;
	~Node() {};

	Node(T data) {
		next = previous = NULL;
		this->data = data;
	}
	std::string ToString() { return PrintData(data); }

private:
	T GetData() { return this->data; }
	Node();
	Node(const Node<T>&);
}; // Node