Doubly Linked List With Header Nodes

[usama shahid]

#include <iostream>
#include <string>
using namespace std;
class Student
{
private:
	string name;
	float cgpa;
	int id;            	 //id of a student  string name;  	//name of a student  float cpga;    	 	  //cgpa of a student. 
	Student *next;       //address of the next available object. 
	Student *prev;      //address of the previous available object. 

public:

	Student(int _ID = -1, float _CGPA = -1, string _name = "-1", Student* _prev = NULL, Student* _next = NULL)
	{
		id = _ID;
		cgpa = _CGPA;
		name = _name;
		next = prev = NULL;
	}
	friend class StudentList;
};
class StudentList
{
private:
	Student *head;//start of the list 
	Student *cursor;//current item of the list 
	Student *tail; //last item of the list 
	int theSize;
public:
	StudentList()
	{
		theSize = 0;
		head = new Student;
		tail = new Student;
		head->next = tail;
		tail->prev = head;
		head->prev - tail;
		tail->next = head;
		cursor = NULL;
	}
	void insert(const Student& obj)
	{
		if (head->next == tail)
		{
			Student *p= new Student(obj);
			head->next = p;
			p->next = tail;
			tail->prev = p;
			p->prev = head;
			cursor = p;
		}
		else
		{
			Student* tmp = new Student(obj.id, obj.cgpa, obj.name);

			tail->prev->next = tmp;
			tmp->next = tail;
			tmp->prev = tail->prev;
			tail->prev = tmp;

			theSize++;
			cursor = tmp;
		}
	}
	~StudentList()
	{
		Student *tmp = head;
		while (tmp != tail)
		{
			Student *junk = tmp;
			tmp = tmp->next;
			delete junk;
		}
		delete tail;
	}
	void showStructureForward()
	{
		if (isEmpty())
		{
			cout << endl << " *** list empty *** " << endl << endl;
			return;
		}

		cursor = head;

		do
		{
			cursor = cursor->next;

			cout << "  ID :: " << cursor->id << endl;
			cout << "CGPA :: " << cursor->cgpa << endl;
			cout << "Name :: " << cursor->name << endl << endl;

		} while (cursor->next != tail);
	}
	bool isEmpty()
	{
		if (head->next == tail)
			return true;

		return false;
	}
	void showStructureReverse()
	{
		if (isEmpty())
		{
			cout << endl << " *** list empty *** " << endl << endl;
			return;
		}

		cursor = tail;

		do
		{
			cursor = cursor->prev;

			cout << "  ID :: " << cursor->id << endl;
			cout << "CGPA :: " << cursor->cgpa << endl;
			cout << "Name :: " << cursor->name << endl << endl;

		} while (cursor->prev != head);
	}
	void remove(int iD)
	{
		if (cursor->id == iD)
		{
			Student *tmp = cursor;
			cursor = tmp->next;
			tmp->prev->next = tmp->next;
			tmp->next->prev = tmp->prev;
			delete tmp;
			theSize--;
		}
		else if (cursor->id == iD && cursor->next == tail)
		{
			Student *tmp = cursor;
			cursor = head;
			tmp->prev->next = tmp->next;
			tmp->next->prev = tmp->prev;
			delete tmp;
			theSize--;
		}
		else
		{
			Student *tmp = head;
			while (tmp->next != tail)
			{
				if (tmp->id == iD)
				{
					tmp->prev->next = tmp->next;
					tmp->next->prev = tmp->prev;
					delete tmp;
					theSize--;
				}
			}
		}
	}
	void search(float Cgpa)
	{
		if (isEmpty())
		{
			cout << ":List is empty " << endl;
			return;
		}
		else if (cursor->cgpa == Cgpa)
		{
			cout << "CGPA is : " << cursor->cgpa;
			cout << "ID is : " << cursor->id;
			cout << "Name is : " << cursor->name;
		}
		else
		{
			Student *tmp = head;
			while (tmp->next != tail)
			{
				if (tmp->cgpa == Cgpa)
				{
					cout << "CGPA is : " << tmp->cgpa;
					cout << "ID is : " << tmp->id;
					cout << "Name is : " << tmp->name;
				}
				tmp = tmp->next;
			}
		}
	}
	Student getCursor()
	{
		
		return *cursor;
	}
	bool gotoPrior()
	{
		if (cursor != head)
		{
			cursor = cursor->prev;
			return true;
		}
		return false;
	}
	bool gotoNext()
	{
		if (cursor->next != tail)
		{
			cursor = cursor->next;
			return true;
		}
		return false;
	}
	void gotoEnd()
	{
		cursor = tail->prev;
	}
	void gotoBeginning()
	{
		cursor = head->next;
	}
	void replace(const Student& newStd)
	{
		bool find = false;

		if (isEmpty())
		{
			cout << "List is empty ";
			return;
		}
		else
		{
			Student *tmp = head;
			while (tmp->next != tail)
			{
				if (tmp->id == newStd.id)
				{
					tmp->id = newStd.id;
					tmp->cgpa = newStd.cgpa;
					tmp->name = newStd.name;
					find = true;
				}
				tmp = tmp->next;
			}
			if (find == false)
			{
				insert(newStd);
			}

		}
	}
};