#include <iostream>
#include <crtdbg.h>

using namespace std;

//structure
struct sNode	{
	int m_data;
	sNode* m_next;
};

//function prototypes
void addTail(sNode*&, int);
void addHead(sNode*&, int);
void f_display(sNode*);
void r_display(sNode*);

int main()	{
	int data = 0;			//integer data input for linked list
	char cMenu;				//menu choice
	bool bExit = false;		//exit or not (menu choice)

	//enable memory leak check
	_CrtSetDbgFlag (_CRTDBG_ALLOC_MEM_DF |_CRTDBG_LEAK_CHECK_DF | _CRTDBG_CHECK_ALWAYS_DF);
	
	sNode* pHead(0);
	sNode* pCurrent = pHead;

	do	{
		system("cls");
		cout << "Linked List\n\n\ta. display nodes forward.\n\tb. display nodes in reverse.\n\tc. add node to head.\n\td. add node to tail.\n\te. exit.\n\n";
		cout << "Your selection: ";
		cin >> cMenu;
		switch(cMenu)	{
			case 'a':
			case 'A':
				//display forward
				f_display(pHead);
				system("pause");
				break;
			case 'b':
			case 'B':
				//display reverse
				r_display(pHead);
				system("pause");
				break;
			case 'c':
			case 'C':
				//add node to head
				cout << "Enter integer value to store: ";
				cin >> data;
				addHead(pHead, data);	
				break;
			case 'd':
			case 'D':
				//add node to tail
				cout << "Enter integer value to store: ";
				cin >> data;
				addTail(pHead, data);			
				break;
			case 'e':
			case 'E':
				bExit = true;
				break;
			default:
				cout << "Invalid selection.\nPlease try again.\n";
				system("pause");
		}
	}while(!bExit);

	//gtfo!
	sNode* pDelete(0);
	pCurrent = pHead;
	while(pCurrent)	{
		pDelete = pCurrent;
		pCurrent = pCurrent->m_next;
		delete pDelete;
	}
	
	return 0;
}

void addTail(sNode* &pHead, int data)	{
	//pointer definition
	sNode* pCurrent;
	sNode* pNew = new(nothrow) sNode;

	//throwing values into pointers
	pCurrent = pHead;
	pNew->m_data = data;
	pNew->m_next = 0;

	//checks for existing list
	if(pHead==0)	{
		//no previous list found
		pHead = pNew;
	} else	{
		//found list adding to tail
		while(pCurrent->m_next)	{
			pCurrent = pCurrent->m_next;
		}
		pCurrent->m_next = pNew; //add the node to the tail
	}

	return;
}

void addHead(sNode*& pHead, int data )	{	
	
	sNode* pNew;				//create new node
	pNew = new(nothrow) sNode;	//assign new node

	pNew->m_data = data;		//add data to new node
	pNew->m_next = pHead;		//add pointer to next node
	pHead = pNew;				//set new head to the newly added node

	return;
}

void f_display(sNode* pCurrent)	{
	if(pCurrent)	{
		cout << pCurrent->m_data << endl;
		f_display(pCurrent->m_next);
	}

	return;
}

void r_display(sNode* pCurrent)	{
	if(pCurrent)	{
		r_display(pCurrent->m_next);
		cout << pCurrent->m_data << endl;
	}

	return;
}