//CIS 610: Lists
//Syed Rais Ahmad
//Assignment # 5 Question 4.

#include<iostream.h>

class llistItem
{
public:
	int item;
	llistItem * nxtItem;
};



class lList
{
private:
	llistItem * head;
public:
	lList(); 
	~lList() {delete head;}; 
	void add(int addInt);
	void getall();
	void swap(int,int);

};


//Init
lList::lList()
{
	head = new llistItem; 
	head->nxtItem=NULL;
	head->item=NULL;
}


//add to the tail of link list
void lList::add(int addInt)
{
	llistItem * ptr=head; //a temporary listitem pointer holds head address of link list.

	while(ptr->nxtItem) 
		ptr=ptr->nxtItem; //reach the item whose nextitem points to NULL address

	ptr->nxtItem=new llistItem; //add a new list item
	ptr=ptr->nxtItem; // temporary pointer holds new item's address
	ptr->item=addInt; // add a value to new item
	ptr->nxtItem=NULL; //make next item of new item point to NULL
}


//print all items in the link list.
void lList::getall()
{
	llistItem * ptr=head; //ptr gets the head value
		while (ptr=(ptr->nxtItem)) //while ptr points to not NULL value
			cout << ptr->item << "\n";

	
}

void lList::swap(int m,int n)
{

	int i=0,first,sec;llistItem * ptr, * temp;
	ptr=head;
	if (m!=n)
	{
//while traversing list, first will be encountered first
		first=(m>n)? n: m; 
		sec=(first==m)? n : m;
//traverse the list to first item. Store its address and value
		while(i++<first && ptr->nxtItem) ptr=ptr->nxtItem;
		temp=ptr;
		first=ptr->item;
		i--;
//traverse to second item. Swap the values now.
		while(i++<sec && ptr->nxtItem) ptr=ptr->nxtItem;
		sec=ptr->item;
		ptr->item=first;
		temp->item=sec;
	}

}



//------- Program's main flow starts ---------------------------


main()
{
	lList l;

	l.add(9);
	l.add(4);
	l.add(5);
	l.add(6);
	l.add(74);
	l.add(84);
	cout << "\nItems in List are:\n";
	l.getall();
	
	cout << "\nSwap items 3rd and 5th:\n";
	l.swap(3,5);

	cout << "\nItems in List are:\n";
	l.getall();
	
	return 0;
}