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iterator class for list and vector

firix (438)
Hi,

I've written the source code vector and list.
I would like to write the iterator class for these classes 

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template <class T  class  Itor{ // common interface (abstract class)
public:
virtual T * first() = 0 ; // pointer to first element
virtual T * next() = 0 ; // pointer to next element
};

How do I write this class
How I write the iterator class for list and vector?

list and vector 


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template<class T>
class List{
public:
	struct node{
	T  val;
	node *pnext;
	node *prev;
	node()
	{	
		pnext = 0;
		prev = 0;
	}
    };
   
	node *phead;
	node *ptail;
	size_t count;
public:
    List<T>()
    { 
       phead = 0;
	   ptail = 0;
	   count = 0;

    }

    node *push_front(T val)
	{
		node *pnewnode = new node;
		pnewnode->val  = val;
		pnewnode->pnext = phead;
		phead = pnewnode;

		if (ptail == 0)
			ptail =  pnewnode;

		count++;

		return pnewnode;

	}
    node *push_back(T val)
	{
		node *pnewnode = new node;
		pnewnode->val = val;
		pnewnode->pnext = 0;

		if (phead != 0)
			ptail->pnext = pnewnode;
		else
			phead = pnewnode;
		ptail = pnewnode;

		count++; 
        return pnewnode;
	}

    node *Insert(node *pNode, T val)
	{
		node *pnewnode = new node;
		pnewnode->val = val;

		pnewnode->pnext = pNode->pnext;
		pNode->pnext = pnewnode;
		pnewnode->prev = pNode;
		pnewnode->pnext->prev = pnewnode;

		if (ptail == pNode)
			ptail = pnewnode;
		count++;
		return pnewnode;
	}

	node *InsertNodeIndex(size_t index, T val)
	{
		node *pnode;


		if (index == 0) {
			return AddNodeHead(val);
		}
	
		
		pnode = phead;
		for (int i  = 0; i < index -1; ++i) 
			pnode = pnode->pnext;

		return Insert(pnode, val);

	}

	void Delete(node *pNode)
	{
		node *ptemp;
		ptemp = pNode->pnext;

		if (ptemp == ptail)
			ptail = pNode;
		pNode->pnext = ptemp->pnext;
		--count;
		delete ptemp;

	}


	bool DeleteNodeIndex(size_t index)
	{
		node *pnode;
		node *ptemp;

		if (index >= count){
			return false;

		if (index == 0)
			ptemp = phead;
		if (count == 1)
			ptail = 0;
		phead = ptemp->pnext;
		delete ptemp;
		--count;
		return true;
		}

		pnode = phead;
		for (int i= 0; i < index -1; ++i)
			pnode = pnode->pnext;
		Delete(pnode);

		return true;

	}

     void print()
	{
		node *p = phead;
		if (p == 0)
			cout << "Empty\n" << endl;
		int n = count;
		while(n--) {
			cout << p->val << endl;
		p = p->pnext;
		}	
	}};



thanks in advance.
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