#include <iostream>

struct node
{
	node	*next = { nullptr };
	node	*prev = { nullptr };
	int		value;

	node(int i=0)
	{
		value = i;
	}
};

static void print_list(node *phead, node *ptail)
{
	std::cout << "************ list **************" << std::endl;
	std::cout << "head: " << phead << std::endl;
	std::cout << "tail: " << ptail << std::endl;

	while(phead)
	{
		std::cout << "node: " << phead << std::endl;		// print the address of the node
		std::cout << "   next=" << phead->next << std::endl;
		std::cout << "   prev=" << phead->prev << std::endl;
		std::cout << "  value=" << phead->value << std::endl;

		phead = phead->next;	// prepare to print the 'next' node
	}
}


int main()
{
	node *phead = nullptr;
	node *ptail = nullptr;

	print_list(phead, ptail);

	// insert a new node into an empty list
	node *pn1 = new node(1);
	phead = pn1;		// the new node is both the head 
	ptail = pn1;		// ...and tail node

	print_list(phead, ptail);

	// insert a new node at the head of a non-empty list
	node *pn2 = new node(2);
	pn2->next = phead;	// link the new node to node #1
	phead->prev = pn2;	// link from the prior head node #1 back to this new one
	phead = pn2;		// the new node #2 is the new head of the list

	print_list(phead, ptail);

	// insert a new node at the tail of a non-empty list
	node *pn3 = new node(3);
	pn3->prev = ptail;	// point backwards to the previous tail node
	ptail->next = pn3;	// link from the prior tail node #1 foreward to this new one
	ptail = pn3;

	print_list(phead, ptail);

	// insert a new node into the middle of the list after node #1
	node *pn4 = new node(4);
	pn4->prev = pn1;		// connect to new node to neighboring nodes
	pn4->next = pn1->next;
	pn4->prev->next = pn4;	// connect neighbors to the new node
	pn4->next->prev = pn4;

	print_list(phead, ptail);

	return 0;
}




#if 0
// generic node insert logic:

	pn = new node(2);
	if (phead)
	{
		pn->next = phead;	// link the new node to node #1
		phead->prev = pn;	// link from node #1 back to this new node #2
	}
	else	// list was empty!
	{
		ptail = pn;
	}
	phead = pn;				// the new node #2 is the new head of the list

#endif