//------------------- queue2.cpp -------------------------
//------------ source file for unit queue ----------------

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include "queue2.h"


//--------------------------- Iplementstion -----------------------------

//--------- queue_init -------------------------

queue_type queue_init (void)
{
	queue_type Q;

	Q.front = Q.rear = NULL ;
	return (Q) ;
}

//--------- queue_insert (Q, x) ----------------

void queue_insert (queue_type &Q, queue_info_type x)
{
	pos_type p;

	p = (pos_type)malloc(sizeof(struct link_type));
	p->info = x;
	p->next = NULL ;
	if (Q.front == NULL)
		Q.front = p ;
	else
		Q.rear->next = p;
	Q.rear = p ;
}

//----------- queue_remove (Q) ---------------------
//        assumption: Q is not empty

queue_info_type queue_remove (queue_type &Q)
{
	pos_type p ;
	queue_info_type x ;

	p = Q.front ;
	Q.front = Q.front->next ;
	if (Q.front == NULL)
		Q.rear = NULL ;

	x = p->info ;
	free (p) ;

	return (x) ;
}

//------------ queue_top (Q) ----------------------

queue_info_type queue_top (queue_type Q)
{
	return (Q.front->info) ;
}

//-------------------- queue_empty (Q) --------------------

int queue_empty (queue_type Q)
{
	return (Q.front == NULL) ;     // Q.front == Q.rear == NULL;
}

//-------------------- queue_show (Q) ---------------------

void queue_show (queue_type Q)
{
	queue_type Q1 ;
	queue_info_type x ;

	Q1 = queue_init () ;

	printf ("Front --> ") ;
	while (! queue_empty (Q))
	{
		x = queue_remove (Q) ;
		printf("%d   ",x);
		queue_insert (Q1, x) ;
	}

	while (! queue_empty (Q1))
	{
		x = queue_remove (Q1) ;
		queue_insert (Q, x) ;
	}
	printf (" Rear \n \n") ;
}