#include <stdio.h>
#include <conio.h>
#include <alloc.h>

#define MAX 10

struct dqueue
{
    int arr[MAX] ;
    int front, rear ;
} ;

void initdqueue ( struct dqueue * ) ;
void addqatend ( struct dqueue *, int item ) ;
int delqatbeg ( struct dqueue * ) ;
int delqatend ( struct dqueue * ) ;
void display ( struct dqueue ) ;
int count ( struct dqueue ) ;

void main( )
{
    struct dqueue dq ;
    int i, n ;

    clrscr( ) ;

    initdqueue ( &dq ) ;

    addqatend ( &dq, 11 ) ;
    addqatend ( &dq, 12 ) ;
    addqatend ( &dq, 13 ) ;
    addqatend ( &dq, 14 ) ;
    addqatend ( &dq, 15 ) ;
    addqatend ( &dq, 16 ) ;
    addqatend ( &dq, 17 ) ;
    addqatend ( &dq, 18 ) ;
    addqatend ( &dq, 19 ) ;
    addqatend ( &dq, 20 ) ;

    display ( dq ) ;

    n = count ( dq ) ;
    printf ( "\nTotal elements: %d", n ) ;

    i = delqatbeg ( &dq ) ;
    printf ( "\nItem extracted = %d", i ) ;

    i = delqatbeg ( &dq ) ;
    printf ( "\nItem extracted = %d", i ) ;

    i = delqatend ( &dq ) ;
    printf ( "\nItem extracted = %d", i ) ;

    i =     delqatend ( &dq ) ;
    printf ( "\nItem extracted = %d", i ) ;

    n = count ( dq ) ;
    printf ( "\nElements Left: %d", n ) ;
    display ( dq ) ;

    addqatend ( &dq, 19 ) ;
    addqatend ( &dq, 20 ) ;
    addqatend ( &dq, 21 ) ;
    addqatend ( &dq, 22 ) ;
    addqatend ( &dq, 23 ) ;
    addqatend ( &dq, 24 ) ;

    display ( dq ) ;

    getch( ) ;
}

/* initializes elements of structure */
void initdqueue ( struct dqueue *p )
{
    int i ;

    p -> front = p -> rear = -1 ;

    for ( i = 0 ; i < MAX ; i++ )
        p -> arr[i] = 0 ;
}

/* adds item at the end of dqueue */
void addqatend ( struct dqueue *p, int item )
{
    int i, k ;

    if ( p -> front == 0 && p -> rear == MAX )
    {
       printf ( "\nQueue is full.\n" ) ;
       return ;
    }

    if ( p -> rear == -1 && p -> front == -1 )
    {
        p -> rear = p -> front = 0 ;
        p -> arr[p -> rear] = item ;
        ( p -> rear )++ ;
        return ;
    }

    if ( p -> rear == MAX )
    {
        for ( i = k = p -> front - 1 ; i < p -> rear ; i++ )
        {
            k = i ;
            if ( k == MAX - 1 )
                p -> arr[k] = 0 ;
            else
                p -> arr[k] = p -> arr[i + 1] ;
        }
        ( p -> rear )-- ;
        ( p -> front )-- ;
    }
    p -> arr[p -> rear] = item ;
    ( p -> rear )++ ;
}

/* deletes item from begining of dqueue */
int delqatbeg ( struct dqueue *p )
{
    int item ;

    if ( p -> front == -1 && p -> rear == -1 )
    {
        printf ( "\nQueue is empty.\n" ) ;
        return 0 ;
    }

    item = p -> arr[p -> front] ;
    p -> arr[p -> front] = 0 ;
    ( p -> front )++ ;

    if ( p -> front == MAX )
        p -> front = -1 ;

    return item ;
}

/* deletes item from end of dqueue */
int delqatend ( struct dqueue *p )
{
    int item ;

    if ( p -> front == -1 && p -> rear == -1 )
    {
        printf ( "\nQueue is empty.\n" ) ;
        return 0 ;
    }

    ( p -> rear )-- ;
    item = p -> arr[p -> rear] ;
    p -> arr[p -> rear] = 0 ;

    if ( p -> rear == 0 )
        p -> rear = -1 ;
    return item ;
}

/* displays the queue */
void display ( struct dqueue dq )
{
    int i ;

    printf ( "\n front -> " ) ;

    for ( i = 0 ; i < MAX ; i++ )
        printf ( "%d\t", dq.arr[i] ) ;
    printf ( " <- rear" ) ;
}

/* counts the number of items in dqueue */
int count ( struct dqueue dq )
{
    int c, i ;

    for ( i = c = 0 ; i < MAX ; i++ )
    {
        if ( dq.arr[i] != 0 )
            c++ ;
    }
    return c ;
}