Output-restricted deque program using array

/* Output-restricted deque program using array. */

In an output restricted deque, the deletion of elements is done at one end only, and allows insertion to be done at both the ends of a deque. Write a program to demonstrate output-restricted deque.

#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 addqatbeg ( struct dqueue *, int ) ;
void addqatend ( struct dqueue *, int ) ;
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 ) ;
addqatbeg ( &dq, 10 ) ;
addqatend ( &dq, 12 ) ;
addqatbeg ( &dq, 9 ) ;
addqatend ( &dq, 13 ) ;
addqatbeg ( &dq, 8 ) ;
addqatend ( &dq, 14 ) ;
addqatbeg ( &dq, 7 ) ;
addqatend ( &dq, 15 ) ;
addqatbeg ( &dq, 6 ) ;
addqatend ( &dq, 16 ) ;
addqatbeg ( &dq, 5 ) ;

display ( dq ) ;

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

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

i = delqatend ( &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 ) ;

addqatbeg ( &dq, 5 ) ;
addqatbeg ( &dq, 4 ) ;
addqatbeg ( &dq, 3 ) ;
addqatbeg ( &dq, 2 ) ;

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 begining of dqueue */
void addqatbeg ( struct dqueue *p, int item )
{
int c, i, k ;

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

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

if ( p -> rear != MAX )
{
c = count ( *p ) ;
k = p -> rear ;

for ( i = 1 ; i <= c ; i++ )
{
p -> arr[k] = p -> arr[k - 1] ;
k-- ;
}

p -> arr[k] = item ;
p -> front = k ;
( p -> rear )++ ;
}
else
{
( p -> front )-- ;
p -> arr[p -> front] = item ;
}
}

/* 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 )
{
k = p -> front - 1 ;

for ( i = 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 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 ( "\t%d", 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 ;
}