Input-restricted deque program using array

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

In an input restricted deque the insertion of elements is at one end only, but the deletion of elements can be done at both the ends of a queue. Write a program that demonstrates an input-restricted dque.

#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 ;
}