A deque is a data structure that allows both deletion as well as insertion of elements to be done at both ends of a queue. 

Implement a deque using a circular array.

#define N 10
#include<stdio.h>
#include<stdlib.h>

typedef int element;
typedef struct 
{
	element  data[N];
    	int  front;
    	int  rear;
} Deque;
	

Deque CreateDeque()
{
	Deque q;
	q.front = 1; q.rear=0;
	return q;
}

int isFullDeque(Deque q)
{
	return (q.front == (q.rear+2)%N);
}

int isEmptyDeque(Deque q)
{
	return (q.front == (q.rear+1)%N);
}

int insertFront(Deque *q, element e)
{
    	if(isFullDeque(*q))  return 0;
 
    	q->front = (q->front-1+N)%N;

    	q->data[q->front] = e ;
	return 1;
}

int insertRear(Deque *q, element e)
{
    	if(isFullDeque(*q))  return 0;
 
    	q->rear = (q->rear+1)%N;
	
    	q->data[q->rear] = e ;
	return 1;
}


int deleteFront(Deque *q)
{
	if (isEmptyDeque(*q)) return 0;
 
    q->front = (q->front+1)%N;
	return 1;
}

int deleteRear(Deque *q)
{
	if (isEmptyDeque(*q)) return 0;
 
	q->rear = (q->rear-1+N)%N;
	return 1;
}

int Front(Deque q, element *e)
{
	if (isEmptyDeque(q)) return 0;
	*e = q.data[q.front];
	return 1;
}


int Rear(Deque q, element *e)
{
	if (isEmptyDeque(q) ) return 0;
	*e = q.data[q.rear];
	return 1;
}

void print(Deque d)
{
    	element e;
    	printf("FRONT --> ");
    	while(Front(d,&e))
    	{
        	deleteFront(&d);
        	printf("%d  ",e);
    	}
    	printf("<-- REAR\n\n");
}


void test1()
{
	Deque d ;
	element e;
	int i;

	d=CreateDeque();

    	for(i=10;i<=30;i+=2)
    	{
        	insertFront(&d,i);
        	insertRear(&d,i+1);
        	print(d);
    	}
    
    	
    
    	for(i=10;i<=30;i+=2)
    	{
        	deleteFront(&d);
        	deleteRear(&d);
        	print(d);
    	}
}

int main()
{
	test1();
	return 0;
}