/*
 * Program to learn Queue Data Structure
 *
 * https://www.programiz.com/dsa/queue
 */

#include <stdio.h>


#define SIZE 5

void enQueue(int);
void deQueue();
void display();

int items[SIZE], front = -1, rear = -1;

/* Entry point to program */
int main() 
{
	/* deQueue is not possible on empty queue */
	deQueue();

	/* enQueue 5 elements */
	enQueue(1);
	enQueue(2);
	enQueue(3);
	enQueue(4);
	enQueue(5);

	/* 6th element can't be added to because the queue is full */
	enQueue(6);

	display();

	/* deQueue removes element entered first i.e. 1 */
	deQueue();

	/* Now we have just 4 elements */
	display();
  
	return 0;
}

/* Enqueue Operation */
void enQueue(int value)
{
	if (rear == SIZE - 1)
		printf("\nQueue is Full!!");
	else 
	{
	if (front == -1)
		front = 0;
    
	rear++;
	items[rear] = value;
	printf("\nInserted -> %d", value);
	}
}

/* Dequeue Operation */
void deQueue()
{
	if (front == -1)
		printf("\nQueue is Empty!!");
	else 
	{
		printf("\nDeleted : %d", items[front]);
		front++;
    
		if (front > rear)
			front = rear = -1;
	}
}

/* Function to print the queue */
void display()
{
	int i;
		
	if (rear == -1)
		printf("\nQueue is Empty!!!");
	else
	{
		printf("\nQueue elements are:\n");
		
		for (i = front; i <= rear; i++)
			printf("%d  ", items[i]);
	}
	printf("\n");
}