#include <stdio.h>
#include <conio.h>
#define MAX 10

int queue[MAX];
int front=-1;
int rear=-1;
void insert(void);
int delete_element(void);
int peek(void);
void display(void);

int main()
{
	int option, val;
	do
	{
	printf("\n ***** MAIN MENU *****");
	printf("\n 1. Insert an element");
	printf("\n 2. Delete an element");
	printf("\n 3. Peek");
	printf("\n 4. Display the queue");
	printf("\n 5. EXIT");
	printf("\n Enter your option : ");
	scanf("%d", &option);
	switch(option)
	{
		case 1:
			insert();
			break;
		case 2:
			val = delete_element();
			if(val!=-1)
				printf("\n The number deleted is : %d", val);
			break;
		case 3:
			val = peek();
			if(val!=-1)
				printf("\n The first value in queue is : %d", val);
			break;
		case 4:
			display();
			break;
		}
	}while(option!=5);
	getch();
	return 0;
}

void insert()
{
	int num;
	printf("\n Enter the number to be inserted in the queue : ");
	scanf("%d", &num);
	if(front==0 && rear==MAX-1)
		printf("\n OVERFLOW");
	else if(front==-1 && rear==-1)
	{
		front=rear=0;
		queue[rear]=num;
	}
	else if(rear==MAX-1 && front!=0)
	{
		rear=0;
		queue[rear]=num;
	}
	else
	{
		rear++;
		queue[rear]=num;
	}
}

int delete_element()
{
	int val;
	if(front==-1 && rear==-1)
	{
		printf("\n UNDERFLOW");
		return -1;
	}
	val = queue[front];
	if(front==rear)
		front=rear=-1;
	else
	{
		if(front==MAX-1)
			front=0;
		else
			front++;
	}
	return val;
}

int peek()
{
	if(front==-1 && rear==-1)
	{
		printf("\n QUEUE IS EMPTY");
		return -1;
	}
	else
	{
		return queue[front];
	}
}

void display()
{
	int i;
	printf("\n");
	if (front ==-1 && rear==-1)
		printf ("\n QUEUE IS EMPTY");
	else
	{
		if(front<rear)
		{
			for(i=front;i<=rear;i++)
				printf("\t %d", queue[i]);
		}
		else
		{
			for(i=front;i<MAX;i++)
				printf("\t %d", queue[i]);
			for(i=0;i<=rear;i++)
				printf("\t %d", queue[i]);
		}
	}
}