Insertion and deletion operations on a circular Queue.

circularQueueOperations.c

#include<stdio.h>
#include<stdlib.h>
#define SIZE 15

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


void display()
{
	int i;
	if(front == -1)
	{
		printf("\nEmpty!");
		exit(1);
	}
	else if(front <= rear)
	{
		printf("\nState of the Queue is: \n");
		for(i = front; i <= rear; i++)
		{
			printf("%d\t", Queue[i]);
		}
	}
	else
	{
		printf("\nState of the Queue is: \n");
		
		for(i = front; i <= SIZE-1; i++)
		{
			printf("%d\t", Queue[i]);
		}

		for(i = 0; i <= rear; i++)
		{
			printf("%d\t", Queue[i]);
		}
	}
	
	printf("\n");
}

void insert(int el)
{
	if(front == (rear + 1) % SIZE)
	{
		printf("\nOverflow!\n");
		exit(1);
	}
	else
	{
		if(front == -1 && rear == -1)
		{
			front = 0;
		}
		rear = (rear + 1) % SIZE;
		Queue[rear] = el;
	}
	display();
}

void delete()
{
	int item = Queue[front];
	if(front == -1)
	{
		printf("\nUnderflow!\n");
		exit(1);
	}
	else
	{
		if(front == rear)
		{
			front = rear = -1;
		}
		else
		{
			front = (front + 1) % SIZE;
		}
	}
	printf("\nThe item removed was %d\n", item);
	display();
}

void main()
{
	char option, choice;
	int el;
	do{
		printf("\n\n1.Insert\n2.Delete\n3.Display\nEnter your choice: ");
		option = getchar();
		switch(option)
		{
			case '1':
				printf("\nEnter the element to be inserted: ");
				scanf("%d", &el);
				insert(el);
				break;
			case '2':
				delete();
				break;
			case '3':
				display();
				break;
			default:
				printf("\nInvalid option!");		
		}
	}while(1);
}