queue.c

/*
C Program for implementing Queue using Array
Author: Vivek K J
S3 CSA
*/


#include<stdio.h>
#include<stdlib.h>
#define MAX_SIZE 3
// Global variables
int queue[MAX_SIZE], REAR=-1, FRONT=-1;
// Function to Enqueue
void enqueue(){
	int item;
	if(REAR==MAX_SIZE-1){
		printf("Queue is Full");
	}else{
		printf("Enter the item to be pushed:");			
		scanf("%d", &item);
		if(REAR==-1 && FRONT==-1){
			REAR=0;
			FRONT=0;
			queue[REAR]=item;
		}
		else{
			REAR=REAR+1;
			queue[REAR]=item;
		}
	}

}
// Function to Dequeue
void dequeue(){
	int item;
	if(REAR==-1 && FRONT==-1){
		printf("Queue is empty");
	}
	else{
		if(REAR==FRONT){
			item = queue[FRONT];
			printf("Item Deleted is %d", item);
			FRONT=-1;
			REAR=-1;
		}else{
			item = queue[FRONT];
			printf("Item Deleted is %d", item);
			FRONT+= 1;
		}
	}
}
// Function to display
void display(){
	if(FRONT==-1 && REAR==-1){
		printf("Queue is Empty");
	}else{
		for(int i=FRONT; i<=REAR; i++){
			printf("%d \t", queue[i]);
		}
	}
}
// Main function
void main(){
	while(1){
	int n;
	printf("\n 1. Enqueue\n 2. Dequeue\n 3. Display\n 4. Exit\n");
	printf("Enter your choice:");
	scanf("%d", &n);
	switch(n){
		case 1: 
			enqueue();
			break;
		case 2:
			dequeue();
			break;
		case 3:
			display();
			break;
		case 4:
			exit(0);
			break;
		default:
			printf("Enter a valid choice");
	

	}
	 }
}