Queue_using_Array.c

// Operatins on Queue using array

#include<stdio.h>
#include<stdlib.h>
#define MAX 5
void enqueue(int);
void dqueue(int*);
void display();

struct QUEUE
{
	int s[MAX];
	int r,f;
}stk;

void main()
{
	int i,a;
	stk.r=stk.f=-1;
	while(1)
	{
		printf("\n 1.Enter");
		printf("\n 2.Delete");
		printf("\n 3.Display");
		printf("\n 4.Exit");
		printf("\n Enter your choice between 1 to 4:  ");
		scanf("%d",&i);
		switch(i)
		{
			case 1: printf("Enter the item to push in queue\n");
				scanf("%d",&a);
				enqueue(a);break;
			case 2: dqueue(&a);
				if(a!=-999)
				printf("%d is Deleted\n",a);
				break;
			case 3: display();break;
			case 4: exit(0);
			default:printf("Please enter a choice in between 1 to 5");
		}
	}
}

void enqueue(int a)
{
	if(stk.r == MAX-1)
	{
		printf("Queue is full \n");
		return;
	}
	else
	{
		stk.s[++stk.r]=a;
		return;
	}
}

void dqueue(int *a)
{
	if(stk.f==stk.r)
	{
		stk.f=stk.r=-1;
		printf("Queue is empty \n");
		*a=-999;
		return;
	}
	else
	{
		*a=stk.s[++stk.f];
		return;
	}
}
void display()
{
	int i;
	if(stk.f==stk.r)
	{
		stk.f=stk.r=-1;
		printf("Queue is empty \n");
		return;
	}
	
	for (i=stk.f+1;i<=stk.r;i++)
		printf("%d",stk.s[i]);
	printf("\n");return;
}