queue_linklist.cpp

Implementation of a queue using a Linklist.

#include<iostream.h>
#include<alloc.h>
#include<stdlib.h>
//using namespace std;
class queue
{
    private:
    int data;
    public:
    queue *next;
    void append(queue **,queue **,int);
    void del(queue **,queue **);
    int display(queue *);
};
void queue::append(queue **f,queue **r,int i)
    {
        queue *temp=(queue *)malloc(sizeof(queue));
        temp->data=i;
        temp->next=NULL;
        if(*f==NULL)//starting node
	    *f=*r=temp;
        else
        {
            (*r)->next=temp;
            *r=temp;
        }
    cout<<"\nItem appended!!"<<endl;
    }
void queue::del(queue **f,queue **r)
    {
        int item;queue *temp;
	if(*f==NULL && *r==NULL)
            cout<<"\nQueue Empty!!"<<endl;
        else//delete node at beginning
            {
                cout<<"\nItem deleted is :"<<(*f)->data<<endl;
                if(*f==*r)//only one node
                    {
                        free(*f);
                        *f=*r=NULL;
                    }
                else
                {
                    temp=(*f)->next;
                    free(*f);
                    *f=temp;
                }
            }
    }
int queue::display(queue *f)
    {
        int c=0;
        if(f==NULL)
        {
        cout<<"\nQueue Empty!!";
        return c;
        }
        else
        while(f!=NULL)
            {
                cout<<f->data<<"  ";c++;
                f=f->next;
            }
    return c;
    }
int main()
{
    int ch,item;
    queue q;
    queue *front=NULL,*rear=NULL;
    do
    {
    cout<<"\nMENU\n1.append\n2.delete\n3.display\n4.exit\nEnter your choice :";
    cin>>ch;
    switch(ch)
        {
            case 1:
            cout<<"\nEnter the item to append :";
            cin>>item;
            q.append(&front,&rear,item);
            break;
            case 2:
            q.del(&front,&rear);
            break;
            case 3:
            cout<<"\nNo. of elements in queue is :"<<q.display(front)<<endl;
            break;
            case 4:
            exit(0);
        }
    }while(ch!=4);
    return 0;
}