Queue :- Queue is a linear data structure in which  insertion of new element take place at one end known as Rear or Back end and deletion of existing element takes place at the other end known as Front end.


Queues are sometimes also called  FIFO List (First-In-First-Out).




#include<iostream.h>
#include<conio.h>
struct node
{
      int data;
      node *next;
};
class queue
{
      node *rear,*front;
public:
      queue()
      { rear=NULL;front=NULL;}
      void qinsert();
      void qdelete();
      void qdisplay();
      ~queue();
};
void queue::qinsert()
{
      node *temp;
      temp=new node;
      cout<<"Data :";
      cin>>temp->data;
      temp->next=NULL;
      if(rear==NULL)
      {
            rear=temp;
            front=temp;
      }
      else
      {
            rear->next=temp;
            rear=temp;
      }
}
void queue::qdelete()
{
      if(front!=NULL)
      {
            node *temp=front;
            cout<<front->data<<"deleted \n";
            front=front->next;
            delete temp;
            if(front==NULL)
                  rear=NULL;
      }
      else
            cout<<"Queue Empty..";
}
void queue::qdisplay()
{
      node *temp=front;
      while(temp!=NULL)
      {
            cout<<temp->data<<endl;
            temp=temp->next;
      }
}
queue::~queue()
{
      while(front!=NULL)
      {
            node *temp=front;
            front=front->next;
            delete temp;
      }
}
void main()
{
      queue obj; char ch;
      do
      {
            cout<< "i. insert\nd. Delete\ns. Display\n q. quit ";
            cin>>ch;
            switch(ch)
            {
                  case 'i' : obj.qinsert();break;
                  case 'd' : obj.qdelete();break;
                  case 's' : obj.qdisplay();
            }
      }while(ch!='q');
}