#include<iostream>
using namespace std;
#define SIZE 20
class dequeue 
{
   int a[20],f,r;
   public:
      dequeue();
      void insert_at_beg(int);
      void insert_at_end(int);
      void delete_fr_front();
      void delete_fr_rear();
      void show();
};

dequeue::dequeue() 
{
   f=-1;
   r=-1;
}

void dequeue::insert_at_end(int i)
 {
   if(r>=SIZE-1) 
      cout<<"insertion is not possible, overflow!!!!";
    else
    {
      if(f==-1)
      {
         f++;
         r++;
      } 
      else 
         r=r+1;
      a[r]=i;
      cout<<"Inserted item is"<<a[r];
   }
}

void dequeue::insert_at_beg(int i) {
   if(f==-1) {
      f=0;
      a[++r]=i;
      cout<<" inserted element is:"<<i;
   } 
    else if(f!=0)
    {
      a[--f]=i;
      cout<<" inserted element is:"<<i;
   } 
   else {
      cout<<" insertion is not possible, overflow!!!";
   }
}
void dequeue::delete_fr_front() {
   if(f==-1) {
      cout<<"deletion is not possible::dequeue is empty";
      return;
   }
   else {
      cout<<"the deleted element is:"<<a[f];
      if(f==r) {
         f=r=-1;
         return;
      } else
         f=f+1;
      }
   }
   void dequeue::delete_fr_rear() {
      if(f==-1) {
         cout<<"deletion is not possible::dequeue is empty";
         return;
      }
      else {
         cout<<"the deleted element is:"<<a[r];
         if(f==r) {
            f=r=-1;
         } else
            r=r-1;
      }
   }
   void dequeue::show() {
      if(f==-1) {
         cout<<"Dequeue is empty";
      } else {
         for(int i=f;i<=r;i++) {
            cout<<a[i]<<" ";
         }
      }
   }

int main() 
{
      int c,i;
      dequeue d;
      do//perform switch opeartion 
      {
      cout<<" 1.insert at beginning";
      cout<<" 2.insert at end";
      cout<<" 3.show";
      cout<<" 4.deletion from front";
      cout<<" 5.deletion from rear";
      cout<<" 6.exit";
      cout<<" enter your choice:";
      cin>>c;
      switch(c)
	 {
         case 1:
            cout<<"enter the element to be inserted";
            cin>>i;
            d.insert_at_beg(i);
         break;
         case 2:
            cout<<"enter the element to be inserted";
            cin>>i;
            d.insert_at_end(i);
         break;
         case 3:
            d.show();
            break;
         case 4:
            d.delete_fr_front();
            break;
         case 5:
            d.delete_fr_rear();
            break;
         default:
            cout<<"invalid choice";
            break;
      }
   }while(c!=7);
return 0;
}