DSPS Practical : Doubly Circular Linked List (DCLL)

#include<iostream>
#include<cstdio>
#include<cstdlib>
using namespace std;
struct node
{
   int info;
   struct node *next;
   struct node *prev;
}*start, *last;

int counter = 0;
class dcll
{
 public:
        node *create_node(int);
        void insert_begin();
        void insert_last();
        void insert_pos();
        void delete_pos();
        void search();
        void update();
        void display();
        void reverse();
        dcll()
        {
          start = NULL;
          last = NULL;
        }
    };

    node* dcll::create_node(int value)

    {
       counter++;
       struct node *temp;
       temp = new(struct node);
       temp->info = value;
       temp->next = NULL;
       temp->prev = NULL;
       return temp;
    }


    void dcll::insert_begin()
    {

        int value;
        cout<<endl<<"Enter the element to be inserted: ";
        cin>>value;
        struct node *temp;
        temp = create_node(value);
        if (start == last && start == NULL)
        {
            cout<<"Element inserted in empty list"<<endl;
            start = last = temp;
            start->next = last->next = NULL;
            start->prev = last->prev = NULL;
        }
        else
        {
            temp->next = start;
            start->prev = temp;
            start = temp;
            start->prev = last;
            last->next = start;
            cout<<"Element inserted"<<endl;
        }
    }
    void dcll::insert_last()
    {
        int value;
        cout<<endl<<"Enter the element to be inserted: ";
        cin>>value;
        struct node *temp;
        temp = create_node(value);
        if (start == last && start == NULL)
        {
           cout<<"Element inserted in empty list"<<endl;
            start = last = temp;
            start->next = last->next = NULL;
            start->prev = last->prev = NULL;
        }
        else
        {
            last->next = temp;
           temp->prev = last;
            last = temp;
            start->prev = last;
            last->next = start;
        }
    }
    void dcll::insert_pos()
    {
        int value, pos, i;
        cout<<endl<<"Enter the element to be inserted: ";
        cin>>value;
        cout<<endl<<"Enter the postion of element inserted: ";
        cin>>pos;
        struct node *temp, *s, *ptr;
        temp = create_node(value);
        if (start == last && start == NULL)
        {
            if (pos == 1)
            {
                start = last = temp;
                start->next = last->next = NULL;
                start->prev = last->prev = NULL;
           }
            else
            {
                cout<<"Position out of range"<<endl;
                counter--;
                return;
            }
        }
        else
        {
            if (counter < pos)
            {
                 cout<<"Position out of range"<<endl;
                 counter--;
                 return;
            }
            s = start;
            for (i = 1;i <= counter;i++)
            {
                ptr = s;
               s = s->next;
                if (i == pos - 1)
                {
                    ptr->next = temp;
                    temp->prev = ptr;
                    temp->next = s;
                    s->prev = temp;
                    cout<<"Element inserted"<<endl;
                   break;
                }
            }
        }
    }
    void dcll::delete_pos()
    {
        int pos, i;
        node *ptr, *s;
        if (start == last && start == NULL)
        {
            cout<<"List is empty, nothing to delete"<<endl;
            return;
        }
        cout<<endl<<"Enter the postion of element to be deleted: ";
        cin>>pos;
        if (counter < pos)
        {
            cout<<"Position out of range"<<endl;
            return;
        }
        s = start;
        if(pos == 1)
        {
            counter--;
            last->next = s->next;
            s->next->prev = last;
            start = s->next;
            free(s);
            cout<<"Element Deleted"<<endl;
            return;
        }
        for (i = 0;i < pos - 1;i++ )
        {
            s = s->next;
            ptr = s->prev;
        }
        ptr->next = s->next;
        s->next->prev = ptr;
        if (pos == counter)
        {
            last = ptr;
        }
        counter--;
        free(s);
        cout<<"Element Deleted"<<endl;

    }

    void dcll::update()
    {
        int value, i, pos;
        if (start == last && start == NULL)
        {
            cout<<"The List is empty, nothing to update"<<endl;
            return;
        }
        cout<<endl<<"Enter the postion of node to be updated: ";
        cin>>pos;
        cout<<"Enter the new value: ";
        cin>>value;
        struct node *s;
        if (counter < pos)
        {
            cout<<"Position out of range"<<endl;
            return;
        }
        s = start;
        if (pos == 1)
        {
           s->info = value;
           cout<<"Node Updated"<<endl;
           return;
        }
        for (i=0;i < pos - 1;i++)
        {
            s = s->next;
        }
        s->info = value;
        cout<<"Node Updated"<<endl;
    }
 void dcll::search()
 {
       int pos = 0, value, i;
        bool flag = false;
        struct node *s;
        if (start == last && start == NULL)
        {
            cout<<"The List is empty, nothing to search"<<endl;
            return;
        }
        cout<<endl<<"Enter the value to be searched: ";
        cin>>value;
        s = start;
        for (i = 0;i < counter;i++)
        {
            pos++;
            if (s->info == value)
            {
                cout<<"Element "<<value<<" found at position: "<<pos<<endl;
               flag = true;
            }
            s = s->next;
        }
        if (!flag){
            cout<<"Element not found in the list"<<endl;
    }
 }
 void dcll::display()
  {
        int i;
        struct node *s;
        if (start == last && start == NULL)
        {
            cout<<"The List is empty, nothing to display"<<endl;
            return;
        }
        s = start;
        for (i = 0;i < counter-1;i++)
        {
            cout<<s->info<<"<->";
            s = s->next;
        }
        cout<<s->info<<endl;
    }
void dcll::reverse()
{
     if (start == last && start == NULL)
        {
            cout<<"The List is empty, nothing to reverse"<<endl;
            return;
        }
        struct node *p1, *p2;
        p1 = start;
        p2 = p1->next;
        p1->next = NULL;
        p1->prev = p2;
        while (p2 != start)
        {
            p2->prev = p2->next;
            p2->next = p1;
            p1 = p2;
            p2 = p2->prev;
        }
        last = start;
        start = p1;
        cout<<"List Reversed"<<endl;

 }
int main()
{
  int c;
  dcll dc;
while (1)
{
cout<<"---------MENU---------------"<<endl;
cout<<"1.Insert at Beginning"<<endl;
cout<<"2.Insert at Last"<<endl;
cout<<"3.Insert at Position"<<endl;
cout<<"4.Delete at Position"<<endl;
cout<<"5.Update"<<endl;
cout<<"6.Search Element"<<endl;
cout<<"7.Display List"<<endl;
cout<<"8.Reverse List"<<endl;
cout<<"9.Exit"<<endl;

cout<<"Enter your choice : ";
cin>>c;
switch(c)
{
  case 1: dc.insert_begin(); dc.display();break;
  case 2: dc.insert_last();  dc.display();break;
  case 3: dc.insert_pos();   dc.display();break;
  case 4: dc.delete_pos();   dc.display();break;
  case 5: dc.update();       dc.display();break;
  case 6: dc.search();                   break;
  case 7: dc.display();                  break;
  case 8: dc.reverse();      dc.display();break;
  case 9: exit(1);
  default: cout<<"Please try again"<<endl;}
}
return 0;
}

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