#ifndef LL_HPP#define LL_HPP#ifndef NULL#define NULL 0#endif#include <fstream.h>class node;class node  {  public:    int number;    node *next, *prev;    node(int num) {number=num;}    node() {number=-1;}  };class LL  {  protected:  node headdummy,taildummy;  // dummy nodes for the ends of the ll  //unsigned int length;       // holds length of ll  node* head;                // ptr to head of ll  node* tail;                // ptr to tail of ll  unsigned int curcount;     // keeps track of where current is pointing  public:  node* current;             // ptr to current point of ll  LL(void);                  // constructor  void addhead(node* nnode); // adds nnode to head of ll  void addtail(node* nnode); // adds nnode to tail of ll  node* removehead(void);    // removes head of ll, returns ptr to it  node* removetail(void);    // removes tail of ll, returns ptr to it  void removenode(node* nnode); // removes nnode from the ll  node* get(int index);      // returns ptr to index number from head  void reset(void);          // resets current to head  void operator++();         // increments current  int search(node* nnode);   // search if nnode is in list, return index  unsigned int length;  };#endif