帮助双链表？

class Node {
public:
Node() { next = NULL; prev = NULL; }
~Node() {}
public :
Node *next;
Node *prev;
T data;


 };

 public:
LinkedList();
~LinkedList();

// methods -- note that the return values are of type T. Don\'t return a Node!
  void append(T item);
  T get(int idx);
  void insert(int idx, T item);
  void map(T (*pf)(T item));
  T remove(int index);
  int size();
  void unshift(T item);

LinkedList<T>::LinkedList() {

head = NULL;
current = NULL;

}

LinkedList<T>::LinkedList() {
    head = NULL;
    current = NULL;
}