class List {
private:

  class Node {
  public:
    int data;
    Node * next;
    Node (int data, Node *next) {
      Node::data = data; Node::next = next;
    }
  };

  Node *head;

  // Utility method to delete all elements of a list.  
  void deleteList();

  // Utility method to copy from one list to another.  
  void copyFrom (const List &otherList);
  
  // sub method to return the sum of all values in the list that are greater than value
  int subSumMoreThan(int value, Node* subHead) const;
  
  // sub method to duplicate all even values in the list
  void subDuplicateEvens(Node* subHead);
  
  // sub method to return true if the list is shorter than the other list, false otherwise
  bool subIsShorterThan(Node* subHead, Node* otherSubHead) const;

public:

  List () { head = NULL; };

  List(const List &otherList); // copy constructor

  ~List ();

  // outputs list contents to cout
  void outputList () const;

  // adds a value to the list
  void insert (int value);

  List& operator=(const List &otherList); // operator=
  
  // returns the sum of all values in the list that are greater than value
  int sumMoreThan(int value) const;
  
  // duplicates all even values in the list
  void duplicateEvens();
  
  // returns true if the list is shorter than the other list, false otherwise
  bool isShorterThan(const List &otherList) const;

};