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 number of elements in the list that are equal to value
  int subCountEqual(int value, Node* subHead) const;
  
  // sub method to insert the given value after each even value
  void subInsertAfterEvens(int value, Node* subHead);
  
  // sub method to return true if the two lists are the same length, false otherwise
  bool subIsSameLengthAs(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 number of elements in the list that are equal to value
  int countEqual(int value) const;
  
  // inserts the given value after each even value
  void insertAfterEvens(int value);
  
  // returns true if the two lists are the same length, false otherwise
  bool isSameLengthAs(const List &otherList) const;

};