// Textbook fragment 10.03
// Realization of a dictionary by means of a binary search tree
public class BinarySearchTree<K,V>
  extends LinkedBinaryTree<Entry<K,V>> implements Dictionary<K,V> {
  protected Comparator<K> C;    // comparator
  protected Position<Entry<K,V>>
              actionPos; // insert node or removed node's parent
  protected int numEntries = 0; // number of entries
  /** Creates a BinarySearchTree with a default comparator. */
  public BinarySearchTree()  {
    C = new DefaultComparator<K>();
    addRoot(null);
  }
  public BinarySearchTree(Comparator<K> c)  {
    C = c;
    addRoot(null);
  }
  /** Nested class for location-aware binary search tree entries */
  protected static class BSTEntry<K,V> implements Entry<K,V> {
    protected K key;
    protected V value;
    protected Position<Entry<K,V>> pos;
    BSTEntry() { /* default constructor */ }
    BSTEntry(K k, V v, Position<Entry<K,V>> p) {
      key = k; value = v; pos = p;
    }
    public K getKey() { return key; }
    public V getValue() { return value; }
    public Position<Entry<K,V>> position() { return pos; }
  }
  /** Extracts the key of the entry at a given node of the tree. */
  protected K key(Position<Entry<K,V>> position)  {
    return position.element().getKey();
  }
  /** Extracts the value of the entry at a given node of the tree. */
  protected V value(Position<Entry<K,V>> position)  {
    return position.element().getValue();
  }
  /** Extracts the entry at a given node of the tree. */
  protected Entry<K,V> entry(Position<Entry<K,V>> position)  {
    return position.element();
  }
  /** Replaces an entry with a new entry (and reset the entry's location) */
  protected void replaceEntry(Position <Entry<K,V>> pos, Entry<K,V> ent) {
    ((BSTEntry<K,V>) ent).pos = pos;
    replace(pos, ent);
  }