unisa_strutture_dati_2013_2014/dictionary/BinarySearchTree.java

package dictionary;
import exceptions.InvalidEntryException;
import exceptions.InvalidKeyException;
import position.NodePositionList;
import position.Position;
import position.PositionList;
import priorityqueue.Entry;
import tree.binarytree.BTPosition;
import tree.binarytree.LinkedBinaryTree;
import utility.DefaultComparator;


import java.util.Comparator;




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

  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(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);
  }


protected void checkKey(K key) throws InvalidKeyException {
  if(key == null)
    throw new InvalidKeyException("null key");
}

protected void checkEntry(Entry<K,V> ent) throws InvalidEntryException {
  if(ent == null || !(ent instanceof BSTEntry))
    throw new InvalidEntryException("invalid entry");
}

protected Entry<K,V> insertAtExternal(Position<Entry<K,V>> v, Entry<K,V> e) {
  expandExternal(v,null,null);
  replace(v, e);
  numEntries++;
  return e;
}
/** Auxiliary method for removing an external node and its parent */
protected void removeExternal(Position<Entry<K,V>> v) {
  removeAboveExternal(v);
  numEntries--;
}
/** Auxiliary method used by find, insert, and remove. */
protected Position<Entry<K,V>> treeSearch(K key, Position<Entry<K,V>> pos) {
  if (isExternal(pos)) return pos; // key not found; return external node
  else {
    K curKey = key(pos);
    int comp = C.compare(key, curKey);
    if (comp < 0) 
      return treeSearch(key, left(pos));	// search left subtree
    else if (comp > 0)
      return treeSearch(key, right(pos));	// search right subtree
    return pos;		// return internal node where key is found
  }
}


// Adds to L all entries in the subtree rooted at v having keys equal to k
protected void addAll(PositionList<Entry<K,V>> L, Position<Entry<K,V>> v, K k) {
  if (isExternal(v)) return;
  Position<Entry<K,V>> pos = treeSearch(k, v);
  if (!isExternal(pos))  {  // we found an entry with key equal to k 
    addAll(L, left(pos), k);
    L.addLast(pos.element()); 	// add entries in inorder
    addAll(L, right(pos), k);
  } // this recursive algorithm is simple, but it's not the fastest
}

  /** Returns the number of entries in the tree. */
  public int size() { return numEntries; }

  /** Returns whether the tree is empty. */
  public boolean isEmpty() { return size() == 0; }

  /** Returns an entry containing the given key.  Returns null if no such entry exists. */
  public Entry<K,V> find(K key) throws InvalidKeyException {
    checkKey(key);		// may throw an InvalidKeyException
    Position<Entry<K,V>> curPos = treeSearch(key, root());
    actionPos = curPos;		// node where the search ended
    if (isInternal(curPos)) return entry(curPos);
    return null;
  }

  /** Returns an iterable collection of all the entries containing the  given key. */
  public Iterable<Entry<K,V>> findAll(K key) throws InvalidKeyException {
    checkKey(key);		// may throw an InvalidKeyException
    PositionList<Entry<K,V>> L = new NodePositionList<Entry<K,V>>();
    addAll(L, root(), key);
    return L;
  }

  /** Inserts an entry into the tree and returns the newly created entry. */
  public Entry<K,V> insert(K k, V x) throws InvalidKeyException {
    checkKey(k);	// may throw an InvalidKeyException
    Position<Entry<K,V>> insPos = treeSearch(k, root());
    while (!isExternal(insPos))  // iterative search for insertion position
      insPos = treeSearch(k, left(insPos));
    actionPos = insPos;	// node where the new entry is being inserted
    return insertAtExternal(insPos, new BSTEntry<K,V>(k, x, insPos));
  }

  /** Removes and returns a given entry. */
  public Entry<K,V> remove(Entry<K,V> ent) throws InvalidEntryException  {
    checkEntry(ent);            // may throw an InvalidEntryException
    Position<Entry<K,V>> remPos = ((BSTEntry<K,V>) ent).position(); 
    Entry<K,V> toReturn = entry(remPos);	// entry to be returned
    if (isExternal(left(remPos))) remPos = left(remPos);  // left easy case
    else if (isExternal(right(remPos))) remPos = right(remPos); // right easy case
    else {			//  entry is at a node with internal children
      Position<Entry<K,V>> swapPos = remPos;	// find node for moving entry
      remPos = right(swapPos);
      do
	    remPos = left(remPos);
      while (isInternal(remPos));
      replaceEntry(swapPos, (Entry<K,V>) parent(remPos).element());
    }
    actionPos = sibling(remPos);	// sibling of the leaf to be removed
    removeExternal(remPos);
    return toReturn;
  }

  /** Returns an iterator containing all entries in the tree. */
  public Iterable<Entry<K,V>> entries() {
    PositionList<Entry<K,V>> entries = new NodePositionList<Entry<K,V>>();
    Iterable<Position<Entry<K,V>>> positer = positions();
    for (Position<Entry<K,V>> cur: positer)
      if (isInternal(cur))
	entries.addLast(cur.element());
    return entries;
  }


}