Having hard time to run this one

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Thread: Having hard time to run this one

  1. #1
    Join Date
    May 2005
    Ontario, Canada

    Having hard time to run this one

    package net.datastructures;
    import java.util.Comparator;
    /**  Implementation of an AVL tree. */
     * AVLTree class - implements an AVL Tree by extending a binary
     * search tree.
     * @author Michael Goodrich, Roberto Tamassia, Eric Zamore
    public class AVLTree extends BinarySearchTree implements Dictionary {
      public AVLTree(Comparator c)  { super(c); }
      public AVLTree() { super(); }
      /** Nested class for the nodes of an AVL tree. */ 
      protected static class AVLNode extends BTNode {
        protected int height;  // we add a height field to a BTNode
        AVLNode() {/* default constructor */}
        /** Preferred constructor */
        AVLNode(Object element, BTPosition parent,
    	    BTPosition left, BTPosition right) {
          super(element, parent, left, right);
          height = 0;
          if (left != null) 
            height = Math.max(height, 1 + ((AVLNode) left).getHeight());
          if (right != null) 
            height = Math.max(height, 1 + ((AVLNode) right).getHeight());
        } // we assume that the parent will revise its height if needed
        public void setHeight(int h) { height = h; }
        public int getHeight() { return height; }
      /** Creates a new binary search tree node (overrides super's version). */
      protected BTPosition createNode(Object element, BTPosition parent,
                  BTPosition left, BTPosition right) {
        return new AVLNode(element,parent,left,right);  // now use AVL nodes
      /** Returns the height of a node (call back to an AVLNode). */
      protected int height(Position p)  {
        return ((AVLNode) p).getHeight();
      /** Sets the height of an internal node (call back to an AVLNode). */
      protected void setHeight(Position p)  { // called only if p is internal
        ((AVLNode) p).setHeight(1+Math.max(height(left(p)), height(right(p))));
      /** Returns whether a node has balance factor between -1 and 1. */
      protected boolean isBalanced(Position p)  {
        int bf = height(left(p)) - height(right(p));
        return ((-1 <= bf) &&  (bf <= 1));
      /** Returns a child of p with height no smaller than that of the other child */
        * Return a child of p with height no smaller than that of the
        * other child.
      protected Position tallerChild(Position p)  {
        if (height(left(p)) > height(right(p))) return left(p);
        else if (height(left(p)) < height(right(p))) return right(p);
        // equal height children - break tie using parent's type
        if (isRoot(p)) return left(p);
        if (p == left(parent(p))) return left(p);
        else return right(p);
        * Rebalance method called by insert and remove.  Traverses the path from 
        * zPos to the root. For each node encountered, we recompute its height 
        * and perform a trinode restructuring if it's unbalanced.
      protected void rebalance(Position zPos) {
        while (!isRoot(zPos)) {  // traverse up the tree towards the root
          zPos = parent(zPos);
          if (!isBalanced(zPos)) { 
    	// perform a trinode restructuring at zPos's tallest grandchild
            Position xPos =  tallerChild(tallerChild(zPos));
            zPos = restructure(xPos); // tri-node restructure (from parent class)
            setHeight(left(zPos));  // recompute heights
      // overridden methods of the dictionary ADT
        * Inserts an item into the dictionary and returns the newly created
        * entry. 
      public Entry insert(Object k, Object v) throws InvalidKeyException  {
        Entry toReturn = super.insert(k, v); // calls our new createNode method
        rebalance(actionPos); // rebalance up from the insertion position
        return toReturn;
      /** Removes and returns an entry from the dictionary. */
      public Entry remove(Entry ent) throws InvalidEntryException {
        Entry toReturn = super.remove(ent);
        if (toReturn != null)   // we actually removed something
          rebalance(actionPos);  // rebalance up the tree
        return toReturn;
    } // end of AVLTree class
    I got many error messages.
    Your help is appreciated.

  2. #2
    Join Date
    Dec 2005
    New Jersey
    Can you post the error messages?

  3. #3
    Join Date
    May 2005
    Ontario, Canada

    Package is attached.

    It looks like I have to have a package and I am missing many classes.
    Please see attached files.
    I am using the javac AVLTree\*.java
    I am getting 82 errors, so I could not read the first 40 errors. DOS does not permit me to see them.
    Attached Files Attached Files

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