Subversion Repositories programming

// Written by Ira Snyder

// Due Date: 11-24-2004

// Project #4

import java.io.*;

import java.util.*;

class AVLTree {

    private int key, height;

    private AVLTree left, right;

    public static final AVLTree NIL = new AVLTree();

    public AVLTree( int key ) {

        this.key = key;

        left = right = NIL;

    }

    public boolean add( int key ) {

        int oldSize = size();

        grow(key);

        return size() > oldSize;

    }

    public AVLTree grow( int key ) {

        if( this == NIL ) return new AVLTree(key);

        if( key == this.key ) return this; //prevent key dupes

        if( key < this.key ) left = left.grow(key);

        else right = right.grow(key);

        rebalance();

        height = 1 + Math.max(left.height,right.height);

        return this;

    }

    public int size() {

        if( this == NIL ) return 0;

        return 1 + left.size() + right.size();

    }

    //I like the BinaryTree toString better than the author's toString()

    //so I used it here instead. I left the author's code for completeness.

    /*

    public String toString() {

        if( this == NIL ) return "";

        return left + " " + key + " " + right;

    }

    */

    public String toString() {

        if( this == NIL ) return "()";

        String sLeft = sLeft = left.toString();

        String sRight = sRight = right.toString();

        String answer = new String();

        //assemble the string to return

        answer = "(";

        if( !sLeft.equals("()") ) { answer += sLeft + ","; }

        answer += key;

        if( !sRight.equals("()") ) { answer += "," + sRight; }

        answer += ")";

        //return the assembled string

        return answer;

    }

    private AVLTree() { //construct the empty tree

        left = right = this;

        height = -1;

    }

    private AVLTree( int key, AVLTree left, AVLTree right ) {

        this.key = key;

        this.left = left;

        this.right = right;

        height = 1 + Math.max(left.height,right.height);

    }

    private void rebalance() {

        if( right.height > (left.height + 1) ) {

            if( right.left.height > right.right.height ) right.rotateRight();

            rotateLeft();

        }

        else if( left.height > (right.height + 1) ) {

            if( left.right.height > left.left.height ) left.rotateLeft();

            rotateRight();

        }

    }

    private void rotateLeft() {

        left = new AVLTree(key,left,right.left);

        key = right.key;

        right = right.right;

    }

    private void rotateRight() {

        right = new AVLTree(key,left.right,right);

        key = left.key;

        left = left.left;

    }

    // new functions from Prog. Probs PG 411

    public int getHeight() { return height; }

    public AVLTree getLeft() { 

        if( this == NIL ) { return NIL; }

        return left;

    }

    public AVLTree getRight() { 

        if( this == NIL ) { return NIL; }

        return right;

    }

    public int getRoot() {

        return key;

    }

    public boolean contains( int x ) { 

        if( this == NIL ) { return false; }

        if( key == x ) { return true; }

        return left.contains(x) || right.contains(x);

    }

    // am guessing this returns the tree with x == key as the root

    public AVLTree get( int x ) {

        if( this == NIL ) { return NIL; }

        if( x == key ) { return this; }

        if( x < key ) { return left.get(x); }

        return right.get(x);

    }

    public boolean equals( Object object ) { 

        if( !(object instanceof AVLTree) ) { return false; }

        AVLTree temp = (AVLTree)object; //make it typed

        boolean l=false, r=false;

        //check the left

        if( left == NIL && temp.left == NIL ) l = true;

        else l = left.equals(temp.left);

        //check the right

        if( right == NIL && temp.right == NIL ) r = true;

        else r = right.equals(temp.right);

        return (temp.key == key) && l && r;

    }

    public AVLTree( int[] a ) { 

        this(a[0]); //create a new tree

        //call add() for every element in the array

        for( int i=1; i < a.length; i++ ) add(a[i]);

    }

    /*

    public boolean remove( int key ) { 

        if( this == NIL ) { return false; }

        if( key < this.key ) { return left.remove(key); }

        if( key > this.key ) { return right.remove(key); }

        if( left == NIL && right == NIL ) { this = NIL; return true; }

        if( left == NIL ) { 

            this = new AVLTree(right.key,right.left,right.right);

            return true;

        }

        if( right == NIL ) {

            this = new AVLTree(left.key,left.left,left.right);

            return true;

        }

        this = new AVLTree( deleteMinimum(right) );

        rebalance(); //fix the balance

        return true;

    }

    private int deleteMinimum( AVLTree tree ) {

        int tempKey=0;

        if( left == NIL ) { 

            tempKey = key;

            this = new AVLTree(right.key,right.left,right.right);

        }

        if( left.left == NIL && left.right == NIL ) {

            tempKey = key;

            this = new AVLTree(left.key,left.left,right.right);

        }

        return deleteMinimum(left);

    }

    */

} //end AVLTree class