Re: Please help for a LinkBinaryTreeInJava

Lew <>
Sun, 16 Mar 2008 15:38:41 -0400
Basanta wrote:

I am new in this group,I don't know how far it would help me.
I tried to make a linked based binary tree following the book "data
structures and algorithms in java" By goodRich and tamassia.I did all
but I wanted to implement a function to determine whether a particular
node exists or not.All I want to implement a function boolean
exists(node n).Can anyone help??My program is as follows:-


interface Node {
        Object getData();
        int getID();

A generic approach (as a matter of style I include the redundant 'public' in
interface declarations):

  interface Node <T>
   T getData();
   Integer getId(); // could parameterize ID type

class LinkBinTree {
      BinNode root;
      int size;
      LinkBinTree(Object O) {
          root = new BinNode(0);

Avoid exorbitant indentation. Up to four spaces per level will suffice.

   class BinNode <T> implements Node <T>


     T data;
     Integer id;

            BinNode left;
            BinNode right;

     public BinNode( Integer iden )

            id = iden;
            left = null;
            right = null;
            data = null;

You don't need to set things to null again.


       BinNode(Object O) {

Why do you have this constructor?

Parameters should have names that start with a lower-case letter: 'o', not 'O'.

            id = 0;
            left = null;
            right = null;
            data = null;

You don't need to set things to null or zero again.


    public T getData() {return data;}

       public int getID() { return id;}

        void addLeft( T obj ) {
             BinNode b = new BinNode(obj);
             left = b;

You don't need 'b':

     left = new BinNode( obj );


        void addRight( T obj ) {
             BinNode r = new BinNode(obj);
             right = r;


      BinNode <T> addLeft(Node <T> n, T o ) // lower-case 'o'!

            throws TreeEmptyException


// braces please:
                  throw new TreeEmptyException("Tree doesn't


//"Tree doesn't exist"


             return n.addLeft( o );


      BinNode <T> addRight( Node <T> n, T o ) throws TreeEmptyException{
    if(!exists(n)) throw new TreeEmptyException("Tree doesn't
            return n.addRight(O);

      void preOrder(Node n) {
              LinkQueueApp<Integer> q =new LinkQueueApp<Integer>();
              int p=n.getID();
              while(!q.isEmpty()) {
                    p =q.dequeue();
                    System.out.println("The pre-order is : "
                    for(int i=p;(i==p+1) || (i==p+2)&&i<=size;i++)


 void boolean exists( Node <T> n ) {
         if(Node == root) return;

You don't show a variable 'root'.

         else {

Are you searching for a certain Node, or a Node with a certain value?

  public static void boolean exists( BinNode <T> root, T value )
   if ( root == null )
   { return false; }
   return (root.value == null? value == null : root.value.equals( value ))
       || exists( root.left, value ) || exists( root.right, value );


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