recursive method to balance a binary tree

[tomas fleen]

hi, my problem:

write a method that recursive balance a binary tree from data held in an array

1. Store element i an array. fixed!
2. Emptry the tree fixed!
3. rebuild the tree recursive

I dont now how to do number 3!?!?!?

I appreciate all the help i can get!

code:

public class Node

public class Node
{
private int data;
private Node left;
private Node right;

public Node(int initialData, Node initialLeft, Node initialRight)
{
data=initialData;
left=initialLeft;
right=initialRight;
}
public int getData()
{
return data;
}

public Node getLeft()
{
return left;
}

public Node getRight()
{
return right;
}
public void setLeft(Node newLeft)
{
left=newLeft;
}

public void setRight(Node newRight)
{
right=newRight;
}
}

/code

public class IntTreeBag

code :

public class IntTreeBag
{
private Node root;

public IntTreeBag()
{
root=null;
}

public void add(Node cursor, int element)
{
if(root==null)
{
root = new Node(element,null,null);
return;
}
if(element==cursor.getData())
{
JOptionPane.showMessageDialog(null, "Datat finns redan i ditt tr�d!");
return;
}
if(element<cursor.getData())
{
if(cursor.getLeft()==null)
{
Node newnode = new Node(element,null,null);
cursor.setLeft(newnode);
}
else
add(cursor.getLeft(),element);
}
if(element>cursor.getData())
{
if(cursor.getRight()==null)
{
Node newnode = new Node(element,null,null);
cursor.setRight(newnode);
}
else
add(cursor.getRight(),element);
}
}
private int howmanyNodes(Node cursor)
{
if (cursor==null)
{
return(0);
}
else
{
return(howmanyNodes(cursor.getLeft()) + 1 +howmanyNodes(cursor.getRight()));
}
}
public int[] toSortedArray()
{
int non = howmanyNodes();
int[] array = new int[non];
Order(getRoot(), array, 0);
return array;
}

private int Order(Node cursor, int[] array, int i)
{
if(cursor != null)
{
i = Order(cursor.getLeft(), array, i);
array[i++] = cursor.getData();
i = Order(cursor.getRight(), array, i);
}
return i;
}
}
/code

[Steve Fahlbusch]

what is the approach and are there any other constraints?

Are you going to add basically one node to the tree at a time and balance each time?

Are you going to add all of the nodes, then balance?

Are you going to load a series of small trees, then thread back to a balanced tree?

Are you going to order the nodes from the array so that the binary tree will be balanced on creation?

Are there any rules as to the delta of branches before a balance is done?

[tomas fleen]

all nodes(elements) from the array should be added whit an recursive method that balance at the same time, if it is possible?!?!

middle value from array as root
left part of the array to the left part of the tree
right part of the array to the right part of the tree

[Steve Fahlbusch]

Well you really have your method

Node addTree( array )
node = new Node
node.data = array( middle_value )
node.left = addTree ( array( from zero up to 1 less than middle_value ))
node.right = addTree ( array( from middle_value + 1 up to length))
return node