Balanced Binary Search Tree

Question

I need to build a balanced binary search tree. So far my program inserts the numbers from 1 to 26, but my program does not build it into a balanced binary search tree. If an

Answer 1

public class BinarySearchTree {
  TreeNode root;

  public BinarySearchTree(){
    root = new TreeNode();
  }

  public TreeNode getRoot(){
    return root;
  }
  public void insert(int data) {
    root = insert(root, data);
  }//Insert method checking to see where to put the nodes

//  public void insert(TreeNode node, int data){
//    TreeNode node1 = new TreeNode(data);
//    if (root == null) { 
//      root = node1; 
//    } 
//    else{
//      TreeNode parIns = root;//Parent
//      TreeNode insNode = root;//Insertion Node
//      
//      while(insNode != null){
//        parIns = insNode;
//        
//        if(data < insNode.getData()){//If the data is less than the data coming in place it on the left
//          insNode = insNode.getLeft();
//        }else{//Place it on the right
//          insNode = insNode.getRight();
//        }
//      }//Searching where to put the node
//      
//      if(data < parIns.getData()){
//        parIns.setLeft(node1);
//      }else{
//        parIns.setRight(node1);
//      }
//      
//    }
//  }

  private TreeNode insert(TreeNode node, int data) { 
    if(root.data == 0)
      root.data = data;
    else if (node==null) { 
      node = new TreeNode(data); 
    } 
    else { 
      if (data <= node.data) { 
        node.leftTreeNode = insert(node.leftTreeNode, data); 
      } 
      else { 
        node.rightTreeNode = insert(node.rightTreeNode, data); 
      } 
    } 

    return(node); // in any case, return the new pointer to the caller 
  } 
  public void printPreOrder(){
    printPreOrder(root);
  }
  public void printPreOrder(TreeNode n){
    if(n != null){
      n.print();//N
      printPreOrder(n.getLeft());//L
      printPreOrder(n.getRight());//R
    }
  }

    public TreeNode balance(int[] a, int start, int end){
    TreeNode node = new TreeNode();
    if(start <= end){
      int mid = start + (end - start) /2;
      node.data = a[mid];

      if(root.data == 0)
        root = node;
      node.leftTreeNode = balance(a, start, mid -1);/*Make the left child if the node coming in is
       less than the mid node */


      node.rightTreeNode = balance(a, mid + 1, end);/*Make the rigth child if the node is
       greater than the mid node*/
    }
      else{
      return null;
      }


    return node;
  }



  public static void main(String[] args) {
    BinarySearchTree tree = new BinarySearchTree();
    //int[] a = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,21,22,23,24,25,26};
    int[] a = new int[26];
    for(int i = 0; i < 26; i++){
      a[i] = i + 1;
    }
    for(int i = 1; i <= 26; i++)
      tree.insert(i);

    tree.printPreOrder();
    BinarySearchTree tree2 = new BinarySearchTree();
    tree2.balance(a, 0, 25);
    System.out.println("Now I am going to balance my tree");
    tree2.printPreOrder();

  }

}



public class TreeNode {

  TreeNode leftTreeNode, rightTreeNode;// the nodes
  int data;
  //int size;



  public TreeNode(){//Constructer
    leftTreeNode = null;
    rightTreeNode = null;
    data = 0;
  }

  public TreeNode(int newData){//Constructer with new Data coming in for comparison
    leftTreeNode = null;
    rightTreeNode = null;
    data = newData;
  }

  public TreeNode getLeft(){
    return leftTreeNode;
  }
  public TreeNode getRight(){
    return rightTreeNode;
  }

  public void setLeft(TreeNode leftTreeNode){
    this.leftTreeNode = leftTreeNode;
  }
  public void setRight(TreeNode rightTreeNode){
    this.rightTreeNode = rightTreeNode;
  }
  public int getData(){
    return data;
  }


//    public boolean isEmpty(){//Checking to see if the the root is empty
//      if(size == 0) return true;
//      else return false;



  public void print(){
    System.out.println("Data is: " + getData());
  }


}