CODEWITHSUNDEEP
javasortingarraylistbinary-search-treeelement
Masteprh33r
Masteprh33r

Reputation: 105

How to convert sorted Arraylist to BST

I have the following code to work with, how could make this method create a BST. I am working Elements.I am using custom imports that can do "T.setRoot()","n.getRightChild()","n.setLeftChild()" and so on, which shouldn't be too hard to figure out. 

public static <E> BTree<E> taulukostaPuu(ArrayList<E> L) {

     BTree<E> T = new BTree<E>();
        //TODO
     return T;
 }

How could i make a recursive method to go through the Arraylist of elements and add them do the BST. I would like to keep this structure intact. All the examples i found were used while the arraylist contained integers, that makes implementing them in element form very difficult. The BST has to be balanced.

I have tried to following: 

private static <E> BTree<E> buildRecursively(ArrayList<E> L,E start,E 
  end,BTree<E> T){
     if (start.compareTo(end) < 0)
         return T;
     E x = L.get((L.size()/2) + (L.size() % 2));
     T.setRoot(new BTreeNode<E>(x)); 
     T.setLeftChild(buildRecursively(L, start, L.get((L.size()/2) + (L.size()  
     %  2)-1)),T);
     T.setRightChild(buildRecursively(L, L.get((L.size()/2) + (L.size() % 
    2)+1), 
    L.get(L.size()-1)),T);

But this obviously this didnt work.

This is what i am currently working with: 

  public static <E> BTree<E> taulukostaPuu(ArrayList<E> L) {

     BTree<E> T = new BTree<E>();

     E root = L.get((L.size()/2) + (L.size() % 2));
     T.setRoot(new BTreeNode<E>(root));


     return T;
}

Not sure where to go from here. I am supposed to somehow traverse the arraylist from x to find the element for the 2 children and do that recursively. Any suggestions?

Upvotes: 0

Views: 678

Answers (1)

John
John

Reputation: 34

Have you checked this click here it's a good start to understand BST, in case you talk about simple BST.

Upvotes: 1

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