private void validateTree(LLNode n) {
        boolean left,right;

        if(n.left!=null){
            n.left.prev=n;
            left = true;
        }else{
            left = false;
          //  System.out.println("Left LLNode at Level "+depth+" is empty");

        }
        if(n.right!=null){
            n.right.prev=n;

            right = true;
        }else{
            right = false;
            //System.out.println("Right LLNode at Level "+depth+" is empty");
        }
        if(left){
            validateTree(n.left);

        }
        if(right){
            validateTree(n.right);
  
        }
        
    }