package utility.euler_tour;

import tree.binarytree.*;
import position.Position;



public abstract class EulerTour<E, R> {
  protected BinaryTree<E> tree;

  public abstract R execute(BinaryTree<E> T);

  protected void init(BinaryTree<E> T) { tree = T; }

  protected R eulerTour(Position<E> v) {
    TourResult<R> r = new TourResult<R>();
    visitLeft(v, r);
    if (tree.hasLeft(v))
      r.left = eulerTour(tree.left(v));
    visitBelow(v, r);
    if (tree.hasRight(v))
      r.right = eulerTour(tree.right(v));
    visitRight(v, r);
    return r.out;
  }

  protected void visitLeft(Position<E> v, TourResult<R> r) {}

  protected void visitBelow(Position<E> v, TourResult<R> r) {}

  protected void visitRight(Position<E> v, TourResult<R> r) {}


  public class TourResult<R> {
    public R left;
    public R right;
    public R out; 
  }

}