
import java.util.Iterator;

public class Exercise25_10 {
  public static void main(String[] args) {
    new Exercise25_10();
  }
  
  public Exercise25_10() {
    BST<String> tree = new BST<>();
    tree.insert("London");
    tree.insert("Paris");
    tree.insert("Berlin");
    tree.insert("Washington");
    tree.insert("Rome");
    
    Iterator<String> iterator = tree.preorderIterator();
    while (iterator.hasNext()) {
      System.out.println(iterator.next());
    }
  }

  public static class BST<E extends Comparable<E>> 
      extends AbstractTree<E> {
    protected TreeNode<E> root;
    protected int size = 0;

    /** Create a default binary tree */
    public BST() {
    }

    /** Create a binary tree from an array of objects */
    public BST(E[] objects) {
      for (int i = 0; i < objects.length; i++)
        insert(objects[i]);
    }

    @Override /** Returns true if the element is in the tree */
    public boolean search(E e) {
      TreeNode<E> current = root; // Start from the root

      while (current != null) {
        if (e.compareTo(current.element) < 0) {
          current = current.left;
        }
        else if (e.compareTo(current.element) > 0) {
          current = current.right;
        }
        else // element matches current.element
          return true; // Element is found
      }

      return false;
    }

    @Override /** Insert element o into the binary tree
     * Return true if the element is inserted successfully */
    public boolean insert(E e) {
      if (root == null)
        root = createNewNode(e); // Create a new root
      else {
        // Locate the parent node
        TreeNode<E> parent = null;
        TreeNode<E> current = root;
        while (current != null)
          if (e.compareTo(current.element) < 0) {
            parent = current;
            current = current.left;
          }
          else if (e.compareTo(current.element) > 0) {
            parent = current;
            current = current.right;
          }
          else
            return false; // Duplicate node not inserted

        // Create the new node and attach it to the parent node
        if (e.compareTo(parent.element) < 0)
          parent.left = createNewNode(e);
        else
          parent.right = createNewNode(e);
      }

      size++;
      return true; // Element inserted successfully
    }

    protected TreeNode<E> createNewNode(E e) {
      return new TreeNode<E>(e);
    }

    @Override /** Inorder traversal from the root*/
    public void inorder() {
      inorder(root);
    }

    /** Inorder traversal from a subtree */
    protected void inorder(TreeNode<E> root) {
      if (root == null) return;
      inorder(root.left);
      System.out.print(root.element + " ");
      inorder(root.right);
    }

    @Override /** Postorder traversal from the root */
    public void postorder() {
      postorder(root);
    }

    /** Postorder traversal from a subtree */
    protected void postorder(TreeNode<E> root) {
      if (root == null) return;
      postorder(root.left);
      postorder(root.right);
      System.out.print(root.element + " ");
    }

    @Override /** Preorder traversal from the root */
    public void preorder() {
      preorder(root);
    }

    /** Preorder traversal from a subtree */
    protected void preorder(TreeNode<E> root) {
      if (root == null) return;
      System.out.print(root.element + " ");
      preorder(root.left);
      preorder(root.right);
    }

    /** This inner class is static, because it does not access 
        any instance members defined in its outer class */
    public static class TreeNode<E extends Comparable<E>> {
      protected E element;
      protected TreeNode<E> left;
      protected TreeNode<E> right;

      public TreeNode(E e) {
        element = e;
      }
    }

    @Override /** Get the number of nodes in the tree */
    public int getSize() {
      return size;
    }

    /** Returns the root of the tree */
    public TreeNode<E> getRoot() {
      return root;
    }

    /** Returns a path from the root leading to the specified element */
    public java.util.ArrayList<TreeNode<E>> path(E e) {
      java.util.ArrayList<TreeNode<E>> list =
        new java.util.ArrayList<TreeNode<E>>();
      TreeNode<E> current = root; // Start from the root

      while (current != null) {
        list.add(current); // Add the node to the list
        if (e.compareTo(current.element) < 0) {
          current = current.left;
        }
        else if (e.compareTo(current.element) > 0) {
          current = current.right;
        }
        else
          break;
      }

      return list; // Return an array list of nodes
    }

    @Override /** Delete an element from the binary tree.
     * Return true if the element is deleted successfully
     * Return false if the element is not in the tree */
    public boolean delete(E e) {
      // Locate the node to be deleted and also locate its parent node
      TreeNode<E> parent = null;
      TreeNode<E> current = root;
      while (current != null) {
        if (e.compareTo(current.element) < 0) {
          parent = current;
          current = current.left;
        }
        else if (e.compareTo(current.element) > 0) {
          parent = current;
          current = current.right;
        }
        else
          break; // Element is in the tree pointed at by current
      }

      if (current == null)
        return false; // Element is not in the tree

      // Case 1: current has no left child
      if (current.left == null) {
        // Connect the parent with the right child of the current node
        if (parent == null) {
          root = current.right;
        }
        else {
          if (e.compareTo(parent.element) < 0)
            parent.left = current.right;
          else
            parent.right = current.right;
        }
      }
      else {
        // Case 2: The current node has a left child
        // Locate the rightmost node in the left subtree of
        // the current node and also its parent
        TreeNode<E> parentOfRightMost = current;
        TreeNode<E> rightMost = current.left;

        while (rightMost.right != null) {
          parentOfRightMost = rightMost;
          rightMost = rightMost.right; // Keep going to the right
        }

        // Replace the element in current by the element in rightMost
        current.element = rightMost.element;

        // Eliminate rightmost node
        if (parentOfRightMost.right == rightMost)
          parentOfRightMost.right = rightMost.left;
        else
          // Special case: parentOfRightMost == current
          parentOfRightMost.left = rightMost.left;     
      }

      size--;
      return true; // Element deleted successfully
    }

    /** Returns an iterator for traversing the elements in preorder */
    java.util.Iterator<E> preorderIterator() {
      return new PreorderIterator();
    }

    
    @Override /** Obtain an iterator. Use inorder. */
    public java.util.Iterator<E> iterator() {
      return new InorderIterator();
    }

    // Inner class InorderIterator
    private class InorderIterator implements java.util.Iterator<E> {
      // Store the elements in a list
      private java.util.ArrayList<E> list =
        new java.util.ArrayList<E>();
      private int current = 0; // Point to the current element in list

      public InorderIterator() {
        inorder(); // Traverse binary tree and store elements in list
      }

      /** Inorder traversal from the root*/
      private void inorder() {
        inorder(root);
      }

      /** Inorder traversal from a subtree */
      private void inorder(TreeNode<E> root) {
        if (root == null)return;
        inorder(root.left);
        list.add(root.element);
        inorder(root.right);
      }

      @Override /** More elements for traversing? */
      public boolean hasNext() {
        if (current < list.size())
          return true;

        return false;
      }

      @Override /** Get the current element and move to the next */
      public E next() {
        return list.get(current++);
      }

      @Override /** Remove the current element */
      public void remove() {
        delete(list.get(current)); // Delete the current element
        list.clear(); // Clear the list
        inorder(); // Rebuild the list
      }
    }

    /** Remove all elements from the tree */
    public void clear() {
      root = null;
      size = 0;
    }
  
    // Inner class PreorderIterator
    private class PreorderIterator implements java.util.Iterator<E> {
      // Store the elements in a list
      private java.util.ArrayList<E> list =
        new java.util.ArrayList<>();
      private int current = 0; // Point to the current element in list

      public PreorderIterator() {
        preorder(); // Traverse binary tree and store elements in list
      }

      private void preorder() {
        preorder(root);
      }

      private void preorder(TreeNode<E> root) {
        if (root == null)return;
        list.add(root.element);
        preorder(root.left);
        preorder(root.right);
      }

      @Override /** More elements for traversing? */
      public boolean hasNext() {
        if (current < list.size())
          return true;

        return false;
      }

      @Override /** Get the current element and move to the next */
      public E next() {
        return list.get(current++);
      }

      @Override /** Remove the current element */
      public void remove() {
        delete(list.get(current)); // Delete the current element
        list.clear(); // Clear the list
        inorder(); // Rebuild the list
      }
    }
  }
}