//== Node.java
public class Node {
    Node left;
    Node right;
    public int value;

    public Node(int v) {
        value = v;
    }
}

//=== BSTIterator.java
class BSTIterator {

    private Node root;

    public BSTIterator(final Node node) {
        root = node;
    }

    public int next() {
        Node pn = root;
        Node cn = root;

        while (cn.left != null) {
            pn = cn;
            cn = cn.left;
        }

        if (pn == cn) {
            root = root.right;
        } else if (cn.right != null) {
            pn.left = cn.right;
        } else {
            pn.left = null;
        }

        return cn.value;
    }

    public boolean hasNext() {
        return root != null;
    }
}

//== BSTIteratorTest.java
import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

public class BSTIteratorTest {

    @Test
    public void testBSTIterator() throws Exception {
        Node root = new Node(19);
        root.left = new Node(5);
        root.left.left = new Node(2);
        root.left.left.left = new Node(1);
        root.left.left.right = new Node(4);
        root.left.right = new Node(9);
        root.left.right.left = new Node(7);
        root.left.right.right = new Node(14);
        root.right = new Node(33);
        root.right.left = new Node(21);
        root.right.left.left = new Node(20);
        root.right.left.right = new Node(25);
        root.right.left.right.right = new Node(27);
        root.right.right = new Node(38);
        root.right.right.left = new Node(37);
        root.right.right.right = new Node(39);

        BSTIterator i = new BSTIterator(root);
        StringBuilder sb = new StringBuilder();
        int prev = -1;
        while(i.hasNext()) {
            int curr = i.next();
            assertTrue(curr > prev);
            sb.append(curr);
            sb.append(' ');
        }
        assertEquals("1 2 4 5 7 9 14 19 20 21 25 27 33 37 38 39 ", sb.toString());
    }
}