private void compute() {
Stack<BSTNode> stack = new Stack<>();
BSTNode<Integer, String> lastVisitedNode = null;
while (node != null || !stack.isEmpty()) {
if (node != null) {
stack.add(node);
node = node.left();
} else {
BSTNode<Integer, String> peekNode = stack.peek();
if (peekNode.right() != null && lastVisitedNode.element() != peekNode.right().element()) {
node = peekNode.right();
} else {
if (peekNode.right() == null) System.out.println(stack);
lastVisitedNode = stack.pop();
}
}
}
}
