private AANode<T> getSuccessor(AANode<T> node) {
AANode<T> successor = node.getRight();
while (successor.getLeft() != null) {
successor = successor.getLeft();
}
return successor;
}
private AANode<T> getPredecessor(AANode<T> node) {
AANode<T> predecessor = node.getLeft();
while (predecessor.getRight() != null) {
predecessor = predecessor.getRight();
}
return predecessor;
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
AANode<T> current = stack.pop();
pushLeftChildren(current.getRight());
return current.getValue();
}
private AANode<T> split(AANode<T> node) {
if (node == null) {
return null;
} else if (node.getLeft() == null) {
return node;
} else if (node.getLeft().getLevel() == node.getLevel()) {
AANode<T> left = node.getLeft();
node.setLeft(left.getRight());
left.setRight(node);
return left;
} else {
return node;
}
}
private AANode<T> insert(T element, AANode<T> node) {
if (node == null) {
node = new AANode<>(element);
} else if (element.compareTo(node.getValue()) < 0) {
node.setLeft(insert(element, node.getLeft()));
} else if (element.compareTo(node.getValue()) > 0) {
node.setRight(insert(element, node.getRight()));
} else {
return node;
}
node = skew(node);
node = split(node);
return node;
}
private AANode<T> decreaseLevel(AANode<T> node) {
int shouldBe = 0;
if (node.getLeft() != null && node.getRight() != null) {
shouldBe = Math.min(node.getLeft().getLevel(), node.getRight().getLevel()) + 1;
} else if (node.getLeft() != null) {
shouldBe = node.getLeft().getLevel() + 1;
} else if (node.getRight() != null) {
shouldBe = node.getRight().getLevel() + 1;
} else {
return node;
}
if (shouldBe < node.getLevel()) {
node.setLevel(shouldBe);
if (shouldBe < node.getRight().getLevel()) {
node.getRight().setLevel(shouldBe);
}
}
return node;
}
private AANode<T> remove(T element, AANode<T> node) {
if (node == null) {
return node;
} else if (element.compareTo(node.getValue()) > 0) {
node.setRight(remove(element, node.getRight()));
} else if (element.compareTo(node.getValue()) < 0) {
node.setLeft(remove(element, node.getLeft()));
} else {
if (node.getLevel() == 1) {
return null;
} else if (node.getLeft() == null) {
AANode<T> left = getSuccessor(node);
node.setRight(remove(left.getValue(), node.getRight()));
node.setValue(left.getValue());
} else {
AANode<T> left = getPredecessor(node);
node.setLeft(remove(left.getValue(), node.getLeft()));
node.setValue(left.getValue());
}
}
node = decreaseLevel(node);
node = skew(node);
node.setRight(skew(node.getRight()));
if (node.getRight() != null) {
node.getRight().setRight(skew(node.getRight().getRight()));
}
node = split(node);
node.setRight(split(node).getRight());
return node;
}
private void pushLeftChildren(AANode<T> current) {
while (current != null) {
stack.push(current);
current = current.getLeft();
}
}
private AANode<T> skew(AANode<T> node) {
if (node == null) {
return null;
} else if (node.getRight() == null || node.getRight().getRight() == null) {
return node;
} else if (node.getLevel() == node.getRight().getRight().getLevel()) {
AANode<T> right = node.getRight();
node.setRight(right.getLeft());
right.setLeft(node);
right.setLevel(right.getLevel() + 1);
return right;
} else {
return node;
}
}
