/**
* Remove an element from the left digit.
*
* @param pos position inside the left digit
* @return resulting tree
*/
private FingerTree<N, E> removeLeft(final long pos) {
if (left.length > 1) {
// left digit cannot underflow, just delete the element
return new DeepTree<>(remove(left, pos), leftSize - 1, middle, right, size - 1);
}
// singleton digit might underflow
final Node<N, E> node = left[0];
if (!middle.isEmpty()) {
// next node for balancing is in middle tree
final InnerNode<N, E> head = (InnerNode<N, E>) middle.head();
final Node<N, E> first = head.getSub(0);
final NodeLike<N, E>[] rem = node.remove(null, first, pos);
final Node<N, E> newNode = (Node<N, E>) rem[1], newFirst = (Node<N, E>) rem[2];
if (newNode == null) {
// nodes were merged
final Node<N, E>[] newLeft = head.children.clone();
newLeft[0] = newFirst;
return get(newLeft, middle.tail(), right, size - 1);
}
@SuppressWarnings("unchecked")
final Node<N, E>[] newLeft = new Node[] {newNode};
if (newFirst != first) {
// nodes were balanced
final FingerTree<Node<N, E>, E> newMid = middle.replaceHead(head.replaceFirst(newFirst));
return new DeepTree<>(newLeft, newNode.size(), newMid, right, size - 1);
}
// no changes to this tree's structure
return new DeepTree<>(newLeft, newNode.size(), middle, right, size - 1);
}
// potentially balance with right digit
final NodeLike<N, E>[] rem = node.remove(null, right[0], pos);
final Node<N, E> newNode = (Node<N, E>) rem[1], newFirstRight = (Node<N, E>) rem[2];
if (newNode == null) {
// nodes were merged
if (right.length == 1) return new SingletonTree<>(newFirstRight);
final int mid = right.length / 2;
final Node<N, E>[] newLeft = slice(right, 0, mid);
newLeft[0] = newFirstRight;
return get(newLeft, middle, slice(right, mid, right.length), size - 1);
}
// structure does not change
@SuppressWarnings("unchecked")
final Node<N, E>[] newLeft = new Node[] {newNode};
if (newFirstRight == right[0]) {
// right digit stays the same
return new DeepTree<>(newLeft, newLeft[0].size(), middle, right, size - 1);
}
// adapt the right digit
final Node<N, E>[] newRight = right.clone();
newRight[0] = newFirstRight;
return new DeepTree<>(newLeft, newNode.size(), middle, newRight, size - 1);
}
