Function successorHelper

structure/tree/tree.go:173–189

(node, nilNode Node[T])

}

func successorHelper[T constraints.Ordered](node, nilNode Node[T]) (T, bool) {
	if node.Right() != nilNode {
		return minimum(node.Right(), nilNode).Key(), true
	}

	p := node.Parent()
	for p != nilNode && node == p.Right() {
		node = p
		p = p.Parent()
	}

	if p == nilNode {
		var dft T
		return dft, false
	}
	return p.Key(), true
}