private static SinglyNode <int> InternalMergeSort(this SinglyNode <int> node)
{
if (node == null)
{
Throw.ArgumentNullException(nameof(node));
}
if (node.Next == null)
{
return(node);
}
var middle = node.InternalMiddleNode();
var secondHalf = middle.Next;
middle.Next = null;
var left = InternalMergeSort(node);
var right = InternalMergeSort(secondHalf);
return(InternalMerge(left, right));
}
