private static MergeSortNode MergeRecursively(MergeSortNode left, MergeSortNode right)
{
MergeSortNode head;
MergeSortNode next;
if (left == null)
{
//right.Next = null;
return(right);
}
else if (left.Value < right.Value)
{
head = left;
next = right;
}
else
{
head = right;
next = left;
}
next = Merge(head.Next, next);
head.Next = next;
return(head);
}
public static void Mergesort(int[] items)
{
Queue <MergeSortNode> queue = new Queue <MergeSortNode>();
int length = items.Length;
for (int i = 0; i < length; i++)
{
queue.Enqueue(new MergeSortNode(items[i]));
}
MergeSortNode current = queue.Dequeue();
while (queue.Any())
{
// merge with current
var next = queue.Dequeue();
MergeSortNode head = Merge(current, next);
queue.Enqueue(head);
current = queue.Dequeue();
}
for (int i = 0; i < length; i++)
{
items[i] = current.Value;
current = current.Next;
}
}
public static void MergesortTpl(int[] items)
{
var queue = new Queue <MergeSortNode>();
int length = items.Length;
for (int i = 0; i < length; i++)
{
queue.Enqueue(new MergeSortNode(items[i]));
}
MergeSortNode current = queue.Dequeue();
do
{
var tasks = new Queue <Task <MergeSortNode> >();
while (queue.Any())
{
var next = queue.Dequeue();
var head = current;
tasks.Enqueue(Task.Factory.StartNew(() =>
{
// merge with current
return(Merge(head, next));
}));
current = queue.Any() ? queue.Dequeue() : null;
}
Task.WaitAll(tasks.ToArray());
if (current != null)
{
queue.Enqueue(current);
}
foreach (var task in tasks)
{
queue.Enqueue(task.Result);
}
current = queue.Dequeue();
}while (queue.Any());
for (int i = 0; i < length; i++)
{
items[i] = current.Value;
current = current.Next;
}
}
private static MergeSortNode Merge(MergeSortNode left, MergeSortNode right)
{
MergeSortNode head = null;
MergeSortNode comparisonWinner;
MergeSortNode comparisonLoser = null;
MergeSortNode tail = null;
do
{
if (left.Value < right.Value)
{
comparisonWinner = left;
comparisonLoser = right;
}
else
{
comparisonWinner = right;
comparisonLoser = left;
}
// We need a linked list head on the first iteration
if (head == null)
{
head = comparisonWinner;
}
// We need to link every successive iteration.
if (tail != null)
{
tail.Next = comparisonWinner;
}
left = comparisonWinner.Next;
right = comparisonLoser;
tail = comparisonWinner;
if (left == null)
{
tail.Next = right;
}
} while (left != null);
return(head);
}
