private static void StartLeftTask <T>(T[] array, QuickSortMode quickSortMode, int end, int anchor)
where T : IComparable <T>
{
var task = new Task(() => QuickSortInner(array, quickSortMode, anchor + 1, end),
TaskCreationOptions.AttachedToParent);
task.Start();
}
public static void Start <T>(T[] array, QuickSortMode quickSortMode = QuickSortMode.Serial)
where T : IComparable <T>
{
if (quickSortMode == QuickSortMode.Serial)
{
QuickSortInner(array, quickSortMode);
return;
}
// Task.Run is not appropriate, because it is using TaskCreationOptions.DenyChildAttach
var task = new Task(() => QuickSortInner(array, quickSortMode));
task.Start();
task.Wait();
}
private static void QuickSortInner <T>(T[] array, QuickSortMode quickSortMode = QuickSortMode.Serial,
int start = 0, int end = -1) where T : IComparable <T>
{
if (end == -1)
{
end = array.Length - 1;
}
if (end - start == 1 && array[start].CompareTo(array[end]) > 0)
{
// case of two items
var c = array[end];
array[end] = array[start];
array[start] = c;
return;
}
// case of three or more items
var anchor = (start + end) / 2;
var startPointForSecondPart = anchor + 1;
for (var i = 0; i < anchor; i++)
{
// if (array[i] <= array[anchor])
if (array[i].CompareTo(array[anchor]) <= 0)
{
continue;
}
// need to swap
var swapI = i;
if (anchor - i > 1)
{
var preAnchor = anchor - 1;
var z = array[i];
array[i] = array[preAnchor];
array[preAnchor] = z;
swapI = preAnchor;
i = i - 1;
}
var z2 = array[swapI];
array[swapI] = array[anchor];
array[anchor] = z2;
anchor = anchor - 1;
}
for (var i = startPointForSecondPart; i <= end; i++)
{
if (array[i].CompareTo(array[anchor]) >= 0)
{
continue;
}
// need to swap
var swapI = i;
if (i - anchor > 1)
{
var postAnchor = anchor + 1;
var z = array[i];
array[i] = array[postAnchor];
array[postAnchor] = z;
swapI = postAnchor;
}
var z2 = array[swapI];
array[swapI] = array[anchor];
array[anchor] = z2;
anchor = anchor + 1;
}
if (start < anchor - 1)
{
if (quickSortMode == QuickSortMode.Serial)
{
QuickSortInner(array, quickSortMode, start, anchor - 1);
}
else
{
StartRightTask(array, quickSortMode, start, anchor);
}
}
if (anchor + 1 < end)
{
if (quickSortMode == QuickSortMode.Serial)
{
QuickSortInner(array, quickSortMode, anchor + 1, end);
}
else
{
StartLeftTask(array, quickSortMode, end, anchor);
}
}
}