// Hoare Partition Scheme
// https://en.wikipedia.org/wiki/Quicksort#Hoare_partition_scheme
protected override async Task <int> Split(IList list, int low, int high)
{
// Select a pivot
var pivot = list[(high + low) / 2];
// Get initial index of smaller side
var ii = low;
var jj = high;
// Begin swapping elements to ensure those less than the pivot are to the left
// and those greater than or equal to the pivot are on the right
while (true)
{
await Task.Delay(1);
while (AbstractOrder.LessThan(list[ii], pivot))
{
ii++;
}
while (AbstractOrder.GreaterThan(list[jj], pivot))
{
jj--;
}
if (ii >= jj)
{
return(jj + 1); // +1 to account for base Sorter using -1 instead of +1 for the recursive calls
}
Swap(list, ii, jj);
ii++;
jj--;
}
}
protected override async Task Join(IList list, int low, int splitIndex, int high)
{
int jj;
var key = list[high]; // Pick the last element in the array to insert
// Begin shuffling any elements larger than the key over to the right
for (jj = high; low < jj && AbstractOrder.LessThan(key, list[jj - 1]); jj--)
{
await Task.Delay(1);
list[jj] = list[jj - 1];
}
list[jj] = key; // Insert the key at it's final position
}