static void Main(string[] args)
{
var data = new SwappableData(5, 2, 7, 4, 1, 6, 3);
PartitionStrategy partition = PartitionUtil.DoublePointerPartition;
Quicksort(data, 0, data.Length - 1, partition);
Console.WriteLine(data);
}
static void Quicksort(SwappableData data, int begin, int end, PartitionStrategy partition)
{
if (begin < end)
{
var mid = partition(data, begin, end);
Quicksort(data, begin, mid, partition);
Quicksort(data, mid + 1, end, partition);
}
}
internal static int BasicPartition(SwappableData data, int begin, int end)
{
var pivot = data[begin];
var rightBegin = begin + 1;
for (var i = rightBegin; i <= end; i++)
{
if (data[i] < pivot)
{
data.Swap(i, rightBegin);
rightBegin++;
}
}
var mid = rightBegin - 1;
data.Swap(begin, mid);
return(mid);
}
internal static int DoublePointerPartition(SwappableData data, int begin, int end)
{
var mid = (int)((begin + end) / 2);
var pivot = MedianOfThree(data[begin], data[mid], data[end]);
var i = begin - 1;
var j = end + 1;
while (true)
{
while (true)
{
i++;
if (data[i] >= pivot)
{
break;
}
}
while (true)
{
j--;
if (data[j] <= pivot)
{
break;
}
}
if (i < j)
{
if (data[i] != data[j])
{
data.Swap(i, j);
}
}
else
{
return(j);
}
}
}