public static int FindOrderStatisticsRecursive(int[] array, int i)
{
if (i < 1 || i > array.Length)
{
throw new ArgumentOutOfRangeException($"There is no {i}th smallest index in the array");
}
if (array.Length == 1)
{
return(array[0]);
}
var pivotPartitioner = new PivotPartitioner(PivotSelect.Random);
i--;
var pivot = pivotPartitioner.Partition(array, 0, array.Length - 1);
if (pivot == i)
{
return(array[i]);
}
if (pivot < i)
{
var rightArray = array.Skip(pivot + 1).ToArray();
return(FindOrderStatisticsRecursive(rightArray, i - pivot));
}
var leftArray = array.Take(pivot + 1).ToArray();
return(FindOrderStatisticsRecursive(leftArray, i + 1));
}
public static int FindOrderStatistics(int[] array, int i)
{
if (i < 1 || i > array.Length)
{
throw new ArgumentOutOfRangeException($"There is no {i}th smallest index in the array");
}
var pivotPartitioner = new PivotPartitioner(PivotSelect.Random);
i--;
var startIndex = 0;
var endIndex = array.Length - 1;
var pivot = pivotPartitioner.Partition(array, startIndex, endIndex);
while (pivot != i)
{
if (pivot > i)
{
endIndex = pivot - 1;
pivot = pivotPartitioner.Partition(array, startIndex, endIndex);
}
else
{
startIndex = pivot + 1;
pivot = pivotPartitioner.Partition(array, startIndex, endIndex);
}
}
return(array[pivot]);
}
public QuicksortComparesCounter(int[] array, PivotSelect pivotSelectionMethod)
{
Partitioner = new PivotPartitioner(pivotSelectionMethod);
QuickSort(array);
}