public static int QuickSort <T>(this T[] arr, PivotChoice choice = PivotChoice.ChooseRandom)
where T : IComparable <T>
{
ChoosePivotIndex <T> pivotIntFunc = CalcMedium;
switch (choice)
{
case PivotChoice.AlwaysFirst:
pivotIntFunc = (T[] ar, int left, int right) => left;
break;
case PivotChoice.AlwaysLast:
pivotIntFunc = (T[] ar, int left, int right) => right;
break;
case PivotChoice.CalcMedium:
pivotIntFunc = CalcMedium;
break;
case PivotChoice.ChooseRandom:
Random rnd = new Random();
pivotIntFunc = (T[] ar, int left, int right) => rnd.Next(left, right + 1);
break;
}
return(Sort <T>(arr, 0, arr.Length - 1, pivotIntFunc));
}
private static int Sort <T>(T[] arr, int left, int right, ChoosePivotIndex <T> pivotIntFunc)
where T : IComparable <T>
{
int result = left < right ? right - left : 0;
if (left < right + 1)
{
int pivotInd = pivotIntFunc(arr, left, right);
pivotInd = Pivot(arr, left, right, pivotInd);
if (left < pivotInd - 1)
{
result += Sort <T>(arr, left, pivotInd - 1, pivotIntFunc);
}
if (pivotInd + 1 < right)
{
result += Sort <T>(arr, pivotInd + 1, right, pivotIntFunc);
}
}
return(result);
}
