public static List <int> Sort(int[] input)
{
if (input == null || input.Length < 2)
{
return(input.ToList());
}
(int[] h1, int[] h2) = AlgorithmHelpers.SplitInHalf(input.ToArray());
return(Merge(Sort(h1).ToArray(), Sort(h2).ToArray()));
}
public static (List <int> Items, int Inversions) MergeSortInversions(IEnumerable <int> input)
{
if (input == null || input.Count() < 2)
{
return(input.ToList(), 0);
}
(int[] a, int[] b) = AlgorithmHelpers.SplitInHalf(input.ToArray());
(List <int> sortedA, int ai) = MergeSortInversions(a);
(List <int> sortedB, int bi) = MergeSortInversions(b);
return(Merge(sortedA.ToArray(), sortedB.ToArray(), ai + bi));
}