Implementing quicksort algorithm

Question

I found quicksort algorithm from this book

This is the algorithm

QUICKSORT (A, p, r)
i         


        

Answer 1

Just in case you want some shorter code for Quicksort:

    IEnumerable QuickSort(IEnumerable i)
    {
        if (!i.Any())
            return i;
        var p = (i.First() + i.Last) / 2 //whichever pivot method you choose
        return QuickSort(i.Where(x => x < p)).Concat(i.Where(x => x == p).Concat(QuickSort(i.Where(x => x > p))));
    }

Get p (pivot) with whatever method is suitable of course.