如何在无序数组中找到第K个最大元素？

Question

我有这段代码，可以找到一个无序数组中第k个最小的元素。我想知道什么需要更改，以便它可以找到数组中第K个最大的元素。例如，如果我放2，它将在数组中找到第二大元素

public static double FindTheKSmallest(double[] tab, int find)
    {
        //the method is searching for the k-th SMALLEST element in the array and returns the result as tab[k]: smallest element (find=1) is tab[0], second smallest (isci=2) is tab[1]...
        int k = find - 1;
        if (tab == null || tab.Length <= k)
            throw new Exception("This table doesn't exist or has incorrect parameters");
        int fromWhere = 0, toEnd = tab.Length - 1;
        while (fromWhere < toEnd)
        {
            int leftBorder = fromWhere;
            int rightBorder = toEnd;
            double Middle = tab[(leftBorder + rightBorder) / 2];
            // We repeat until the left and right border meet
            while (leftBorder < rightBorder)
            {
                if (tab[leftBorder] >= Middle)
                {
                    // We move the bigger numbers to the right border
                    double tmp = tab[rightBorder];
                    tab[rightBorder] = tab[leftBorder];
                    tab[leftBorder] = tmp;
                    rightBorder--;
                }
                else
                {
                    //value is smaller than the pivot, so we ignore it
                    leftBorder++;
                }
            }
            // if we went through the middle, we go one step back
            if (tab[leftBorder] > Middle)
                leftBorder--;
            //indeks leftBorder is at the end of the first k elements
            if (k <= leftBorder)
            {
                toEnd = leftBorder;
            }
            else
            {
                fromWhere = leftBorder + 1;
            }
        }
        return tab[k];
    }

static void Main(string[] args)
    {
        double[] tab = { 3, 5, 8, 1, 9, 6, 5 };
        Console.WriteLine(FindTheKSmallest(tab, 2)); //it should be  8
        Console.ReadKey();
    }