/// <summary>
/// Rearranges the array so that a[k]} contains the kth smallest key;
/// a[0] through a[k-1] are less than (or equal to) a[k];
/// a[k+1] through a[n-1] are greater than (or equal to) a[k].
/// </summary>
/// <param name="a">the array</param>
/// <param name="k">the rank of the key</param>
/// <returns>the key of rank k}</returns>
public static T Select(T[] a, int k)
{
if (k < 0 || k >= a.Length)
{
throw new ArgumentOutOfRangeException(nameof(k), k, "out of bounds");
}
StdRandom.shuffle(a);
int lo = 0, hi = a.Length - 1;
while (hi > lo)
{
int i = partition(a, lo, hi);
if (i > k)
{
hi = i - 1;
}
else if (i < k)
{
lo = i + 1;
}
else
{
return(a[i]);
}
}
return(a[lo]);
}
/// <summary>
/// Rearranges the array in ascending order, using the natural order.
/// </summary>
/// <param name="a">the array to be sorted</param>
public static void Sort(T[] a)
{
StdRandom.shuffle(a);
sort(a, 0, a.Length - 1);
Debug.Assert(SortingHelper <T> .isSorted(a));
}