// The algorithm builds a heap. It then repeatedly swaps the first
// and last items in the heap, and rebuilds the heap excluding the last item.
// O(N log N)
public static void HeapSort <T>(this T[] arr)
where T : IComparable <T>
{
Heap <T> heap = new Heap <T>(arr.Length);
// N log N
foreach (T item in arr)
{
heap.Push(item);
}
// + N log N
for (int i = 0; i < arr.Length; i++)
{
arr[i] = heap.Pop();
}
}
