We have already seen that a Heap can store a set of items and return
the smallest one, in *O(log(n))* time per item.

Therefore, an easy way to sort would be to put all the items into a
heap, then remove items one at a time with ` deleteMin` and put
them into the output array.

The problem with this easy method is that it uses an extra array. However, we can do it using the original array:

- Make the original array into a max heap. This can be done in
*O(n)*time. - For the size of the heap,
- Remove the largest item from the heap. This makes the heap smaller,
so that there is a hole at the end of the heap.
- Put the largest item into the hole.

- Remove the largest item from the heap. This makes the heap smaller,
so that there is a hole at the end of the heap.

This gives a sort in *O(n · log(n))* time. Heapsort is in-place,
but not stable.