We can use an array-based heap implementation to do an in-place sort of the elements of an array. The trick is to use the same array for backing the heap. In the beginning, we simply insert the elements in the heap from the beginning of the array. We achieve this by replacing the array in the heap, except the one that is passed. Since the heap also uses the space from the beginning, it does not overwrite the elements we are still to insert. While dequeuing the elements, we start saving them from the end of the array, as this is the part that is being freed up by the heap. This means we want the largest element to be dequeued first. This is achieved by simply using a comparator that is the opposite of the one that is passed. We add this static method to our ArrayHeap class:
public static <E> void heapSort(E[] array, Comparator<E> comparator){
ArrayHeap<E> arrayHeap = new ArrayHeap<E>(0, (a,b) -> comparator.compare(b,a));
arrayHeap.store...