Is an array that is sorted in decreasing order a max-heap?
Every array which is sorted in ascending order is always a min heap
And Every array which is sorted in descending order is always a max heap .
i think max sorted in ascending order.....!!!!!!!!check out https://stackoverflow.com/questions/41212072/ascending-and-descending-heapsort
Yes, they can. You can read about this in 'Introduction to Algorithms' (by Charles E. Leiserson, Clifford Stein, Thomas H. Cormen, and Ronald Rivest). According to the definition of binary heaps in Wikipedia:
All nodes are either [greater than or equal to](max heaps) or [less than or equal to](min heaps) each of its children, according to a comparison predicate defined for the heap.