Heapsort Algorithm using min-heap

Question

When I implement heapsort using a min-heap it sorts the array from largest to smallest. Is this the desired output for a heapsort using

Answer 1

Normally you use a max-heap to sort in ascending order, because its easier. Using a max-heap, you 'float' the max to the front, and build the sorted list from the back.

If you want to use a min-heap to sort in ascending order, you have to build it backwards. (ie the lowest is the last index ). Otherwise you will be churning your heap.

start 18 70 6 13 12 55 
min-heap(backwards) -> 18 70 55 13 12 6
then
swap  6 w 18 -> 6, 70 55 13 12 18 -> sink 18 -> 70 55 13 18 12
swap 12 w 70 -> 6 12, 55 13 18 70 -> sink 70 -> 55 70 18 13
swap 13 w 55 -> 6 12 13, 70 18 55 -> sink 55 -> 70 55 18
swap 18 w 70 -> 6 12 13 18, 55 70 -> sink 70 -> 70 55
swap 55 w 70 -> 6 12 13 18 55, 70 
done