Inserting 6, 8, 4, 7, 2, 3, 9, 1, 5 using buildHeap.
if indexing from 0: loop over interval [⌊N/2⌋ − 1, 0].
if indexing from 1: loop over interval [⌊N/2⌋, 1].

initial state before starting buildheap.
[6, 8, 4, 7, 2, 3, 9, 1, 5]
        6
    8       4
  7   2   3   9
 1 5

after executing buildHeap(4)
[6, 8, 4, 1, 2, 3, 9, 7, 5]
        6
    8       4
  1   2   3   9
 7 5

after executing buildHeap(3)
[6, 8, 3, 1, 2, 4, 9, 7, 5]
        6
    8       3
  1   2   4   9
 7 5

after executing buildHeap(2) iteration 1
[6, 1, 3, 8, 2, 4, 9, 7, 5]
        6
    1       3
  8   2   4   9
 7 5

after executing buildHeap(2) iteration 2
[6, 1, 3, 5, 2, 4, 9, 7, 8]
        6
    1       3
  5   2   4   9
 7 8

after executing buildHeap(1) iteration 1
[1, 6, 3, 5, 2, 4, 9, 7, 8]
        1
    6       3
  5   2   4   9
 7 8

after executing buildHeap(1) iteration 2
[1, 2, 3, 5, 6, 4, 9, 7, 8]
        1
    2       3
  5   6   4   9
 7 8