start:  A = [16 4 10 14 7 9 3 2 8 1]

calling MAX-HEAPIFY(A, 2)
  MAX-HEAPIFY(A, 2): A[2]=4, left A[4]=14, right A[5]=7 -> largest is index 4
    swap, giving A = [16 14 10 4 7 9 3 2 8 1]
  MAX-HEAPIFY(A, 4): A[4]=4, left A[8]=2, right A[9]=8 -> largest is index 9
    swap, giving A = [16 14 10 8 7 9 3 2 4 1]
  MAX-HEAPIFY(A, 9): A[9]=4, no left child, no right child -> largest is index 9
    node 9 already dominates its children: stop

result: A = [16 14 10 8 7 9 3 2 4 1]
valid max-heap: yes
