@array = (2 ,4, 3, 8, 9, 12, 13, 20, 18, 7 )
@sortedarray = (20, 18, 13, 12, 9, 8, 7, 4, 3, 2)
After replacement (A, A, -, -, -, -, -, -, -, -, B, B)
@finalarray = (B, -, B, -, -, -, -, A, A , -)