資料結構與演算法(A)

(5 points) There is a binary tree stored in an array as:

$T[] = \{+, a, *, null, null, -, d, null, null, null, null, b, c\},$

in which $T[i]$ is the parent of $T[2i+1]$ and $T[2i+2]$, where $i$ is an index and $null$ means there is no element in the slot. What is its postorder traversal result?