Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

The name of the postorder traversal comes from the fact that this traversal method
will visit a node v after it has visited all the other nodes in the subtree rooted at v.
(See Figure 7.8.)
Figure 7.8:
of Figure 7.6.
Postorder traversal of the ordered tree
The analysis of the running time of a postorder traversal is analogous to that of a
preorder traversal. (See Section 7.2.2.) The total time spent in the nonrecursive
portions of the algorithm is proportional to the time spent visiting the children of
each node in the tree. Thus, a postorder traversal of a tree T with n nodes takes O(n)
time, assuming that visiting each node takes O(1) time. That is, the postorder
traversal runs in linear time.
As an example of postorder traversal, we show a Java method
toStringPostorder in Code Fragment 7.12, which performs a postorder
traversal of a tree T. This method prints the element stored at a node when it is
visited.
Code Fragment 7.12: Method
toStringPostorder(T, v) that performs a
postorder printing of the elements in the subtree of
node v of T. The method implicitly calls toString on
elements, when they are involved in a string
concatenation operation.
392