Rebuilding binary search trees

At the exercise BUSCE is described a binary search tree with its
preorder traversal, which includes a -1 for each leaf. But, in fact, it
is not necessary to include the -1’s in the preorder of a search tree to
be able to rebuild it.

Write a program that reads a sequence of binary search tree described
with their preorder traversal with out -1’s. For each tree, it must
write its postorder traversal.

Input

Input consists of a sequence of description of binary trees as it is
explained at REREC, with an exception: The -1 corresponding to the
leaves are omitted. Suppose that trees are search trees and that its
elements are natural numbers.

Output

For each tree of the input, your program must print a line with the
postorder traversal of the tree. Each element must be preceded by a
space.

Problem information

Author: Unknown
Translator: Carlos Molina

Generation: 2026-01-25T10:30:49.743Z

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