Time Limit: 2 Seconds
Memory Limit: 65536 KB
Little Valentine liked playing with binary trees very much. Her favorite game
was constructing randomly looking binary trees with capital letters in the nodes.
This is an example of one of her creations:
/ \ \
/ \ \
A C G
To record her trees for future generations, she wrote down two strings for
each tree: a preorder traversal (root, left subtree, right subtree) and an inorder
traversal (left subtree, root, right subtree). For the tree drawn above the
preorder traversal is DBACEGF and the inorder traversal is ABCDEFG.
She thought that such a pair of strings would give enough information to reconstruct
the tree later (but she never tried it).
Now, years later, looking again at the strings, she realized that reconstructing
the trees was indeed possible, but only because she never had used the same
letter twice in the same tree.
However, doing the reconstruction by hand, soon turned out to be tedious.
So now she asks you to write a program that does the job for her!
The input will contain one or more test cases.
Each test case consists of one line containing two strings preord and inord,
representing the preorder traversal and inorder traversal of a binary tree.
Both strings consist of unique capital letters. (Thus they are not longer than
Input is terminated by end of file.
For each test case, recover Valentine's binary tree and print one line containing
the tree's postorder traversal (left subtree, right subtree, root).
Source: University of Ulm Local Contest 1997