From: Ruby Quiz <james@...>
Date: 2006-05-05T20:46:40+09:00
Subject: [QUIZ] Bracket Packing (#78)

The three rules of Ruby Quiz:

1.  Please do not post any solutions or spoiler discussion for this quiz until
48 hours have passed from the time on this message.

2.  Support Ruby Quiz by submitting ideas as often as you can:

http://www.rubyquiz.com/

3.  Enjoy!

Suggestion:  A [QUIZ] in the subject of emails about the problem helps everyone
on Ruby Talk follow the discussion.  Please reply to the original quiz message,
if you can.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

by Ross Bamford

The BigCo Bracket Company, one of the world's largest suppliers of brackets,
hinges and fittings, has lately been experiencing problems in it's manufacturing
division, with a large number or brackets lost or broken in transit owing to
faulty packaging at the end of the line.

Investigations into the cause of the problem have led engineers to an ancient
COBOL program controlling the packaging machinery. This program is responsible
for selecting the type of packaging a given bracket should be shipped in, based
on input from an array of sensors on the production line. It then sends a 
description of the package to the packager itself, which packs the bracket and
sends it on to shipping. The description is a simple text string, made up of
brackets with the following format:

	(B)     - Bracket in a soft wrapping
	[B]     - Bracket in a cardboard box
	{B}     - Bracket in a wooden box

Often, brackets have multiple layers of packaging for protection, for example:

	{(B)}   - Soft-wrapped bracket in a wooden box
	[{B}]   - Wooden-boxed bracket with cardboard outer
	
	[{(B)}{(B)(B)}] - Wooden boxed single and double bracket packs with soft
	                  inner wrap, in cardboard outer. 

Now, the problem is that this venerable program has for some reason begun to
output malformed packaging descriptions, occasionally missing off a bracket, for
example:

	[{(B}{(B)(B)}]

or:

	{(B)}{(B)(B)}]

After a fruitless search for someone with the skills to fix this problem, the
engineers changed tack and called you in to fix the problem from the outside.

	What needs to be done?
	======================

Basically, the plan is to insert another computer between the controller and the
packer, upon which will run your program. The engineers can handle the
integration with their systems - they just need you to write a slick bit of Ruby
code to validate the packaging descriptions as they're passed in. You've been
given two choices:

	* Check the description, and return exitcode indicating it's okay (0)
	  or bad (1). If correct, you should also print the description to stdout.
	  If it's bad, the system can then force the controller to try again.
	
	* Fix the description, if possible, and print it to stdout. The system
	  will then pass the fixed code to the packer.