[QUIZ] Bracket Packing (#78) (2 solutions)

ruby-talk
1

Here is my solution to the first option of the quiz, which is simply to detect if there is a problem. It makes use of the allowed assumption that only one packaging character would be omitted in incorrect input. So the underlying algorithm is to make sure there are an even number of combined "("s and ")"s (and the same goes for the other two types of packaging). The String#count method does much of the heavy lifting.

["()", "{}", "[]"].each { |symbol_pair| exit(1) if 0 != ARGV[0].count(symbol_pair) % 2 }
puts ARGV[0]

Here's another solution which repeatedly substitutes any of "(B)", "[B]", "{B}", or "BB" with "B". In other words it just unwraps and combines brackets. When all is said an done, one bracket should be left if the wrapping description was correct.

description = ARGV[0].dup
while description.gsub!(/\(B\)|\[B\]|{B}|BB/, "B")
   #empty
end
exit(1) unless description == "B"
puts ARGV[0]

Eric

2

Just thinking out loud here, but how does this fair with inputs like:

")B(" or "B()"

?

James Edward Gray II

···

On May 7, 2006, at 1:36 PM, Eric I. wrote:

Here is my solution to the first option of the quiz, which is simply to detect if there is a problem. It makes use of the allowed assumption that only one packaging character would be omitted in incorrect input. So the underlying algorithm is to make sure there are an even number of combined "("s and ")"s (and the same goes for the other two types of packaging). The String#count method does much of the heavy lifting.

["()", "{}", ""].each { |symbol_pair| exit(1) if 0 != ARGV[0].count(symbol_pair) % 2 }
puts ARGV[0]

3

Huhu James,
I think ")B(" or "B()" are not valid outputs, because the program only
misses off brackets.

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

Please tell me if I misinterpreted the machine.

Kind regards.
Robert

James Edward Gray II schrieb:

···

Just thinking out loud here, but how does this fair with inputs like:

")B(" or "B()"

?

James Edward Gray II

4

Right. I think that's pretty much what everyone agreed on.

James Edward Gray II

···

On May 11, 2006, at 12:13 PM, Robert Retzbach wrote:

Huhu James,
I think ")B(" or "B()" are not valid outputs, because the program only
misses off brackets.

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

Please tell me if I misinterpreted the machine.