From: Adam Shelly <adam.shelly@...>
Date: 2006-01-20T11:06:39+09:00
Subject: Re: Ruby Quiz #62

On 1/19/06, James Edward Gray II <james@grayproductions.net> wrote:
> This version of the code seems to fix at least this case:

There's a small bug in your code, James:
If you pass a box that fits the trunk exactly, you get an exception.
The culprit is this line from #try_adding box

>        # score the remaining open space
>        score = rows[1..-2].map { |row| row[/_(_+)/, 1] }.compact.
>                            map { |open| open.size }.inject { |sum, n|
> sum + n }

score is nil if there is no open space.  you need to make it ...
inject(0) {|sum,n| ...

You've got a good heuristic, but it still makes mistakes.  Here's a
case that needs an extra trunk with your solution:

C:\ruby\RUBYRE~1\Main\Quiz>more 662.txt
6x6
2x3 2x2 3x6 1x6 4x1 4x4

C:\ruby\RUBYRE~1\Main\Quiz>pack.rb 662.txt

######
######
######
______
######
______

####__
####__
####__
####__
______
####__

###_##
###_##
______
______
______
______

Those 2 in the last trunk ought to be where in the 1st trunk, and the
1x6 should be in the 2nd trunk.  I think it's impossible to have a
perfect solution without an incredibly deep search.

On a totally unrelated note - I discovered something odd when working
on this solution:
irb(main):010:0> r=1..9
=> 1..9
irb(main):011:0> r.last
=> 9
irb(main):012:0> r.include? r.last
=> true
irb(main):013:0> r=1...9
=> 1...9
irb(main):014:0> r.last
=> 9
irb(main):015:0> r.include? r.last
=> false

I really expected (1...9).last to return 8.   I guess this is just
another way ranges are screwy.

-Adam