From: James Edward Gray II <james@...>
Date: 2006-06-16T06:05:58+09:00
Subject: Re: Newbie program

On Jun 15, 2006, at 1:34 PM, Logesh Pillay wrote:

> I'd appreciate suggestions how to improve it.

Well, I've tried to Rubify the code a bit.  I did these things;

* Stopped defining methods in methods.
* Used a class.
* Switched the global variables to instance variables.
* Used upto() iterators.
* Got rid of print().
* Made stillgood() method name more Rubish.
* Added the application code test at the end.

The thing I think you should still do:

* Pick more meaningful variable names than @n and k.

Here's the code.

class NQueens
   def initialize
     @n = 8
     @board = [nil] * (@n + 1)
   end

   def choose(k)
     if k > @n
       puts @board.join
     else
       1.upto(@n) do |i|
         @board[k] = i
         choose(k + 1) if k == 1 or still_good?(k)
       end
     end
   end

   def still_good?(k)
     1.upto(k - 1) do |i|
       return false if (@board[k] == @board[i]) or
                       (k-i == (@board[k] - @board[i]).abs)
     end
     true
   end
end

if __FILE__ == $PROGRAM_NAME
   NQueens.new.choose(1)
end

Hope that helps.

James Edward Gray II