How do I define a dynamic Matrix or

Hello Team,

On my quest to learn Ruby, I implemented a known algorithm to solve an
odd
nXn magic square.
I tested my code using a 3x3 and a 5x5 magic squares.
The problem that I am having is that I hard-code the initialization
matrix.
In other words, if it is a 3x3 I define:

mm = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

For a 5 x 5 I define :

mm = [[0,0,0, 0, 0], [0,0,0, 0, 0], [0,0,0, 0,
0],[0,0,0,0,0],[0,0,0,0,0]]

I want to be able to solve any size odd magic square. To do so, I need
to be
able to define my matrix dynamically and on demand.
Can anyone tell me how to do that?

Attached is my current code. Please feel free to criticize it and make
recommendations. My disclaimer: I am a Ruby apprentice.

Thank you

Victor

#!/usr/local/bin/ruby -d -W0

def mag(size)
r = 0 # row
c = 0 # column
index = 0 # pointer

mm = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

mm = [[0,0,0, 0, 0], [0,0,0, 0, 0], [0,0,0, 0,

0],[0,0,0,0,0],[0,0,0,0,0]]

maxLoop = size * size                           # Magic Square size

1.upto(maxLoop) do |n|

  case
      when n == 1
          c = (size / 2).floor                      # Will keep the

integer part, giving us the center in row 0
mm[c][r] = n # This is:
mm[c][0]
when index >= size
index = 0
r = r + 1
mm[c][r] = n
puts " "
else
c = c + 1
if c >= size
c = 0
end

          r = r -1
          if r < 0
            r = size - 1
          end
          mm[c][r] = n
      end
      index = index + 1

  puts "[#{c}][#{r}] = #{mm[c][r]} "

end # End upto

##############
# Output the matrix    #
##############
puts
0.upto(size -1) do |r|
  0.upto(size -1) do |c|
    print "#{mm[c][r]} "
  end
  puts " "
end

end # End method mag

We start here

p1 = ARGV[0].to_i

mag( p1 )

Hi –

On 28/10/2007, Victor R. [email protected] wrote:

For a 5 x 5 I define :
Thank you

mm = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

mm = [[0,0,0, 0, 0], [0,0,0, 0, 0], [0,0,0, 0,

0],[0,0,0,0,0],[0,0,0,0,0]]

You can just do something like this:

mm = []
size.to_i.times { mm << Array.new(size.to_i,0) }

Incidentally, have you looked into the numerous Matrix/math libs
already defined in Ruby?

– Thomas A.

Victor R. wrote:

…I need to be
able to define my matrix dynamically and on demand.
Can anyone tell me how to do that?

Try this:

#get input:
print 'rows: ’
rows = Integer(gets)
print 'columns: ’
cols = Integer(gets)

#create matrix:
matrix = []
rows.times do |i|
matrix << Array.new(cols, 0)
end

p matrix

Or this:

require ‘matrix’

print "size: "
size = Integer(gets)

m = Matrix.zero(size)
p m

On 10/28/07, Victor R. [email protected] wrote:

For a 5 x 5 I define :
Thank you

mm = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

integer part, giving us the center in row 0
end

  puts " "
end

end # End method mag

We start here

p1 = ARGV[0].to_i

mag( p1 )

irb> odd_matrix_number = 7
irb> my_matrix - Array.new(odd_matrix_number) {
Array.new(odd_matrix_number) {0} }

I’m not sure exactly what is your assignment, but it might be good to
create a MagicSquare object.

My half a cent.

Todd

Many thanks to Thomas and 7stud!
I will try your suggestions!

Thanks again

Victor

On 10/28/07, Todd B. [email protected] wrote:

irb> odd_matrix_number = 7
irb> my_matrix - Array.new(odd_matrix_number) {
Array.new(odd_matrix_number) {0} }

I’m not sure exactly what is your assignment, but it might be good to
create a MagicSquare object.

My half a cent.

Todd

That is supposed to be…

irb> my_matrix = Array.new(odd_matrix_number) {
Array.new(odd_matrix_number) {0} }

(“=” in place of the original “-”)

Somebody get me away from this particular keyboard :slight_smile:

Todd

Thank you gents, for your suggestions and help.

Victor