From: Jen <fluffy_bunny_1988@...>
Date: 2011-03-16T07:23:29+09:00
Subject: Making an array of arrays?

Hello,

I'm trying to make an array of arrays, but my code is not behaving as I 
expect.

Specifically I am trying to make an array to hold Sudoku boards (each 
board is a 2D array). I am doing this because I am trying to use genetic 
programming techniques to attempt to solve a simple sudoku puzzle.

Here is the code I am using to copy the @board array in to @offspring:

#When the for loop can take the value from pop must subtract 1 from it 
to avoid having to do nasty index manipulation on the array
i = 0
#Define an offspring array that will hold the copies of the @board array
@offspring = Array.new
for i in 0..3
@offspring[i] = @board.clone
end
#For debugging
#puts @offspring.length
end

I expected that the code above would populate the @offspring array, so 
that each element contained an array of arrays (a copy of @board).

My aim is to itterate through @offspring, and replace each "_" character 
in @offspring with a random number. Note for testing purposes I am 
trying to  replace all instances of "_" with 9.

The code to do this is here:

#All empty cells in offspring can be populated with rand nums in one go
#Then run the 'solved' method again
def find_empty
##Loop through @offspring and where ever there is "_" put a random number.
i = 0
for i in 0..80
if @offspring[i] = "_"
then @offspring[i]= 9
end
#For debugging with the test puzzle
puts @offspring.inspect
end

@offspring.inspect simply prints out a line of 9s. I have tried 
replacing 'for i in 0..80' with 'for i in 0..4', as I felt the number of 
itterations should reflect the size of the offspring array. This doesn't 
return the result I want.

I am now stuck. I know what I want to achieve, but haven't got the logic 
quite right. I'm guessing I am dealing with 3D arrays, but am starting 
to confuse myself now.

Note I am using a test puzzle. It only contains one "_" char, which must 
be replaced with 3 for the puzzle to be solved.

Any suggestions that can enable me to achieve what I want are greatly 
appreciated.

Many thanks in advance,
Jen.