Replacing integers with strings within an array Ruby

Question

Currently I have code that looks like:

def sudoku_generator

  @initial_board = [0] * 81

  a = (1..9).sort_by{rand}
  b = (1..9).sort_by{rand}
  c = (1..9).sort_by{rand}

  @initial_board[0..2] = a[0..2]
  @initial_board[9..11] = a[3..5]
  @initial_board[18..20] = a[6..8]
  @initial_board[30..32] = b[0..2]
  @initial_board[39..41] = b[3..5]
  @initial_board[48..50] = b[6..8]

  @initial_board[60..62] = c[0..2]
  @initial_board[69..71] = c[3..5]
  @initial_board[78..80] = c[6..8]

  @initial_board.each_slice(9) do |make_better|
    puts make_better.join(' | ')
  end

end

print sudoku_generator

This returns:

3 | 7 | 9 | 0 | 0 | 0 | 0 | 0 | 0
1 | 5 | 6 | 0 | 0 | 0 | 0 | 0 | 0
2 | 8 | 4 | 0 | 0 | 0 | 0 | 0 | 0
0 | 0 | 0 | 1 | 5 | 8 | 0 | 0 | 0
0 | 0 | 0 | 6 | 7 | 2 | 0 | 0 | 0
0 | 0 | 0 | 3 | 4 | 9 | 0 | 0 | 0
0 | 0 | 0 | 0 | 0 | 0 | 5 | 1 | 3
0 | 0 | 0 | 0 | 0 | 0 | 4 | 8 | 7
0 | 0 | 0 | 0 | 0 | 0 | 6 | 2 | 9

I am trying to find a way to now replace the zeros within this array with underscores "_". Any feedback would be appreciated. Thanks.

Why not do @initial_board = Array.new(81, "_") from the beginning? — sawa
– sawa, Commented Feb 11, 2015 at 22:38

Nick Veys · Accepted Answer · 2015-02-11 22:40:51Z

2

As @sawa suggested in the comments, I'd default the array to '_', but you can always just swap 0 for '_' as you print:

puts make_better.map { |x| x == 0 ? '_' : x }.join(' | ')

answered Feb 11, 2015 at 22:40

Nick Veys

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3 Comments

sawa Over a year ago

You can do x.zero?.

Abraham Chan Over a year ago

May as well use map!

Josh Over a year ago

Thank you all for the quick responses. I learned something today. ;)

shock_one · Accepted Answer · 2015-02-11 23:25:51Z

How about using classes? It'a an object oriented language, right? I guess the method #to_s could have been prettier, though.

class Grid
  SIZE = 3

  def initialize
    @array = Array.new(3) { |line| Array.new(3) { |column| generator.call(line, column) } }
  end

  def generator
    proc { '_' }
  end

  def to_a
    @array
  end
end

class RandomGrid < Grid
  def generator
    @random_numbers ||= (1..9).to_a.shuffle
    proc { @random_numbers.shift }
  end
end


class DiagonalBoard < Grid
  def generator
    proc { |line, column| (line == column ? RandomGrid : Grid).new }
  end

  def to_s
    @array.map do |grids|
      grids.map(&:to_a).transpose.map do |rows|
        rows.flatten.join('|')
      end.join("\n")
    end.join("\n")
  end
end

puts DiagonalBoard.new

Outputs

9|2|8|_|_|_|_|_|_
5|3|7|_|_|_|_|_|_
1|4|6|_|_|_|_|_|_
_|_|_|8|1|5|_|_|_
_|_|_|6|2|9|_|_|_
_|_|_|3|4|7|_|_|_
_|_|_|_|_|_|2|9|1
_|_|_|_|_|_|7|5|6
_|_|_|_|_|_|3|8|4

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