Sudoku

elegant_sudoku_solver.rb

require 'Benchmark'

class Sudoku
  attr_accessor :puzzle

  def initialize  
    @puzzle = ''
    @game = Array.new(9)
    @game.map! { Array.new(9) }
    9.times do |i|
      9.times do |j|
        @game[i][j] = nil
      end
    end
  end

  def file_read name
    f = File.open(name, "r")
    while(line = f.gets)
      @puzzle << line
    end
  end

  def to_s
    puzzle = ''
    9.times do |i|
      9.times do |j|
        puzzle << ' ' if j % 3 == 0 and j != 1
        if @game[i][j] == nil
          puzzle << "-"  
        else
          puzzle << @game[i][j].to_s
        end
      end
      puzzle << "\n"
      puzzle << "\n" if (i + 1) % 3 == 0
    end
    return puzzle
  end

  def set(val)
    i=0
    val = val.delete("\n")
    9.times do |row|
      9.times do |col|
        x = val[i].to_i
        x = nil if x == 0
        @game[row][col] = x
        i+=1
      end
    end
  end

  def solve    
    9.times do |r|
      9.times do |c|
        next if @game[r][c]

        1.upto(9) do |v|
          # check -|-
          next unless 9.times { |i| break if @game[i][c] == v || @game[r][i] == v }
          
          # check 3x3
          next unless 3.times do |i|
            break unless 3.times do |j|
                break if @game[i + r / 3 * 3][j + c / 3 * 3] == v
              end
            end
          
          @game[r][c] = v

          if solve
            return true
          else
            @game[r][c] = nil  # backtracking
          end     

        end      
        return false
      end
    end
    return true
  end

end

sudo = Sudoku.new
sudo.file_read("tests.txt")
sudo.set(sudo.puzzle)
print sudo.to_s

Benchmark.bm do |x|
  x.report("Sudoku:") { sudo.solve }
end

sudo.solve ? (print sudo.to_s) : "brak rozwiazania"