Sudoku Solver works for all boards from beginner to advanced that don't require guessing. Yeeuh boi.

SudokuSolver.rb

class Sudoku

#RKelley is boss.

def initialize(board_string)

  board_string_array = board_string.split('')

  @board = Array.new(9){Array.new(9)}

  @board.each_index do |row|
    @board[row].each_index do |column|
      @board[row][column] = board_string_array.shift.to_i
      if @board[row][column] == 0
        @board[row][column] = (1..9).to_a
      end
    end
  end
end


  def solve!
    @solved_board = false


    return @board if @solved_board == true


    until @solved_board do
      check_answers
      col_solve
      box_solve
      print_board
      solved?
      sleep 0.5
    end
    @board
  end
  
  def print_board
    p @board

  end

  def solved?

    @board.each do |row|
      row.each do |element|
        if element.class == Array then 
          return false
        end
      end
    end
    @solved_board = true
  end


    def check_answers

    @board.map! do |row|
      row.map do |element|
        if element.class == Array
          element -= row
          element.length == 1 ? element[0] : element
        else
          element
        end
      end
    end
    @board
  end


  def col_solve
    @board = @board.transpose

    check_answers

    @board = @board.transpose
  end

  
  def box_solve

    @board = [@board[0][0..2] + @board[1][0..2] + @board[2][0..2], @board[0][3..5] + @board[1][3..5] + @board[2][3..5], @board[0][6..8] + @board[1][6..8] + @board[2][6..8], @board[3][0..2] + @board[4][0..2] + @board[5][0..2], @board[3][3..5] + @board[4][3..5] + @board[5][3..5], @board[3][6..8] + @board[4][6..8] + @board[5][6..8], @board[6][0..2] + @board[7][0..2] + @board[8][0..2], @board[6][3..5] + @board[7][3..5] + @board[8][3..5], @board[6][6..8] + @board[7][6..8] + @board[8][6..8]]
    
    check_answers

    @board = @board[0][0..2] + @board[1][0..2] + @board[2][0..2], @board[0][3..5] + @board[1][3..5] + @board[2][3..5], @board[0][6..8] + @board[1][6..8] + @board[2][6..8], @board[3][0..2] + @board[4][0..2] + @board[5][0..2], @board[3][3..5] + @board[4][3..5] + @board[5][3..5], @board[3][6..8] + @board[4][6..8] + @board[5][6..8], @board[6][0..2] + @board[7][0..2] + @board[8][0..2], @board[6][3..5] + @board[7][3..5] + @board[8][3..5], @board[6][6..8] + @board[7][6..8] + @board[8][6..8]
    @board
  end

end


# game = Sudoku.new("619030040270061008000047621486302079000014580031009060005720806320106057160400030")
# game = Sudoku.new("302609005500730000000000900000940000000000109000057060008500006000000003019082040")
game = Sudoku.new("370000001000700005408061090000010000050090460086002030000000000694005203800149500")



# Remember: this will just fill out what it can and not "guess"

p game.solve!

# p game.board

# p game.row_solve_col_solve

# p game.row_solve

# p game.col_solve

# p game.solve!

# game.board

#p game.box_solve