sudoku find unique

find_unique.rb

  def find_uniques
    (1..9).each do |set_num|
      map_unique( get_grid(set_num) )
    end
  end

  def map_unique(set)
    last_mapping = 'hello'
    loop do
      (1..9).each do |value|
        val_count = 0
        index = nil
        set.each_with_index do |cell, cell_index|
          if cell.is_a?(Array) && cell.include?(value)
            val_count += 1
            index = cell_index
          end
        end
        set[index] = value if val_count == 1
        val_count = 0
        index = nil
      end
      break if last_mapping == set.join
      last_mapping = set.join
    end
    set
  end