gistfile1.rb

def hidden_singles
		changed = false
		@groups.each do |group|
			numbers = []
			group.each do |cell|
				numbers = numbers + @possible[cell] unless @possible[cell].size == 1
			end 
			(1..9).to_a.each do |number|
				if numbers.count(number) == 1
					# There is only one spot where number can go in this group. find it!
					group.each do |cell|
						if @possible[cell].member?(number)
							@possible[cell] = [number]
							@cell_groups[cell].each do |group|
								@group_possible[group] = @group_possible[group] - @possible[cell]
								@neiboughs[cell].each do |adjacent|
									if @possible[adjacent].member?(@possible[cell])
										@possible[adjacent] = @possible[adjacent] - @possible[cell]
									end
								end
							end
							changed = true
						end
					end
				end
			end
		end
		changed
	end