Test on color code II

	def safe?(col, others)
	others.each_with_index do |c, r|
	return false if col == c or (col - c).abs == (others.size - r).abs
	end
	end
	def solve(n, solutions = [], cols=[])
	return solutions.push(cols) unless cols.size < n
	n.times { |col| solve(n, solutions, cols + [col]) if safe?(col, cols) }
	return solutions
	end
	def show_solutions(n)
	solutions = solve(n)
	puts "There are #{solutions.size} solutions for n = #{n}."
	for cols in solutions
	puts '', cols.map { |c| (0...n).map { |i| i == c ? '$ ' : '0 ' }.join }
	end
	end
	show_solutions(6)

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