#!/usr/bin/ruby

class Combination

	def initialize(input)
		@array = input.split("")
		@hits = 0
	end

	def fac(int)
		result = 1
		1.upto(int) { |i| result*=i}
		return result
	end

	def recurse(an_array = @array, a_string = "")
		if an_array.length < 2 then
			puts a_string + an_array.to_s
			@hits += 1
		else
			index = 0
			temp_array = []
			temp_string = ""
			an_array.each do |element|
				temp_string = a_string + element
				temp_array.replace(an_array)
				temp_array[index] = nil
				recurse(temp_array.compact, temp_string)
				index += 1
			end
		end
	end
	
	def validate
		if fac(@array.length) == @hits then
			puts "---------------------"
			puts "Found " + @hits.to_s + ' combinations of "' + @array.to_s + '"'
		else
			puts "---------------------"
			puts "Recursion error, expecting " + fac(@array.length).to_s + " results, but counting " + @hits.to_s
		end
	end
	
end

print "Enter a sequence: "
combo = Combination.new(gets.chomp)
puts "---------------------"
combo.recurse
combo.validate