TARGET = "Hello, world!"

class Array
  def pos_of_min
    min = 999999999999999
    pos = nil
    self.each_with_index do |a, i|
      if a < min
        pos = i
        min = a
      end
    end
    pos
  end
end

def random_string
  (1..TARGET.size).collect {|x| 32 + rand(94) }
end

def distance(chromosome)
  chromosome.zip(TARGET.unpack("c*")).inject(0) {|sum, a| sum += (a[1]-a[0]) ** 2}
end

def mutate(chromosome)
  mutated = []
  chromosome.each_with_index do |a, i|
    mutated << if (a-TARGET[i]).abs > 0
      a + rand(7) - 3
    else
      a
    end
  end
  mutated
end

def iterate(chromosome)
  candidates = 100.times.collect {mutate(chromosome)}
  scores = candidates.collect {|c| distance(c)}
  candidates[scores.pos_of_min]
end

candidate = random_string
puts "starting with: " + candidate.pack("c*")
50.times do |i|
  candidate = iterate(candidate)
  puts sprintf("%03d ", i+1) + candidate.pack("c*")
end