weasel.rb

TARGET = %{METHINKS IT IS LIKE A WEASEL}
CHARS = (('A'..'Z').to_a << ' ')
INITIAL_SEED_STR = ''

28.times { INITIAL_SEED_STR << CHARS.shuffle.first }

def score_for_string str
  score = 0
  target_chars = TARGET.chars

  str.chars.each_with_index do |char, i|
    score += 1 if char == target_chars[i]
  end

  return score
end

def mutate_string! string
  chars = []

  string.chars.each do |char|
    if rand(100) > 95
      chars << CHARS.shuffle.first
    else
      chars << char
    end
  end

  return chars.join
end

def new_generation seed_str
  generation = []
  100.times { generation << mutate_string!(seed_str) }
  return generation
end

def find_highest_scored generation
  return generation.sort_by { |str| score_for_string str }.last
end

i = 0
best = INITIAL_SEED_STR
loop do
  puts "#{i}:\t#{best}"
  i += 1

  break if best == TARGET
  best = find_highest_scored(new_generation(best))
end