jaccard.cr

def one_way_distance(string_a, string_b)
  score = 0
  against = 0
  (0..string_a.size-1).each do |idx|
    (idx..string_a.size-1).each do |len|
      if !string_b.index(string_a[idx, len-idx+1], 0).nil?
        score += (len-idx+1)*2
      else
        against += 1
      end
    end
  end
  return {score: score, against: against}
end

def jaccard_string_similarity(string_a, string_b)
  score_1 = one_way_distance(string_a, string_b)
  score_2 = one_way_distance(string_b, string_a)
  if score_1[:score] == score_2[:score] & score_2[:score] == 0
    return 0
  else
    return (score_1[:score] + score_2[:score])/(score_1[:score] + score_2[:score] + score_1[:against] + score_2[:against])
  end
end


puts jaccard_string_similarity("batman", "banana") # 0.5970149253731343