Gem::Text#levenshtein_distance

# File tmp/rubies/ruby-3.0.5/lib/rubygems/text.rb, line 54
def levenshtein_distance(str1, str2)
  s = str1
  t = str2
  n = s.length
  m = t.length

  return m if (0 == n)
  return n if (0 == m)

  d = (0..m).to_a
  x = nil

  str1.each_char.each_with_index do |char1,i|
    e = i + 1

    str2.each_char.each_with_index do |char2,j|
      cost = (char1 == char2) ? 0 : 1
      x = min3(
           d[j + 1] + 1, # insertion
           e + 1,      # deletion
           d[j] + cost # substitution
         )
      d[j] = e
      e = x
    end

    d[m] = x
  end

  return x
end