lib/did_you_mean/levenshtein.rb
def distance(str1, str2)
      n = str1.length
      m = str2.length
      return m if n.zero?
      return n if m.zero?

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

      # to avoid duplicating an enumerable object, create it outside of the loop
      str2_codepoints = str2.codepoints

      str1.each_codepoint.with_index(1) do |char1, i|
        j = 0
        while j < m
          cost = (char1 == str2_codepoints[j]) ? 0 : 1
          x = min3(
            d[j+1] + 1, # insertion
            i + 1,      # deletion
            d[j] + cost # substitution
          )
          d[j] = i
          i = x

          j += 1
        end
        d[m] = x
      end

      x
    end
def distance(str1, str2)
      n = str1.length
      m = str2.length
      return m if n.zero?
      return n if m.zero?

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

      # to avoid duplicating an enumerable object, create it outside of the loop
      str2_codepoints = str2.codepoints

      str1.each_codepoint.with_index(1) do |char1, i|
        j = 0
        while j < m
          cost = (char1 == str2_codepoints[j]) ? 0 : 1
          x = min3(
            d[j+1] + 1, # insertion
            i + 1,      # deletion
            d[j] + cost # substitution
          )
          d[j] = i
          i = x

          j += 1
        end
        d[m] = x
      end

      x
    end
:nodoc:
 This code is based directly on the Text gem implementation
 Copyright (c) 2006-2013 Paul Battley, Michael Neumann, Tim Fletcher.

 Returns a value representing the "cost" of transforming str1 into str2