Levenshtein Distance in Ruby using matrix

levenshtein_distance.rb

# Levenshtein Distance
# implementation given at http://en.wikipedia.org/wiki/Levenshtein_distance
# This file is in the public domain.

require 'matrix'

def levenshtein_distance str1, str2
  str1_len   = str1.size
  str2_len   = str2.size
  width      = str1_len + 1
  height     = str2_len + 1

  d = Matrix.zero(height, width)

  width.times  { |i| d.send(:[]=, 0, i, i) }
  height.times { |i| d.send(:[]=, i, 0, i) }

  str1_len.times do |x|
    str2_len.times do |y|
      cost = str1[x] == str2[y] ? 0 : 1
      d.send(:[]=, (1+y), (1+x), [
        d[y, (1+x)] + 1,
        d[(1+y), x] + 1,
        d[y, x]     + cost
      ].min)
    end
  end

  return d[str2_len, str1_len]
end