levenshtein.rb

#!/usr/bin/env ruby
# coding: utf-8

def levenshtein(a, b)
  (0..a.size).inject([[*0..b.size+1]]){|d, i|
    d << (0..b.size).inject([i+1]){|_d, j|
      _d << [
        d[i][j+1] + 1,
        _d[j] + 1,
        d[i][j] + (a[i]==b[j] ?0:1)
      ].min
    }
  }[-1][-1]
end

puts levenshtein(ARGV[0], ARGV[1])