Measure the distance between two strings with Ruby?

Question

Can I measure the distance between two strings with Ruby?

I.e.:

compare('Test', 'est') # Returns 1
compare('Test', 'Tes') # Returns 1
compare('Test', 'Tast') # Returns 1
compare('Test', 'Taste') # Returns 2
compare('Test', 'tazT') # Returns 5

Answer

I found this for you:

def levenshtein_distance(s, t)
  m = s.length
  n = t.length
  return m if n == 0
  return n if m == 0
  d = Array.new(m+1) {Array.new(n+1)}

  (0..m).each {|i| d[i][0] = i}
  (0..n).each {|j| d[0][j] = j}
  (1..n).each do |j|
    (1..m).each do |i|
      d[i][j] = if s[i-1] == t[j-1]  # adjust index into string
                  d[i-1][j-1]       # no operation required
                else
                  [ d[i-1][j]+1,    # deletion
                    d[i][j-1]+1,    # insertion
                    d[i-1][j-1]+1,  # substitution
                  ].min
                end
    end
  end
  d[m][n]
end

[ ['fire','water'], ['amazing','horse'], ["bamerindos", "giromba"] ].each do |s,t|
  puts "levenshtein_distance('#{s}', '#{t}') = #{levenshtein_distance(s, t)}"
end

That's awesome output: =)

levenshtein_distance('fire', 'water') = 4
levenshtein_distance('amazing', 'horse') = 7
levenshtein_distance('bamerindos', 'giromba') = 9

Source: http://rosettacode.org/wiki/Levenshtein_distance#Ruby