This code is based directly on the Text gem
implementation Returns a value representing the “cost” of transforming
str1 into str2
# File lib/rubygems/text.rb, line 31
def levenshtein_distance str1, str2
s = str1
t = str2
n = s.length
m = t.length
max = n/2
return m if (0 == n)
return n if (0 == m)
return n if (n - m).abs > max
d = (0..m).to_a
x = nil
n.times do |i|
e = i+1
m.times do |j|
cost = (s[i] == t[j]) ? 0 : 1
x = [
d[j+1] + 1, # insertion
e + 1, # deletion
d[j] + cost # substitution
].min
d[j] = e
e = x
end
d[m] = x
end
return x
end