Returns a value representing the “cost” of transforming str1 into str2.
# File railties/lib/rails/command/spellchecker.rb, line 20
def levenshtein_distance(str1, str2) # :doc:
s = str1
t = str2
n = s.length
m = t.length
return m if 0 == n
return n if 0 == m
d = (0..m).to_a
x = nil
# avoid duplicating an enumerable object in the loop
str2_codepoint_enumerable = str2.each_codepoint
str1.each_codepoint.with_index do |char1, i|
e = i + 1
str2_codepoint_enumerable.with_index do |char2, j|
cost = (char1 == char2) ? 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
x
end
