# agarie/measurable

lib/measurable/levenshtein.rb

### Summary

A
45 mins
###### Test Coverage
``````module Measurable
module Levenshtein

# call-seq:
#     levenshtein(u, v) -> Integer
#
# Give the edit distance between two binary sequences +u+ and +v+ where each
# edit (insertion, deletion, substitution) required to change on into the
# other increments the total distance.
#
# For example:
#   levenshtein('kitten', 'sitting') == 3
#
# Because
# 1. kitten -> sitten (substitution "s" for "k")
# 2. sitten -> sittin (substitution "i" for "e")
# 3. sittin -> sitting (insertion of "g" at the end)
#
# See: http://en.wikipedia.org/wiki/Levenshtein_distance
#
# Arguments:
# - +u+ -> Array or String.
# - +v+ -> Array or String.
# Returns:
# - Integer value representing the Levenshtein distance between +u+ and +v+.
#
def levenshtein(u, v)
return 0 if u == v
return u.size if v.size == 0
return v.size if u.size == 0

matrix = Array.new(u.size+1) { (0..v.size).to_a }

if v.size < u.size
u, v = v, u
end

(1..u.size).each do |i|
(1..v.size).each do |j|
if u[i] == v[j]
matrix[i][j] = matrix[i-1][j-1]
else
matrix[i][j] = [
matrix[i-1][j] + 1,   # deletion
matrix[i][j-1] + 1,   # insertion
matrix[i-1][j-1] + 1, # substitution
].min
end
end
end

matrix[u.size][v.size]
end
end

extend Measurable::Levenshtein
end``````