Class: String
Instance Method Summary collapse
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#levenshtein(other, ins = 2, del = 2, sub = 1) ⇒ Object
Calculates the levenshtein distance between strings.
Instance Method Details
#levenshtein(other, ins = 2, del = 2, sub = 1) ⇒ Object
Calculates the levenshtein distance between strings. This method was taken from The Ruby Way, 2nd Edition, Hal Fulton, pp. 97-98
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# File 'lib/string/levenshtein.rb', line 5 def levenshtein(other, ins=2, del=2, sub=1) # ins, del, sub are weighted costs return nil if self.nil? return nil if other.nil? dm = [] # distance matrix # Initialize first row values dm[0] = (0..self.length).collect { |i| i * ins } fill = [0] * (self.length - 1) # Initialize first column values for i in 1..other.length dm[i] = [i * del, fill.flatten] end # populate matrix for i in 1..other.length for j in 1..self.length # critical comparison dm[i][j] = [ dm[i-1][j-1] + (self[j-1] == other[i-1] ? 0 : sub), dm[i][j-1] + ins, dm[i-1][j] + del ].min end end # The last value in matrix is the # Levenshtein distance between the strings dm[other.length][self.length] end |