Module: Atig::Levenshtein::PureRuby

Defined in:
lib/atig/levenshtein.rb

Class Method Summary collapse

Class Method Details

.levenshtein(a, b) ⇒ Object 



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# File 'lib/atig/levenshtein.rb', line 12

def levenshtein(a, b)
  case
  when a.empty?
    b.length
  when b.empty?
    a.length
  else
    d = Array.new(a.length + 1) { |s|
      Array.new(b.length + 1, 0)
    }

    (0..a.length).each do |i|
      d[i][0] = i
    end

    (0..b.length).each do |j|
      d[0][j] = j
    end

    (1..a.length).each do |i|
      (1..b.length).each do |j|
        cost = (a[i - 1] == b[j - 1]) ? 0 : 1
        d[i][j] = [
                   d[i-1][j  ] + 1,
                   d[i  ][j-1] + 1,
                   d[i-1][j-1] + cost
                  ].min
      end
    end

    d[a.length][b.length]
  end
end