levDis.swift

func levDis(w1: String, w2: String) -> Int {
 
  let (t, s) = (w1.characters, w2.characters)
 
  let empty = Repeat(count: s.count, repeatedValue: 0)
  var mat = [[Int](0...s.count)] + (1...t.count).map{[$0.0] + empty}
 
  for (i, tLett) in t.enumerate() {
    for (j, sLett) in s.enumerate() {
      mat[i + 1][j + 1] = tLett == sLett ?
        mat[i][j] : min(mat[i][j], mat[i][j + 1], mat[i + 1][j]).successor()
    }
  }
  return mat.last!.last!
}

func levDis(w1: String, w2: String) -> Int {
 
  let (t, s) = (w1.characters, w2.characters)
 
  let empty = Repeat(count: s.count, repeatedValue: 0)
  var last = [Int](0...s.count)
 
  for (i, tLett) in t.enumerate() {
    var cur = [i + 1] + empty
    for (j, sLett) in s.enumerate() {
      cur[j + 1] = tLett == sLett ? last[j] : min(last[j], last[j + 1], cur[j]).successor()
    }
    last = cur
  }
  return last.last!
}