static int levenWithSwapsIC(S s, S t) {
  // degenerate cases
  if (s.equals(t)) return 0;
  int ls = s.length(), lt = t.length();
  if (ls == 0) return lt;
  if (lt == 0) return ls;

  int[] vx = new int[lt + 1];
  int[] v0 = new int[lt + 1];
  int[] v1 = new int[lt + 1];

  for (int i = 0; i < v0.length; i++) v0[i] = i;

  for (int i = 0; i < ls; i++) {
      v1[0] = i + 1;

      for (int j = 0; j < lt; j++) {
          int cost = equalsIgnoreCase(s.charAt(i), t.charAt(j)) ? 0 : 1;
          int d = min3(
            v1[j] + 1,     // delete
            v0[j + 1] + 1, // insert
            v0[j] + cost); // edit
            
          if (i > 0 && j > 0 && equalsIgnoreCase(s.charAt(i), t.charAt(j-1)) && equalsIgnoreCase(s.charAt(i-1), t.charAt(j)))
            d = min(d, vx[j-1] + 1); // transposition
          v1[j + 1] = d;
      }

      // rotate arrays
      int[] v = vx;
      vx = v0;
      v0 = v1;
      v1 = v;
  }

  return v0[lt];
}