code: public static double quadraticEuclidean(double[] v1, double[] v2) {
      final double d1 = v1[0] - v2[0], d2 = v1[1] - v2[1];
      return (d1 * d1) + (d2 * d2);
    }
docs: Squared euclidean distance. 2d.
  
  @param v1 First double[]
  @param v2 Second double[]
  @return Quadratic distance