class Sample {
public:
  static int uniform(int from, int to);
  static double uniform();
  static double gaussian(double sigma);
};

static double uniform_rand(double lowerBndr, double upperBndr){
  return lowerBndr + ((double) std::rand() / (RAND_MAX + 1.0)) * (upperBndr - lowerBndr);
}

static double gauss_rand(double mean, double sigma){
  double x, y, r2;
  do {
    x = -1.0 + 2.0 * uniform_rand(0.0, 1.0);
    y = -1.0 + 2.0 * uniform_rand(0.0, 1.0);
    r2 = x * x + y * y;
  } while (r2 > 1.0 || r2 == 0.0);
  return mean + sigma * y * std::sqrt(-2.0 * log(r2) / r2);
}
//產生均勻分佈
int Sample::uniform(int from, int to){
  return static_cast<int>(uniform_rand(from, to));
}

double Sample::uniform(){
  return uniform_rand(0., 1.);
}
//產生高斯分佈
double Sample::gaussian(double sigma){
  return gauss_rand(0., sigma);
}