C++11 生成正态分布随机数

要生成服从标准正态分布的随机数，类似matlab中的randn函数。
C++11中引入了正态分布模板类std::normal_distribution，在头文件<random>中。

• 每次运行程序生成相同的随机序列

#include <iostream>
#include <random>
using namespace std;

int main()
{
  std::default_random_engine gen;
  //int seed = 3; 也可以设置一个种子
  //std::default_random_engine gen(seed);
  std::normal_distribution<double> dis(0,1);

  std::cout << "some normal random numbers: \n";
  for (int i=0; i<5; ++i)
      std::cout << dis(gen) << " ";
  std::cout<<endl;
  for (int i=0; i<5; ++i)
      std::cout << dis(gen) << " ";
  std::cout << endl;

  return 0;
}

• 每次运行程序产生不同的随机序列

#include <iostream>
#include <random>
#include <chrono>
using namespace std;

int main()
{
  // construct a random generator engine from a time-based seed
  unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
  std::default_random_engine gen(seed);
  std::normal_distribution<double> dis(0,1);

  std::cout << "some normal random numbers: \n";
  for (int i=0; i<5; ++i)
      std::cout << dis(gen) << " ";
  std::cout<<endl;

  return 0;
}

参考：https://blog.csdn.net/fengbingchun/article/details/73770856