c/c++产生随机数

c库伪随机数发生器

rand 

srand

大多时候用时间产生随机发生器的seed

int GetRandomNum(int min, int max,int seed)
{

//srand((unsigned)time(NULL)); //生成seed
srand(seed);
return( rand() % (max - min) + min);
}

c++11 引入的伪随机数发生器.随机数抽象成随机数引擎和分布两部分.引擎用来产生随机数,分布产生特定分布的随机数

常用的就是线性均匀分布

uniform_int_distribution 

uniform_real_distribution

std::random_device rd;//来产生一个随机数当作种子
std::uniform_int_distribution<int> uni_dist(0, 9999999); //指定范围的随机数发生器
std::cout << uni_dist(rd) << std::endl;

还有一些其他发生器，如 伯努里分布、泊松分布、正态分布 

// ConsoleApplication4.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <random>
#include <memory>
#include <iostream>

using namespace std;

class Random {
public:
const static  unsigned int  maxRand = std::random_device::max();
static Random& getInstance()
{
static Random instance;
return instance;
}
unsigned int  getInteger() noexcept {
return (*dist)(rd);
}
unsigned int  GetMTEngineInteger() noexcept {
return (*mtEngine)();
}
uint64_t  GetMTEngine64Integer() noexcept {
return (*mtEngine64)();
}

unsigned int  GetRand0Integer() noexcept {
return (*rand0Engine)();
}

auto GetRanlux48Integer() noexcept ->decltype(auto) {
return (*ranlux48Engine)();
}

private:
Random() noexcept {
mtEngine = std::make_shared<std::mt19937>(rd());
mtEngine64 = std::make_shared<std::mt19937_64>(rd());
dist = std::make_shared<std::uniform_int_distribution< unsigned int >>(std::uniform_int_distribution< unsigned int >(0, maxRand));
rand0Engine = make_shared<std::minstd_rand0>(rd());
ranlux48Engine = make_shared<std::ranlux48>(rd());
}
std::random_device rd;
std::shared_ptr<std::mt19937> mtEngine;		//32-bit Mersenne Twister by Matsumoto and Nishimura, 1998
std::shared_ptr<std::mt19937_64> mtEngine64; //64-bit Mersenne Twister by Matsumoto and Nishimura, 2000(马特赛特旋转演算法)
std::shared_ptr<std::minstd_rand0> rand0Engine;
std::shared_ptr<std::ranlux48> ranlux48Engine;

std::shared_ptr<std::uniform_int_distribution< unsigned int > > dist;
};

int main()
{

cout << Random::getInstance().GetMTEngineInteger() << endl;
cout << Random::getInstance().GetMTEngine64Integer() << endl;
cout << Random::getInstance().GetRand0Integer() << endl;
cout << Random::getInstance().GetRanlux48Integer() << endl;

cout << Random::getInstance().getInteger() << endl;

return 0;
}