c++產生隨機數的方法

c庫偽隨機數發生器

rand 

srand

大多時候用時間產生隨機發生器的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 引入的偽隨機數發生器.隨機數抽象成隨機數引擎和分布兩部分.引擎用來產生隨機數,分布產生特定分布的隨機數

常用的就是線性均勻分布

uniform_int_distribution 

uniform_real_distribution

std::random_device rd;//來產生一個隨機數當作種子

std::uniform_int_distribution<int> uni_dist(0, 9999999); //指定范圍的隨機數發生器

std::cout << uni_dist(rd) << std::endl;

還有一些其他發生器，如 伯努里分布、泊松分布、正態分布 

// ConsoleApplication4.cpp : 定義控制臺應用程序的入口點。

//

#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(馬特賽特旋轉演算法)

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;

}