C++ STL 随机数用法介绍

目录

一：C语言中的随机数

二：C++中的随机数

    1. 生成随机数的例子

    2. 随机数引擎

    3. 随机数引擎适配器

    4. C++中预定义的随机数引擎，引擎适配器

    5. 随机数分布

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一：C语言中的随机数

<stdlib.h>//初始化随机种子
srand(static_cast<unsigned int>(time(nullptr)));//生成随机数
cout << rand() << endl;//生成一个区间的内随机数(min, max)
return static_cast<int>(rand() % (max + 1UL - min)) + min;//生成100内随机数
int num = rand() % 100；//生成1-100内随机数
int num = rand() % 100 + 1;

二：C++中的随机数

    1. 生成随机数的例子

include <random>
#include <map>
#include <iostream>int main()
{static const int NUM = 1000000;//第一步 产生随机种子std::random_device seed;//第二步：使用随机数引擎生成器std::mt19937 gen(seed());//第三步：为随机数选择一种分布，此处选择均匀分布std::uniform_int_distribution<> uniformDist(0, 20); // min= 0; max= 20for (int i = 1; i <= NUM; ++i) {std::cout << uniformDist(gen) << " ";}
}

    2. 随机数引擎

引擎	说明
random_device	真随机数(非基于软件生成器)，通常用来产生随机种子
linear_congruential_engine	线性同余法生成器
mersenne_twister_engine	梅森素数法生成器
subtract_with_carry_engine	带进位减法随机数生成器

    3. 随机数引擎适配器

template<class Engine, size_t p, size_t r> class discard_block_engine {...}
template<class Engine, size_t w, class UIntT> class independent_bits_engine {...}
template<class Engine, size_t k> class shuffle_order_engine {...}

    4. C++中预定义的随机数引擎，引擎适配器

  5. 随机数分布

template<class IntType = int> class uniform_int_distribution
uniform_int_distribution(IntType a = 0, IntType b = numeric_limits<IntType>::max());template<class RealType = double> class uniform_real_distribution
uniform_real_distribution(RealType a = 0.0, RealType b = 1.0);class bernoulli_distribution
bernoulli_distribution(double p = 0.5);template<class IntType = int> class binomial_distribution
binomial_distribution(IntType t = 1, double p = 0.5);template<class IntType = int> class geometric_distribution
geometric_distribution(double p = 0.5);template<class IntType = int> class negative_binomial_distribution
negative_binomial_distribution(IntType k = 1, double p = 0.5)template<class IntType = int> class poisson_distribution
poisson_distribution(double mean = 1.0);template<class RealType = double> class exponential_distribution
exponential_distribution(RealType lambda = 1.0);template<class RealType = double> class gamma_distribution
gamma_distribution(RealType alpha = 1.0, RealType beta = 1.0);template<class RealType = double> class weibull_distribution
weibull_distribution(RealType a = 1.0, RealType b = 1.0);template<class RealType = double> class extreme_value_distribution
extreme_value_distribution(RealType a = 0.0, RealType b = 1.0);template<class RealType = double> class normal_distribution
normal_distribution(RealType mean = 0.0, RealType stddev = 1.0);template<class RealType = double> class lognormal_distribution
lognormal_distribution(RealType m = 0.0, RealType s = 1.0);template<class RealType = double> class chi_squared_distribution
chi_squared_distribution(RealType n = 1);template<class RealType = double> class cauchy_distribution
cauchy_distribution(RealType a = 0.0, RealType b = 1.0);template<class RealType = double> class fisher_f_distribution
fisher_f_distribution(RealType m = 1, RealType n = 1);template<class RealType = double> class student_t_distribution
student_t_distribution(RealType n = 1);template<class IntType = int> class discrete_distribution
discrete_distribution(initializer_list<double> wl);template<class RealType = double> class piecewise_constant_distribution
template<class UnaryOperation>piecewise_constant_distribution(initializer_list<RealType> bl,
UnaryOperation fw);template<class RealType = double> class piecewise_linear_distribution
template<class UnaryOperation>piecewise_linear_distribution(initializer_list<RealType> bl,
UnaryOperation fw);