C + +: Random number generator (Random-number generator) detailed

Random number, C language function is rand (), C + + is a random number generator (Random-number generator) = Distribution object (distribution object) + engine (engine);

To make a function generate a different random number each time, a static (static) local variable is required so that the distribution object and the engine can hold (hold) state, each time a new one is generated;

Generates a random integer, using the Distributed object Uniform_int_distribution<>, and the default template parameter is int;

Generates a random floating-point number, uses the distributed object Uniform_real_distribution<>, and the default template parameter is double;

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Code:

#include <iostream> #include <vector> #include <string> #include <random> u  
      
Sing namespace std; Std::vector<unsigned> Good_randvec () {static std::d efault_random_engine E;//statically static std::uniform_i nt_distribution<unsigned> u (0,9);  
    Static std::vector<unsigned> ret;  
    For (size_t i=0 i<10; ++i) ret.push_back (U (e));  
return ret;  
    int main () {std::d efault_random_engine E;  
    Std::cout << "Engine:";  
    For (size_t i=0 i<10; ++i) std::cout << E () << "";  
      
    Std::cout << Std::endl;  
    Std::cout << "uniform:"; std::uniform_int_distribution<unsigned> U (0, 9);  
    That is [0, 9] for (size_t i=0 i<10; ++i) std::cout << u (e) << "";  
      
    Std::cout << Std::endl; Std::cout << "min:" << e.min () << "Max:" << E.max () <&lT  
      
    Std::endl;  
    Std::vector<unsigned> v1 (Good_randvec ());  
    Std::vector<unsigned> v2 (Good_randvec ());  
    For (size_t i=0 i<v1.size (); ++i) std::cout << v1[i] << "";  
    Std::cout << Std::endl;  
    For (size_t i=0 i<v2.size (); ++i) std::cout << v2[i] << "";  
      
    Std::cout << Std::endl;  
    Std::uniform_real_distribution<double> UD (0, 1);  
    Std::cout << "float:";  
    For (size_t i=0 i<10; ++i) std::cout << ud (e) << "";  
      
    Std::cout << Std::endl;  
return 0; }

Output:

engine:16807 282475249 1622650073 984943658 1144108930 470211272 101027544 1457850878 1458777923 2007237709 Uniform   
: 3 5 8 0 0 5 6 0 3 0 min:1 max:2147483646 0 1 7 4 5 2 0 6 6 9-3 5 8 0 0 5 6 0 3   
float:0.686773 0 .930436 0.526929 0.653919 0.701191 0.762198 0.0474645 0.328234 0.75641 0.365339

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