Defined in header <random>  

template< class IntType = int > class discrete_distribution;  (since C++11) 
std::discrete_distribution
produces random integers on the interval [0, n)
, where the probability of each individual integer i
is defined as w
i/S, that is the weight of the i
th integer divided by the sum of all n
weights.
std::discrete_distribution
satisfies all requirements of RandomNumberDistribution.
IntType    The result type generated by the generator. The effect is undefined if this is not one of short , int , long , long long , unsigned short , unsigned int , unsigned long , or unsigned long long . 
Member type  Definition 

result_type  IntType 
param_type (C++11)  the type of the parameter set, see RandomNumberDistribution. 
(C++11)  constructs new distribution (public member function) 
(C++11)  resets the internal state of the distribution (public member function) 
Generation 

(C++11)  generates the next random number in the distribution (public member function) 
Characteristics 

obtains the list of probabilities (public member function) 

(C++11)  gets or sets the distribution parameter object (public member function) 
(C++11)  returns the minimum potentially generated value (public member function) 
(C++11)  returns the maximum potentially generated value (public member function) 
(C++11)(C++11)(removed in C++20)  compares two distribution objects (function) 
(C++11)  performs stream input and output on pseudorandom number distribution (function template) 
#include <iostream> #include <iomanip> #include <map> #include <random> int main() { std::random_device rd; std::mt19937 gen(rd()); std::discrete_distribution<> d({40, 10, 10, 40}); std::map<int, int> map; for(int n=0; n<10000; ++n) { ++map[d(gen)]; } for(const auto& [num, count] : map) { std::cout << num << " generated " << std::setw(4) << count << " times\n"; } }
Possible output:
0 generated 4037 times 1 generated 962 times 2 generated 1030 times 3 generated 3971 times
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