"C + +" random number engine

RAND ()

• Basic: When using random numbers, it is often seen that the C standard library provides the function rand (), which generates an integer number between 0 and Rand_max ;
• Distribution: in order to obtain a random number within a given range, the resulting random number is usually taken out:rand ()%n,rand ()% (n-m) +m;
• seed: by Srand () sets the random number seed, the seed does not change the case, each time the program runs, calls Rand (), will generate the same sequence of random numbers ;
• floating point: use double (rand ())/Rand_max to generate a random floating-point number in the range of 0-1, but the accuracy can be problematic;
• In general, the Srand () seed can be set using time ( 0) and Time () takes the seconds of the system, so if Srand () and rand () call intervals of less than 1s, the same random number is generated, such as:
  

       for 0 ten; i++)    {        Srand (time (0));         << rand () << Endl;    }

C++11:default_random_engine

• Basic: C++11 provides a new random number generator, a random number engine default_random_engine, which contains header files when used #include <random>;
• scope: By default, the build scope of the default_random_engine is a unsigned, which can be obtained from the method min () and Max () .
• seed: similar to rand (), Default_random_engine also needs to change the resulting sequence by a random number seed, which can be set by invoking the method seed ();
• distribution and floating point: the random number engine can set the build range by distributing objects,uniform_int_distribution<unsigned> or Uniform_real_distribution <double>;
• relative rand (), you can use uniform_real_distribution<> to generate random floating-point numbers, and without worrying about the accuracy problem, the random number engine is used as follows:
  

  Default_random_engine e;//defining the random number engineUniform_int_distribution<unsigned> ID (1,Ten);//Integral type distributionuniform_real_distribution<Double> dd (0,1.0);//floating-point distributionE.seed (Ten);//set random number seed     for(size_t i =0; I <Ten; i++) {cout<< ID (E) <<" ; "<< DD (e) <<Endl; }

"C + +" random number engine