随机函数头文件

#ifndef RANDOM_NUMBER_GENERATOR
#define RANDOM_NUMBER_GENERATOR

#include <time.h>

// used to generate random number from current seed and update seed
const unsigned long maxshort  = 65536L;
const unsigned long multiplier = 1194211693L;
const unsigned long adder = 12345L;

class RandomNumber                             
{
    private:
        // private member containing current seed
        unsigned long randSeed;
    public:
        // constructor. default 0 gives automatic seeding
        RandomNumber(unsigned long s = 0);
       
        // generate random integer 0 <= value <= n-1
        unsigned short Random(unsigned long n);
       
        // generate random real number 0 <= value < 1.0
        double fRandom(void);
};

// seed the generator
RandomNumber::RandomNumber (unsigned long s)
{
    if (s == 0)
        randSeed = time(0); // automatic seeding using system time
    else
        randSeed = s;       // user supplies the seed
}

// return random integer 0 <= value <= n-1 < 65536
unsigned short RandomNumber::Random (unsigned long n)
{
    randSeed = multiplier * randSeed + adder;
    return (unsigned short)((randSeed >> 16)  % n);
}

// return (value in range 0..65535) / 65536
double RandomNumber::fRandom (void)
{
    return Random(maxshort)/double(maxshort);
}
       
#endif  // RANDOM_NUMBER_GENERATOR