random.h

这是本人精心搜集的关于常用图论算法的一套源码

#include <math.h>
#define max_int 32767
class Random 
{
  public:
   Random(bool pseudo=true);
    // Declare random-number generation methods here.
   double random_real( );
   int random_integer(int low, int high);
   int poisson(double mean);
  private:
    int reseed( ); //Re-randomize theseed .
   int seed,multiplier, add_on; // constants for use in arithmetic operations
};
Random::Random(bool pseudo)
// Post: The values ofseed ,add on , andmultiplier are initialized. Theseed
// is initialized randomly only ifpseudo == false. 
{
  if(pseudo)seed=1;
   else seed=time(NULL)% max_int;
  multiplier = 2743;
  add_on = 5923;
}
int Random::reseed( )
// Post: Theseed is replaced by a psuedorandom successor. 
{ seed=seed*multiplier+add_on;
  return seed;
}
double Random::random_real( )
/* Post: A random real_number between 0 and 1 is returned. */
{
  double max = max_int+1.0;
  double temp = reseed( );
  if (temp<0) temp=temp+max;
  return temp/max;
}
int Random::random_integer(int low, int high)
/* Post: A random integer betweenlow andhigh (inclusive) is returned. */
{
 if(low>high) return random_integer(high,low);
  else return ((int) ((high-low+1)*random_real( )))+low;
}  
int Random::poisson(double mean)
/* Post: A random integer, reecting a Poisson distribution with parametermean ,
is returned. */
{
 double limit = exp(-mean);
 double product=random_real( );
 int count = 0;
 while(product>limit)
  { count++;
    product *= random_real( );
  }
 return count;
}