//在【ａ，ｂ】區(qū)間均勻分布的隨機數(shù)
double myu(double a, double b) 
{
  double y;                    
  if(a>b) 
  {
	printf("\nThe first parameter should be less than the second!");
	exit(1);
  }
  y = (double)rand()/(RAND_MAX);
  return (a+(b-a)*y); 
}

// 指數(shù)分布  

// 指數(shù)分布的密度函數(shù)是 f(x) = Lambda*exp(-Lambda*X)
// 概率分布函數(shù)：F(X) = 1 - exp(-Lambda*X)
// U=F(X) = 1 - exp(-Lambda*X)
// 所以 X=（-1/Lambda）*Log(U)

double myexp(double beta)  // 此處的beta=1/Lambda
{                          
  double u;
  
do
 {
    // 【0，1】區(qū)間均勻分布  
     u = myu(0,1);  
  }  while(u<=0||u>=1);
  return (-1*beta*log(u));
}


// 正泰分布 myn(均值，方差)
double myn(double mu, double sigma2) // Normal Distribution
{                                    
  double mu1, mu2, z;
  do 
  {
    mu1 = myu(0,1);
    mu2 = myu(0,1);
  } while (mu1<=0||mu1>=1);
  z = sqrt(-2*log(mu1))*sin(2*3.14159*mu2); 
                                        // Z是服從myn(0,1)標(biāo)準(zhǔn)正態(tài)分布的隨機數(shù)
  return (mu+sqrt(sigma2)*z);
}