学步园

 1public static ArrayList GeneratePrimes(int ubound)

 2        {

 3            BitArray flags = new BitArray(ubound + 1, true);

 4            for(int i = 2; i <= (int)Math.Sqrt(ubound); i++)

 5            {

 6                if(flags[i])

 7                {

 8                    for(int j = i; j * i <= ubound; j++)

 9                    {

10                        flags[i * j] = false;

11                    }

12                }

13            }

14
15            ArrayList primes = new ArrayList();

16            for(int i = 2; i <= ubound; i++)

17            {

18                if(flags[i])

19                    primes.Add(i);

20            }

21            return primes;

22        }