求素數(質數)的算法

class Program
    {
        static void Main(string[] args)
        {
            for (int i = 2; i <= 100; i++)
            {
                bool flag = true;
                int k =  Convert.ToInt32(Math.Sqrt(i));
                for (int j = 2; j <= k; j++)
                {
                    if (i % j == 0)
                    {
                        flag = false;                    
                        break;
                    }
                }
                if (flag == true)
                {
                    Console.WriteLine(i);
                }
            }
            Console.ReadLine();
        }
    }