欧拉计划 第7题

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.

What is the 10 001st prime number?

 

class Program

    {

        private static List<long> primes = new List<long>(10000000);



        static void Main(string[] args)

        {

            primes.Add(2);

            for (int i = 0; primes.Count < 10001; i++)

            {

                NextPrime();

            }

            Console.WriteLine(primes.Last());

        }



        private static long NextPrime()

        {

            long last = primes.Last();

            long n = last + 1;

            while (true)

            {

                foreach (var item in primes)

                {

                    if (n % item == 0)

                    {

                        goto LoopOut;

                    }

                }

                primes.Add(n);

                return n;



            LoopOut:

                n++;

            }

        }

    }