Torry 的困惑_牛客博客

是找前n项质数和而不是说前n项自然数的质数积
里面用了一种新的找质数的方法
https://blog.csdn.net/kevin_nan/article/details/88300966 里面有写新的质数查找方法

public class main{
    public long countPrimes(int n) {
         long sum = 1;
         int n2 = 0;
         boolean[]arr = new boolean [10000000+1];
         for(int i = 2 ;i < 10000000+1 ;i++) { 
             int j = 2;
               if(arr[i]!=true)
             while(j * i < 10000000+1 ) {
                 arr[j * i ] = true;
                 j++;
             }
         }
         for(int i = 2 ;i< 10000000+1 ;i++) {
             if(arr[i] != true) {
                 sum = (sum*i)%50000;
                 n2 ++ ;
             }
             if(n2 >= n)
                 break;
         }
                 return sum;
     }
       public static void main(String[]args) {
           Main1 m = new Main1 ();
           Scanner sc = new Scanner (System.in);
            int n = sc.nextInt();
           System.out.println(m.countPrimes(n));

       }
    }