How many prime numbers

Problem Description

  Give you a lot of positive integers, just to find out how many prime numbers there are.

Input

  There are a lot of cases. In each case, there is an integer N representing the number of integers to find. Each integer won’t exceed 32-bit signed integer, and each of them won’t be less than 2.

Output

  For each case, print the number of prime numbers you have found out.

Sample Input

3

2 3 4

Sample Output

2

 

1、题意:输入n个整数，输出其中有几个素数。
2、思路:因为数很多，所以用scanf输入。
3、代码:

 

#include<stdio.h>#include<math.h>int main(){int flag,i,a,x,n;while(scanf("%d",&n)!=EOF){x=0;while(n--){scanf("%d",&a);flag=0;for(i=2;i<=sqrt(1.0*a);i++){if(a%i==0){flag=1;break;}}if(flag==0)x++;}printf("%d\n",x);}return 0;}

4、总结:求素数，只需要暴力到n的二分之一次方即可。