How many prime numbers（素数）

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

 

Author

wangye

 

Source

HDU 2007-11 Programming Contest_WarmUp

#include<stdio.h>
#include<math.h>
  int prime(int x)
    {  int i;
        if(x<=2)   return 1;
        for(i=2;i<=sqrt(x*1.0);i++)   //i*i<=x  是会超时的，因为i*i每次都要计算
          {
              if(x%i==0)  
                {
                    return 0;
                    break;
                }
          }
        return 1;
    }
  int main()
    {
        int n;
        int i;
        int sum;
        int a;
        while(scanf("%d",&n)!=EOF)
          {
                 sum=0;
               for(i=0;i<n;i++)
                {
                    scanf("%d",&a);
                      if(prime(a))
                        sum++;
                }      
              printf("%d
",sum);     
          }
        return 0;
        
    }