HDU 2138 How many prime numbers

How many prime numbers

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 16170    Accepted Submission(s): 5578

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

 

这道题=.=

很好很水很神奇。

他说在32位以内，数太大了打表肯定不行。然后这题可以直接判定素数暴力过……

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