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
判断到sqrt(n)即可。
#include <iostream>
#include <cmath>
using namespace std;
int main(void)
{
int t;
long num[2000];
while(cin >> t)
{
int s = 0;
for(int i = 0; i < t; i++)
{
cin >> num[i];
for(long j = 2; j <= sqrt(num[i]; j++)
{
if(num[i] % j == 0)
{
s++;
break;
}
}
}
cout << t-s << endl;
}
return 0;
}
HDU-2138 How many prime numbers
原文：http://www.cnblogs.com/limyel/p/6623386.html