题目1047：素数判定----------------------一定不要忘了对负数，0,1的判断

AC:

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    int n;
    while(cin>>n)
    {
        if (n<2) cout<<"no"<<endl;
        else 
        { 
        int k=(int)sqrt(n*1.0);
        int i=0;
        for (i=2;i<=k;i++)
          if (n%i==0) break;
        if (i>k) cout<<"yes"<<endl;
        else cout<<"no"<<endl;
        }
    }
    return 0;
}