CF 576A 猜数

A给出一个数x，B每次猜一个y，A回答B，x是否可以被y整除，求出要猜的最小次数和需要猜的数。

枚举每个素数p，可以知道如果p^k<=n，则p^k一定需要选

Sample test(s)
input
4
output
3
2 4 3
input
6
output
4
2 4 3 5

# include <iostream>
# include <cstdio>
# include <cstring>
# include <algorithm>
# include <string>
# include <cmath>
# include <queue>
# include <list>
# define LL long long
using namespace std ;

int ans[1010] ;

bool isp (int val )
{
     int i ;
     if (val == 1)
       return 0 ;
     for (i = 2 ; i*i <= val ; i++)
     {
         if (val % i == 0)
             return 0 ;
     }
     return 1 ;

}

int main()
{
    //freopen("in.txt","r",stdin) ;
    int n ;
    while(scanf("%d",&n ) != EOF)
    {
        int i ;
        int l = 0 ;
        if (n == 1)
        {
            printf("0
") ;
            continue ;
        }

        for (i = 2 ; i <= n ; i++)
        {
            if (isp(i) == 0)
                continue ;
            int p = i ;
            while(p <= n)
            {
                ans[l] = p ;
                l++ ;
                p *= i ;
            }
        }
        printf("%d
" , l) ;
        for (i = 0 ; i < l-1 ; i++)
            printf("%d " , ans[i]) ;
        printf("%d
" , ans[i]) ;
    }



    return 0;
}