poj 3292 Semiprime Hnumbers 夜

http://poj.org/problem?id=3292

#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>

using namespace std;

const int N=1000001;
int ans[N];
void findans()
{
    memset(ans,0,sizeof(ans));
    for(int i=5;i<N;i+=4)
    {
        for(int j=5;j<N;j+=4)
        {
            int temp=i*j;
            if(temp>=N)
            break;
            if(ans[i]==0&&ans[j]==0)
            {
                ans[temp]=1;
            }
            else
            {
                ans[temp]=-1;
            }
        }
    }
    int sum=0;
    for(int i=1;i<N;++i)
    {
        if(ans[i]==1)
        ++sum;
        ans[i]=sum;
    }
}
int main()
{
    findans();
    int n;
    while(cin>>n)
    {
        if(n==0)
        break;
        cout<<n<<" "<<ans[n]<<endl;
    }
    return 0;
}