hdu Largest prime factor

#include <cstdio>#include <cstring>#include <algorithm>#define maxn 1000100using namespace std;int f[maxn];void inti(){    int num=0;    for(int i=2; i<maxn; i++)    {        if(f[i]==0)        {            num++;            for(int j=i; j<maxn; j+=i)            {                f[j]=num;            }        }    }}int main(){    int n;    inti();    while(scanf("%d",&n)!=EOF)    {        printf("%d\n",f[n]);    }    return 0;}