Hdu 1286 找新朋友

类似筛选法，注意是新朋友，不是老朋友。

#include <iostream>#include <cstdlib>#include <cstdio>#include <cstring>#include <string>#include <algorithm>using namespace std;const int MAXN = 32769;int n, tot;bool vis[MAXN];int S[MAXN];void init(){    tot = 0;    memset(vis, 0, sizeof(vis));}void read_case(){    init();    scanf("%d", &n);    for(int i = 2; i < n; i++) if(!vis[i])    {        if(n % i == 0)        {            for(int j = i; j < n; j += i) vis[j] = 1;        }    }}void solve(){    int ans = 0;    read_case();    for(int i = 1; i < n; i++) if(!vis[i]) ans++;    printf("%d\n", ans);}int main(){    int T;    scanf("%d", &T);    while(T--)    {        solve();    }    return 0;}