洛谷 P2714 四元组统计

错误记录：42行N写成n；事实上除了读入以外，此题的小n没有任何用途

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<vector>
 using namespace std;
 #define fi first
 #define se second
 #define mp make_pair
 #define pb push_back
 typedef long long ll;
 typedef unsigned long long ull;
 typedef pair<int,int> pii;
 const ll N=;
 ll b[],ans;
 ll mu[],prime[],len,n;
 bool nprime[];
 ll F(ll x)
 {
     ll i,ans=;
     for(i=x;i<=N;i+=x)    ans+=b[i];
     return __int128(ans)*(ans-)*(ans-)*(ans-)/;
 }
 int main()
 {
     ll i,j,t;
     mu[]=;
     for(i=;i<=N;i++)
     {
         if(!nprime[i])    prime[++len]=i,mu[i]=-;
         for(j=;j<=len&&i*prime[j]<=N;j++)
         {
             nprime[i*prime[j]]=;
             if(i%prime[j]==)    {mu[i*prime[j]]=;break;}
             else    mu[i*prime[j]]=-mu[i];
         }
     }
     while(scanf("%lld",&n)==)
     {
         memset(b,,sizeof(b));
         for(i=;i<=n;i++)    scanf("%lld",&t),b[t]++;
         ans=;
         for(i=;i<=N;i++)
         {
             ans+=mu[i]*F(i);
         }
         printf("%lld\n",ans);
     }
     return ;
 }