题目
思路
杜教筛的板子,拿来练手
pace1
\[\begin{aligned}ans&=\sum_{i=1}^{n}\phi(i)\\\end{aligned}\\g(n)=1,\phi(n)=f(n)\\h(n)=\sum_{d|n}\phi(d)*g(\frac{n}{d})=n\\ \] \[h(n)=\sum_{d|n}f(d)g(\frac{n}{d})\\令F(n)=\sum_{i=1}^{n}f(i),H(n)=\sum_{i=1}^{n}h(i)\\\begin{aligned}H(n)&=\sum_{i=1}^{n}h(i)\\&=\sum_{i=1}^{n}\sum_{d|i}f(d)*g(\frac{i}{d})\\&=\sum_{i=1}^{n}\sum_{d|i}f(\frac{i}{d})g(d)\\&=\sum_{d=1}^{n}g(d)\sum_{i=1}^{\lfloor\frac{n}{d}\rfloor}f(i)\\&=\sum_{d=1}^{n}g(d)F(\lfloor\frac{n}{d}\rfloor)\\&=g(1)F(n)+\sum_{d=2}^{n}g(d)F(\lfloor\frac{n}{d}\rfloor)\end{aligned} \] \[F(n)=\frac{H(n)-\sum_{d=2}^{n}g(d)F(\lfloor\frac{n}{d}\rfloor)}{g(1)} \]其中\(H(n)\)的时间复杂度为\(O(1)\),\(g(d)\)也为\(O(1)\),对\(\sum_{d=2}^ng(d)F(\lfloor\frac{n}{d}\rfloor)\)数论分块就好了
时间复杂度\(O(n^{\frac{2}{3}})\)
pace2
\[ans=\sum_{i=1}^{n}\mu(i) \] \[设f(i)=\mu(i),g(i)=1,那么显然h(i)=(f*g)(i)=[i=1]\\设F(i)=\sum_{i=1}^nf(i),H(i)=\sum_{i=1}^{n}h(i) \] \[\begin{aligned}H(i)&=\sum_{i=1}^nh(i)\\&=\sum_{i=1}^n\sum_{d|i}f(\frac{i}{d})g(d)\\&=\sum_{d=1}^ng(d)F(\lfloor\frac{n}{d}\rfloor)\\&=g(1)F(n)+\sum_{d=2}^ng(d)F(\lfloor\frac{n}{d}\rfloor)\end{aligned} \] \[F(n)=\frac{H(i)-\sum_{d=2}^ng(d)F(\lfloor\frac{n}{d}\rfloor)}{g(1)} \]一样的,时间复杂度为$O(n^{\frac{2}{3}}) $
代码
#include<unordered_map>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
int T;
int n;
int len;
int phi[2000005],mu[2000005];
int lenp,pri[2000005];
bool vis[2000005];
long long mphi[2000005];
long long mmu[2000005];
unordered_map<int,long long> m1;
unordered_map<int,long long> m2;
void prepa(int n)
{
len=n;
mphi[1]=1;
mmu[1]=mu[1]=1;
for(int i=2;i<=n;i++)
{
if(vis[i]==0)
{
pri[++lenp]=i;
phi[i]=i-1;mu[i]=-1;
}
for(int j=1;j<=lenp&&1ll*pri[j]*i<=n;j++)
{
vis[i*pri[j]]=1;
if(i%pri[j]==0)
{
mu[i*pri[j]]=0;
phi[i*pri[j]]=pri[j]*phi[i];
break;
}
mu[i*pri[j]]=mu[i]*mu[pri[j]];
phi[i*pri[j]]=phi[i]*phi[pri[j]];
}
mmu[i]=mmu[i-1]+mu[i];
mphi[i]=mphi[i-1]+phi[i];
}
}
long long getphi(long long n)
{
if(n<=len)
return mphi[n];
if(m1.count(n))
return m1[n];
long long temp=1ll*n*(n+1)/2;
for(long long l=2,r;l<=n;l=r+1)
{
r=min(1ll*n/(n/l),1ll*n);
temp=temp-1ll*(r-l+1)*getphi(n/l);
}
return m1[n]=temp;
}
long long getmu(int n)
{
if(n<=len)
return mmu[n];
if(m2.count(n))
return m2[n];
long long temp=1;
for(long long l=2,r;l<=n;l=r+1)
{
r=min(1ll*n/(n/l),1ll*n);
temp=temp-1ll*(r-l+1)*getmu(n/l);
}
return m2[n]=temp;
}
void c_in()
{
cin>>n;
cout<<getphi(n)<<' '<<getmu(n)<<'\n';
}
int main()
{
prepa(pow((1ll<<31)-1,2.0/3));
cin>>T;
for(int i=1;i<=T;i++)
c_in();
return 0;
}