洛谷P1587 [NOI2016]循环之美

传送门

不会，先坑着

https://kelin.blog.luogu.org/solution-p1587

 //minamoto
 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 using namespace std;
 const int N=7e5+,E=2e6+;
 typedef int arr[N];typedef long long ll;
 struct Am{int nx,x,w;}e1[E];
 struct Ans{int nx,n,m,k;ll w;}e2[E];
 int n,m,k,M,c1,c2,K[],f1[E],f2[E];arr vis,p,mu,sum;
 int Sm(int x){
     if(x<=M) return sum[x];
     int u=(x+)%E;
     for(int i=f1[u];i;i=e1[i].nx)
     if(e1[i].x==x) return e1[i].w;
     e1[++c1]=(Am){f1[u],x,},f1[u]=c1;
     int &w=e1[c1].w,i=,j=sqrt(x);
     for(;i<=j;++i) w-=Sm(x/i);
     for(;i<=x;i=j+)
     j=x/(x/i),w-=(j-i+)*Sm(x/i);
     return w;
 }
 ll sol(int n,int m,int k){
     if(!n||!m) return ;
     int u=(2017ll*n+m+k)%E;
     for(int i=f2[u];i;i=e2[i].nx)
     if(e2[i].n==n&&e2[i].m==m&&e2[i].k==k) return e2[i].w;
     e2[++c2]=(Ans){f2[u],n,m,k,},f2[u]=c2;ll &w=e2[c2].w;
     if(k==){
         if(n>m) swap(n,m);
         int i=,j=sqrt(n),s,t=,x,y;
         for(;i<=j;++i,t=s) s=Sm(i),w+=1ll*(n/i)*(m/i)*(s-t);
         for(;i<=n;i=j+,t=s)x=n/i,y=m/i,j=min(n/x,m/y),s=Sm(j),w+=1ll*x*y*(s-t);
         u=(2017ll*m+n+k)%E;e2[++c2]=(Ans){f2[u],m,n,k,w},f2[u]=c2;
     }
     else for(int i=;i<=K[]&&K[i]<=k;++i)
     if(k%K[i]==&&mu[K[i]])
     w+=sol(m/K[i],n,K[i])*mu[K[i]];
     return w;
 }
 int main(){
 //    freopen("testdata.in","r",stdin);
     scanf("%d%d%d",&n,&m,&k);
     M=min(N-,max(k,min(n,m))),sum[]=mu[]=;
     for(int i=;i<=M;++i){
         if(!vis[i]) p[++p[]]=i,mu[i]=-;
         for(int j=,x;j<=p[]&&(x=i*p[j])<=M;++j){
             vis[x]=;
             if(i%p[j]==) break;
             mu[x]=-mu[i];
         }
         sum[i]=sum[i-]+mu[i];
     }
     for(int i=;i<=k;++i)
     if(k%i==) K[++K[]]=i;
     printf("%lld\n",sol(n,m,k));
     return ;
 }