[杜教筛模板] 51Nod 1244 莫比乌斯函数之和

模板题

#include
#include
#include
#include 
typedef long long ll;
using namespace std;
using namespace std::tr1;


const int maxn=10000000;

int prime[1000000],num;
int vst[maxn+5],miu[maxn+5];

inline void Pre(){
  miu[1]=1;
  for (int i=2;i<=maxn;i++){
    if (!vst[i]) prime[++num]=i,miu[i]=-1;
    for (int j=1;j<=num && (ll)i*prime[j]<=maxn;j++){
      vst[i*prime[j]]=1;
      if (i%prime[j]==0){
	miu[i*prime[j]]=0;
	break;
      }
      miu[i*prime[j]]=miu[i]*miu[prime[j]];
    }
  }
  for (int i=1;i<=maxn;i++) miu[i]+=miu[i-1];
}

unordered_map S;

inline int Sum(ll n){
  if (n<=maxn) return miu[n];
  if (S.find(n)!=S.end()) return S[n];
  int tem=1; ll l,r;
  for (l=2;l*l<=n;l++) tem-=Sum(n/l);
  for (ll t=n/l;l<=n;l=r+1,t--){
    r=n/t;
    tem-=(r-l+1)*Sum(t);
  }
  return S[n]=tem;
}

int main(){
  ll l,r;
  freopen("t.in","r",stdin);
  freopen("t.out","w",stdout);
  Pre();
  scanf("%lld%lld",&l,&r); swap(l,r); swap(l,r);
  printf("%d\n",Sum(r)-Sum(l-1));
  return 0;
}