標籤:線性篩
P.S.:100分的做法時間複雜度證明類似於調和級數。。。
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#define mod 998244353
using namespace std;
typedef long long ll;
bool f[1000050];
ll p[100050],top=0ll,ans[1000050],t[1000050],hz=0ll,l,r,k,n,zzk,tmp;
int main()
{
scanf("%lld%lld%lld",&l,&r,&k);
f[0]=f[1]=1,p[0]=0,n=floor(sqrt(r));
for (int i=2;i<=n;i++)
{
if (!f[i]) p[++top]=i;
for (int j=1;j<=top&&i*p[j]<=n;j++)
{
f[i*p[j]]=1;
if (i%p[j]==0) break;
}
}
for (ll j=l;j<=r;j++) ans[j-l]=1,t[j-l]=j;;
for (int i=1;i<=top;i++)
{
tmp=(l/p[i])*p[i];
if (tmp<l) tmp+=p[i];
for (ll j=tmp;j<=r;j+=p[i])
{
zzk=0ll;
while (t[j-l]%p[i]==0)
t[j-l]/=p[i],zzk++;
ans[j-l]=(ans[j-l]*(zzk*k+1))%mod;
}
}
for (ll j=l;j<=r;j++) if (t[j-l]!=1) ans[j-l]=(ans[j-l]*(k+1))%mod;
for (ll j=l;j<=r;j++) hz=(hz+ans[j-l])%mod;
printf("%lld",hz);
}