BZOJ 4407 于神之怒加强版

http://www.lydsy.com/JudgeOnline/problem.php?id=4407

题意:

给下N,M,K.求

思路:

 来自:http://blog.csdn.net/ws_yzy/article/details/50670213

#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<cstring>
#define ll long long
const ll Mod=;
ll f[],sum[],p[],s[];
bool mark[];
ll K,n,m;
ll read(){
    ll t=,f=;char ch=getchar();
    while (ch<''||''<ch){if (ch=='-') f=-;ch=getchar();}
    while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
    return t*f;
}
ll Pow(ll x,ll y){
    ll res=;
    while (y){
        if (y%) res=(res*x)%Mod;
        y/=;
        x=(x*x)%Mod;
    }
    return res;
}
void init(){
    f[]=;
    for (int i=;i<=;i++){
        if (!mark[i]){
            p[++p[]]=i;
            s[p[]]=Pow(i,K);
            f[i]=s[p[]]-;
        }
        for (int j=;j<=p[]&&p[j]*i<=;j++){
            mark[p[j]*i]=;
            if (i%p[j]==){
                f[i*p[j]]=f[i]*s[j]%Mod;
                break;
            }
            f[i*p[j]]=f[i]*f[p[j]]%Mod;
        }
    }
    for (int i=;i<=;i++)
     sum[i]=sum[i-]+f[i]%Mod;
}
int main(){
    int T=read();K=read();
    init();
    while (T--){
        n=read();m=read();
        if (n>m) std::swap(n,m);
        int j=;
        ll ans=;
        for (int i=;i<=n;i=j+){
            j=std::min(n/(n/i),m/(m/i));
            ans+=(((n/i)*(m/i)%Mod)*(sum[j]-sum[i-]))%Mod;
            ans%=Mod;
        }
        printf("%lld\n",ans);
    }
    return ;
}