[bzoj4407]于神之怒加强版

http://blog.csdn.net/w_yqts/article/details/78970490
Orz w_yqts

#include 
using namespace std;
#define ll long long
#define p 1000000007
#define N 5000005
inline int read()
{
    char ch=getchar();
    int x=0;
    while ('0'>ch || ch>'9') ch=getchar();
    while ('0'<=ch && ch<='9') x=(x<<3)+(x<<1)+ch-'0',ch=getchar();
    return x;
}
inline int power(int x,int m)
{
    ll s1=1LL,s2=(ll)x;
    while (m)
    {
        if (m&1) s1=s1*s2%p;
        m>>=1;
        s2=s2*s2%p;
    }
    return s1;
}
int pn,g[N],pr[N],flag[N],mi[N],k;
inline void solve()
{
    ll ans=0LL;
    int n=read(),m=read();
    if (n>m) swap(n,m);
    for (int i=1,pos;i<=n;i=pos+1)
    {
        pos=min(n/(n/i),m/(m/i));
        ans=(ans+(ll)(n/i)*(m/i)%p*(g[pos]-g[i-1]))%p;
    }
    printf("%d\n",(ans+p)%p);
}
int main()
{
    int T;
    T=read(),k=read();
    flag[1]=1;g[1]=1;
    for (int i=2;i<=5000000;++i)
    {
        if (!flag[i])
        {
            pr[++pn]=i;
            mi[pn]=power(i,k);
            g[i]=mi[pn]-1;
        }
        for (int j=1;j<=pn && pr[j]*i<=5000000;++j)
        {
            flag[i*pr[j]]=1;
            if (i%pr[j]==0)
            {
                g[i*pr[j]]=(ll)(g[i])*mi[j]%p;
                break;
            }
            g[i*pr[j]]=(ll)(g[i])*g[pr[j]]%p;
        }
    }
    for (int i=2;i<=5000000;++i) g[i]=(g[i]+g[i-1])%p;
    while (T--) solve();
}