ACM数论模版

#include<bits/stdc++.h>
using namespace std;
const int MAXN= 100005;
const int mod = 1e9+7;
typedef long long LL;
LL c[1005][1005];
LL mu[MAXN];
LL euler[MAXN];
int mu[MAXN];
void Mubius()//莫比乌斯函数
{
    mu[1]=1;
    for(int i=1;i<MAXN;++i)
    {
        for(int j=i+i;j<MAXN;j+=i)
        {
            mu[j]-=mu[i];
        }
    }
}
void extend_gcd(int a, int b, int &x, int &y)//扩展欧几里得
{
    if(x==0)
    {
        a=1;
        b=0;
        return ;
    }
    extend_gcd(b, a%b, x, y);
    int t=x;
    x=y;
    y=t-a/b*y;
    return ;
}
void comb()//组合数表
{
    c[0][0]=1;
    for(int i=1; i<1000; ++i)
    {
        c[i][0]=1;
        for(int j=1; j<=i; ++j)
        {
            c[i][j]=(c[i-1][j]+c[i-1][j-1])%mod;
        }
    }
    return ;
}
void euler_t()//直接求欧拉函数值
{
    euler[1]=1;
    for(int i=2; i<MAXN; ++i)
        euler[i]=i;
    for(int i=2; i<MAXN; ++i)
    {
        if(euler[i]==i)
            for(int j=i; j<MAXN; j+=i)
            {
                euler[j]=euler[j]/i*(i-1);
            }
    }
}
LL quick_pow(LL a, LL b)//快速幂
{
    LL res=1;
    while(b)
    {
        if(b&1)
            res=res*a%mod;
        a=a*a%mod;
        b>>=1;
    }
    return res;
}
LL Comb(LL a,LL b, LL p)//求组合数
{
    if(a < b) return 0;
    if(a == b) return 1;
    if(b > a-b) b = a-b;
    LL ans = 1, ca = 1, cb = 1;
    for(LL i=0; i<b; ++i)
    {
        ca = (ca*(a-i))%p;
        cb = (cb*(b-i))%p;
    }
    ans = (ca*quick_pow(cb, mod-2))%mod;
    return ans;
}
LL Lucas(int n, int m, int p)
{
    LL ans = 1;
    while(n && m && ans)
    {
        ans = (ans * Comb(n%mod, m%mod, mod))%mod;
        n /= mod;
        m /= mod;
    }
    return ans;
}
 /*
LL quick_mod(LL a, LL b)  
{  
    LL ans = 1;  
    a %= p;  
    while(b)  
    {  
        if(b & 1)  
        {  
            ans = ans * a % p;  
            b--;  
        }  
        b >>= 1;  
        a = a * a % p;  
    }  
    return ans;  
}  

LL C(LL n, LL m)  
{  
    if(m > n) return 0;  
    LL ans = 1;  
    for(int i=1; i<=m; i++)  
    {  
        LL a = (n + i - m) % p;  
        LL b = i % p;  
        ans = ans * (a * quick_mod(b, p-2) % p) % p;  
    }  
    return ans;  
}  

LL Lucas(LL n, LL m)  
{  
    if(m == 0) return 1;  
    return C(n % p, m % p) * Lucas(n / p, m / p) % p;  
}  
*/
int get_euler(int n)//欧拉函数表
{
    int ans=n;
    for(int i=2; i*i<=n; ++i)
    {
        if(n%i==0)
        {
            ans=ans/i*(i-1);
            while(n%i==0)
                n/=i;
        }
    }
    if(n!=1)
        ans=ans/n*(n-1);
    return ans;
}
int main()
{
    comb();
    euler_t();
    LL a, b;
    while(~scanf("%lld %lld", &a, &b))
    {
        printf("%lld\n", Lucas(a, b, mod));
    }
    return 0;
}