C++ 数论相关题目 求组合数III

#include 
#include 

typedef long long LL;
using namespace std;

int p;

int qmi(int a, int k)
{
    int res = 1;
    while(k)
    {
        if(k & 1)
        {
            res = (LL)res * a % p;
        }
        a = (LL)a * a % p;
        k >>= 1;
    }
    return res;
}

int C(int a, int b)
{
    int res = 1;
    for(int i = 1, j = a; i <= b; i ++ , j -- )
    {
        res = (LL)res * j % p;
        res = (LL)res * qmi(i, p - 2) % p;
    }
    return res;
}

int lucas(LL a, LL b)
{
    if(a < p && b < p) //如果比较小，就用普通方法
        return C(a, b); 
    return (LL)C(a % p, b % p) * lucas(a / p, b / p) % p; //大数用lucas定理
}

int main ()
{
    int n;
    cin >> n;
    while(n -- )
    {
        LL a, b;
        cin >> a >> b >> p;
        cout << lucas(a, b) << endl;
    }
    
    return 0;
}