FZU 2238 Daxia & Wzc's problem

公式。

$a×C_{m + i - 1}^m + d×C_{m + i - 1}^{m + 1}$。

推导过程可以看http://blog.csdn.net/queuelovestack/article/details/52260127

#pragma comment(linker, "/STACK:1024000000,1024000000")

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

#include<vector>

#include<map>

#include<set>

#include<queue>

#include<stack>

#include<iostream>

using namespace std;

typedef long long LL;

const double pi=acos(-1.0),eps=1e-;

void File()

{

    freopen("D:\\in.txt","r",stdin);

    freopen("D:\\out.txt","w",stdout);

}

template <class T>

inline void read(T &x)

{

    char c = getchar(); x = ;while(!isdigit(c)) c = getchar();

    while(isdigit(c)) { x = x *  + c - ''; c = getchar();  }

}

LL a,d,i,m,p;

LL quick_mod(LL a, LL b)

{

    LL ans = ;

    a %= p;

    while(b)

    {

        if(b & )

        {

            ans = ans * a % p;

            b--;

        }

        b >>= ;

        a = a * a % p;

    }

    return ans;

}

LL C(LL n, LL m)

{

    if(m > n) return ;

    LL ans = ;

    for(int i=; i<=m; i++)

    {

        LL a = (n + i - m) % p;

        LL b = i % p;

        ans = ans * (a * quick_mod(b, p-) % p) % p;

    }

    return ans;

}

LL Lucas(LL n, LL m)

{

    if(m == ) return ;

    return C(n % p, m % p) * Lucas(n / p, m / p) % p;

}

int main()

{

    while(~scanf("%I64d%I64d%I64d%I64d", &a,&d,&m, &i))

    {

        p=;

        printf("%I64d\n", (a*Lucas(m+i-,m)+d*Lucas(m+i-,m+))%p);

    }

    return ;

}