[ An Ac a Day ^_^ ] hdu 5894 hannnnah_j’s Biological Test lucas模板

挂零的网络赛 今天才发现是公式推错了 当时还以为是算法不够优化……

 

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>
#include<ctime>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<cstdlib>
#include<cassert>
#include<sstream>
#include<stack>
#include<list>
#include<bitset>
#define cl(a,b) memset(a,b,sizeof(a))
#define debug(x) cerr<<#x<<"=="<<(x)<<endl
using namespace std;
typedef long long ll;
typedef long double ldb;
typedef pair<int,int> pii;

const int inf=0x3f3f3f3f;
const int maxn=1<<21;
const int p=1e9+7;
const double eps=1e-8;
const double pi=acos(-1);

int dx[8]= {0,0,1,-1,1,-1,1,-1};
int dy[8]= {1,-1,0,0,-1,1,1,-1};

ll n,m,k;//p是模

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 main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        scanf("%lld%lld%lld", &n, &m, &k);
        ll res = Lucas(n - m * k - 1, m - 1);
        (res *= n) %= p;
        res *= quick_mod(m, p - 2);
        res %= p;
        printf("%lld\n", res);
    }
    return 0;
}