light oj 1095 组合数学

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <iostream>
#include <algorithm>
#include <climits>
#include <queue>
#define ll long long

using namespace std;


const int MAX = 200005;
const ll MOD = 1e9+7;
ll F[1010],C[1010][1010];

void init()
{
    F[0] = 1;
    F[1] = 0;
    F[2] = 1;
    for(int i = 3; i <= 1000; i++)
        F[i] = (i-1)*(F[i-1]+F[i-2])%MOD;

    for(int i = 0; i <= 1000; i++)
    {
        for(int j = 0; j <= i; j++)
        {
            if(j == 0)
                C[i][j] = 1;
            else
                C[i][j] = (C[i-1][j]+C[i-1][j-1])%MOD;
        }
    }
}

void solve()
{
    int n,m,k;
    scanf("%d %d %d",&n,&m,&k);
    ll ans = 0;
    for(int i = 0; i <= n-m; i++)
    {
        ans += (C[n-m][i]*F[n-k-i]);
        ans %= MOD;
    }
    ans *= C[m][k];
    ans %= MOD;
    printf("%lld
",ans);
}

int main(void)
{
    init();
    int t,cnt = 0;
    scanf("%d",&t);
    while(t--)
    {
        printf("Case %d: ",++cnt);
        solve();
    }
    return 0;
}