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\n",ans);
}

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