Kortit II

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define N 2001
#define M 1000000007

int t,n,a,b;
ll C[N][N],ncr[N][N],F[N];

int main(){
	cin.tie(0)->sync_with_stdio(0);

	F[0]=1;
	for(int i=1;i<N;++i) F[i]=i*F[i-1]%M;

	for(int i=0;i<N;++i){
		ncr[i][0]=1;
		for(int j=1;j<=i;++j) ncr[i][j]=(ncr[i-1][j-1]+ncr[i-1][j])%M;
	}

	for(int n=0;n<N;++n){
		C[n][0]=1;
		for(int k=1;k<=n;++k) C[n][k]=((k+1)*C[n-1][k]+(n-k)*C[n-1][k-1])%M;
	}

	cin>>t;
	while(t--){
		cin>>n>>a>>b;
		if(a+b>n){
			cout<<"0\n";
			continue;
		}
		ll r=0;
		for(int i=0,j=1-2*((a+b)&1);i<=a+b;++i,j*=-1){
			r+=M+ncr[a+b][i]*C[i][a]%M*j;
			r%=M;
		}
		r=r*ncr[n][n-a-b]%M*F[n]%M;
		cout<<r<<'\n';
	}
}

Test 1

Group: 1, 2, 3, 4, 5

Verdict: ACCEPTED

Test 2

Group: 2, 3, 4, 5

Verdict: ACCEPTED

Test 3

Group: 3, 4, 5

Verdict: ACCEPTED

Test 4

Group: 4, 5

Verdict: ACCEPTED

Test 5

Group: 5

Verdict: ACCEPTED

Test 6

Group: 5

Verdict: ACCEPTED