Kortit II

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const ll MOD=1000000007;
const ll N=2009;

ll C[N][N];

ll P(ll n,ll m){
	ll res=1;
	for(ll i=n;i>n-m;i--){
		res*=i;
		res%=MOD;
	}
	return res;
}
void M(ll&a,ll b){
	a=a*b%MOD;
}

ll ans=1;
ll base[N];
ll dp[N][N];

void query(ll n,ll a,ll b){
	if(a<b)swap(a,b);
	ll c=a+b;
	for(ll i=a;i<=c;i++){
		ll sum=0;
		for(ll j=0;j<i-a;j++){
			sum+=(base[j]*C[i][j+a])%MOD;
			sum%=MOD;
		}
		base[i-a]=(dp[i][a]+MOD-sum)%MOD;
	}
	ans=ans*base[b]%MOD;
	ans=ans*P(n,n)%MOD;
	cout<<ans%MOD<<endl;
}

int main(){
	for(int i=0;i<=2000;i++)C[i][0]=1;
	for(int i=1;i<=2000;i++){
		for(int j=1;j<=i;j++){
			C[i][j]=(C[i-1][j-1]+C[i-1][j])%MOD;
		}
	}
	for(ll i=1;i<=2005;i++){
        dp[i][0]=1;
        dp[i][i]=0;
        for(ll j=1;j<i;j++){
        	dp[i][j]+=((j+1)*dp[i-1][j]+(i-j)*dp[i-1][j-1]);
        	dp[i][j]%=MOD;
		}
    }
	ll Q;
	cin>>Q;
	while(Q--){
		ans=1;
		memset(base,0,sizeof(base));
		ll n,a,b;
		cin>>n>>a>>b;
		ll c=a+b;
		if(a==0&&b==0){
			cout<<P(n,n)%MOD<<endl;
			continue;
		}
		else if(c>n){
			cout<<0<<endl;
			continue;
		}
		else if(c<n){
			ans=ans*C[n][c]%MOD;
		}
		query(n,a,b);
	}
	return 0;
}

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