Kortit II

#include<bits/stdc++.h>
using namespace std;
#define forn(i,n) for(int i=0;i<n;++i)
#define forN(i,k,n) for(int i=k;i<n;++i)
#define pb push_back
#define F first
#define S second
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define inf ((int)(1.01e9))
#define mod ((int)(1e9+7))
#define N ((int)(102))
 
ll n, m, a, b, counter, result, fact[N], A[N][N];
unordered_map<ll,ll> mem;
vector<int> v1, v2;

ll nCr(int n, int r);
ll dcmb(int n, int a) {
    ll counter = 0; 
    forn(i, n+1) 
        if (n-i >= a) {
            counter = (counter+((i&1)?-1:1) * nCr(n,i) * A[n-i][a]) % mod; 
        }
    return counter;
}
void solve();
 
int main() {
    cin.tie(0) -> sync_with_stdio(0);
    cout.tie(0);
    fact[0] = fact[1] = 1;
    forN(i,2,N) fact[i] = ((i)*fact[i-1]) %mod;

    A[0][0] = 1;
    forN(i, 1, N) {
        A[i][0] = A[i-1][0];
        forN(k, 1, i) {
            A[i][k] = ((k+1)*A[i-1][k] + (i-k)*A[i-1][k-1])%mod;
        }
    }
 
    int t;
    cin >> t;
    while(t--) solve();
}

ll nCr(int n, int r) {
    if (!r) return 1;
    return (fact[n] / ((fact[r] * fact[n-r])%mod)) % mod;
}

void solve() {
    cin >> m >> a >> b;
    if (m < a + b || ((!b)&&a) || ((!a)&&b)) {
        cout << "0" << endl;
        return;
    }
    n = a + b;
 
    ll comb = nCr(m,m-n);
    comb = (comb*comb*fact[m-n]*fact[n])%mod;

    result = (dcmb(n, a)*comb) % mod;
    cout << result << endl;
}

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: WRONG ANSWER

Test 4

Group: 4, 5

Verdict: WRONG ANSWER

Test 5

Group: 5

Verdict: RUNTIME ERROR

Test 6

Group: 5

Verdict: RUNTIME ERROR