Kortit II

input/code.cpp: In function 'void solve()':
input/code.cpp:27:29: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |     for (long long i = 0; i < B.size(); i++) {
      |                           ~~^~~~~~~~~~

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

long long ans = 0;
long long n, a, b;
vector<long long> A;
vector<long long> B;
vector<bool> used;

long long fact(long long x) {
    if (x == 0) {
        return 1;
    }
    return x * fact(x - 1);
}

long long C(long long n, long long k) {
    return fact(n) / fact(k) / fact(n - k);
}

void solve() {
    int cntA = 0;
    int cntB = 0;
    for (long long i = 0; i < B.size(); i++) {
        if (A[i] > B[i]) {
            cntA++;
        } else if (B[i] > A[i]) {
            cntB++;
        }
    }
    if (cntA > a || cntB > b) {
        return;
    }
    if (B.size() == A.size()) {
        if (cntA == a && cntB == b) {
            ans++;
        }
        return;
    }
    for (long long i = 1; i <= a + b; i++) {
        if (!used[i]) {
            B.push_back(i);
            used[i] = true;
            solve();
            used[i] = false;
            B.pop_back();
        }
    }
}

int main() {
    long long T;
    cin >> T;
    for (long long t = 0; t < T; t++) {
        ans = 0;
        cin >> n >> a >> b;
        if (n < a + b) {
            cout << 0 << '\n';
            continue;
        }
        B.clear();
        A.resize(a + b);
        for (long long i = 1; i <= a + b; i++) {
            A[i - 1] = i;
        }
        used.resize(a + b + 1, false);
        solve();
        ans *= fact(n);
        ans %= 1000000007;
        ans *= C(n, n - a - b);
        ans %= 1000000007;
        cout << ans << '\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: TIME LIMIT EXCEEDED

Test 4

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 5

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 6

Group: 5

Verdict: TIME LIMIT EXCEEDED