Kortit II

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

using ll  = long long;

const ll MOD = 1000000007;

ll factorial(ll n) {
    ll ans = 1;
    for (ll i = 1; i <= n; ++i) {
        ans = (ans * i) % MOD;
    }
    return ans;
}

struct game {
    ll n;
    ll a;
    ll b;
};

ll recurse(std::vector<bool>& px, ll n, ll lt, ll gt, ll max) {
    ll sum = 0;

    if (n >= max) {
        return 1;
    }

    if (lt > 0) {
        for (ll i = 0; i < n; ++i) {
            if (!px[i]) {
                px[i] = true;
                sum += recurse(px, n+1, lt-1, gt, max);
                px[i] = false;
            }
        }
    }

    if (gt > 0) {
        for (ll i = n+1; i < max; ++i) {
            if (!px[i]) {
                px[i] = true;
                sum += recurse(px, n+1, lt, gt-1, max);
                px[i] = false;
            }
        }
    }

    return sum;
}

int main() {
    ll count;
    std::cin >> count;
    std::vector<game> games{};

    for (ll i = 0; i < count; ++i) {
        ll n, a, b;

        std::cin >> n >> a >> b;
        games.push_back(game{ .n = n, .a = a, .b = b });
    }

    for (auto [n, a, b] : games) {
        if (a + b > n || ((a != b) && (a == 0 || b == 0))) {
            std::cout << 0 << "\n";
            continue;
        }


        ll total = ((factorial(n) / factorial(n-(a+b))) * (factorial(n) / factorial(a+b))) % MOD;

        std::vector<bool> px(a+b, false);
        ll sum = recurse(px, 0, a, b, a+b);

        std::cout << (sum * total) % MOD << "\n";
    }
    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: 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