Kortit II

#include <iostream>
#include <vector>
#include <bitset>
#include <algorithm>
#include <numeric>

using namespace std;

const int MAX_N = 2000;
const int MOD = 1e9 + 7;

long long count_games(int n, int target_a, int target_b)
{
    vector<int> p1(n), p2(n);
    bitset<MAX_N + 1> used1, used2;
    vector<int> p1_wins(n, 0), p2_wins(n, 0);
    long long count = 0;

    function<void(int)> backtrack = [&](int pos)
    {
        if (pos == n)
        {
            if (std::accumulate(p1_wins.begin(), p1_wins.end(), 0) == target_a &&
                std::accumulate(p2_wins.begin(), p2_wins.end(), 0) == target_b)
            {
                count = (count + 1) % MOD;
            }
            return;
        }

        for (int i = 1; i <= n; ++i)
        {
            if (!used1[i])
            {
                p1[pos] = i;
                used1[i] = true;

                for (int j = 1; j <= n; ++j)
                {
                    if (!used2[j])
                    {
                        p2[pos] = j;
                        used2[j] = true;

                        if (i > j)
                            p1_wins[pos] = 1;
                        else if (i < j)
                            p2_wins[pos] = 1;
                        else
                            p1_wins[pos] = p2_wins[pos] = 0;

                        backtrack(pos + 1);

                        used2[j] = false;
                        p1_wins[pos] = p2_wins[pos] = 0;
                    }
                }

                used1[i] = false;
            }
        }
    };

    backtrack(0);
    return count;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;

    while (t--)
    {
        int n, a, b;
        cin >> n >> a >> b;

        long long result = count_games(n, a, b);
        cout << result << '\n';
    }

    return 0;
}

Test 1

Group: 1, 2, 3, 4, 5

Verdict: ACCEPTED

Test 2

Group: 2, 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

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