Kortit II

input/code.cpp:26:16: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   26 | void print(set<auto> v) {
      |                ^~~~
input/code.cpp:31:19: warning: use of 'auto' in parameter declaration only available with '-std=c++20' or '-fconcepts'
   31 | void print(vector<auto> v) {
      |                   ^~~~

#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,std::less<int>,rb_tree_tag, tree_order_statistics_node_update> indexed_set;

#define F0R(n) for (int i=0; i<n; i++)
#define FOR(from, to) for (int i = from; i < to; i++)
#define R0F(n) for (int i = n; i>=0; --i)
#define ROF(from, to) for (int i = from; i >= to; --i)

#define ll long long
#define mod (int) (1e9 + 7)
#define vi vector<int>
#define vll vector<ll>
#define vc vector<char>
#define pii pair<int, int>
#define pci pair<char, int>
#define pll pair<ll, ll>
#define YES cout << "YES\n";
#define NO cout << "NO\n";
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using namespace std;

void print(set<auto> v) {
	for (auto it = v.begin(); it != v.end(); ++it)
		cout << *it << " ";
	cout << "\n";
}
void print(vector<auto> v) {
	for (auto it = v.begin(); it != v.end(); ++it)
		cout << *it << " ";
	cout << "\n";
}

int A, B;
pii score(vi& p2) {
    int sca=0, scb=0, n = p2.size();
    F0R (n) {
        if (p2[i]<i+1)
            ++sca;
        else if (p2[i]>i+1)
            ++scb;
    }

    return {sca, scb};
}

vi fact_mod(2001);
void build() {
    fact_mod[0] = 1;
    FOR (1, 2001)
        (fact_mod[i] = fact_mod[i-1]*i) %= mod;
}

int nCr(int n, int k) {
    if (k <= 0) return 1;
    int ans = 1;
    (ans = fact_mod[n]/(fact_mod[k]*fact_mod[n-k]) ) %= mod;
    return ans;
}

set<vi> st;
int solve(vi p2, int n, int a, int b) {
    int ans = 0;
    auto [sca, scb] = score(p2);
    if (sca == A && scb == B) {
        st.insert(p2);
        ++ans;
    }
    if (a > 0 && b > 0) {
        F0R (n-1) {
            if (p2[i] == n-i || p2[n-i-1]==i+1)
                continue;
            swap(p2[i], p2[n-i-1]);
            ans += solve(p2, n, a-1, b-1);
            // (ans += solve(p2, n, a-1, b-1)) %= mod;
            swap(p2[i], p2[n-i-1]);
        }
    }
    if (a > 0) {
        F0R (n-1) {
            if (p2[i] == n || p2[n]==i+1)
                continue;
            swap(p2[i], p2[n-1]);
            ans += solve(p2, n, a-1, b);
            // (ans += solve(p2, n, a-1, b)) %= mod;
            swap(p2[i], p2[n-1]);
        }
    }
    if (b > 0) {
        FOR (1, n) {
            if (p2[i-1] == i+1 || p2[i]==i)
                continue;
            swap(p2[i-1], p2[i]);
            ans += solve(p2, n, a, b-1);
            // (ans += solve(p2, n, a, b-1)) %= mod;
            swap(p2[i-1], p2[i]);
        }
    }

    return ans % mod;
}

void soln() {
    int n, x, y;
    cin >> n >> x >> y;
    A = x; B = y;

    if ((A==0 && B!=0) || (A!=0 && B==0)) {
        cout << "0\n";
        return;
    }

    int new_n = n-A-B;
    if (new_n < 0) {
        cout << "0\n";
        return;
    }

    vi p2(A+B);
    iota(p2.begin(), p2.end(), 1);
    solve(p2, A+B, A, B);

    int ans = st.size();
    // printf("ans1=%d\n", ans);

    ans *= nCr(n, n-A-B);
    ans %= mod;
    // printf("ans2=%d\n", ans);

    ans *= fact_mod[n];
    ans %= mod;

    cout << ans << "\n";
    // printf("ans=%d, set size=%d\n", ans, st.size());

    /*for (auto v : st) {
        auto [sca, scb] = score(v);
        cout << sca << " " << scb << endl;
        print(v);
    }*/
    st.clear();
}

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

    build();
    int tc;
    cin >> tc;
    while (tc--) soln();
    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