Kortit II

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <iterator>
#include <iomanip>
#include <list>
#include <numeric>
 
using namespace std;
 
 
int mod_factorial(int n) {
    long long result = 1;
    for (int i = 2; i <= n; ++i) {
        result = (result * i) % 1000000007;
    }
    return result;
}
long long factorial(int n) {
    long long result = 1;
    for (int i = 2; i <= n; ++i) {
        result *= i;
    }
    return result;
}
 
long long nCr(int n, int k) {
    long long result = mod_factorial(n)/mod_factorial(n-k);
    return result;
}
 
vector<int> ith_permutation(const vector<int>& l, int i) {
    int n = l.size();
    vector<long long> fact(n, 1);
    vector<int> perm(n, 0);
 
    for (int k = 1; k < n; ++k) {
        fact[k] = fact[k - 1] * k;
    }
 
    for (int k = 0; k < n; ++k) {
        perm[k] = i / fact[n - 1 - k];
        i = i % fact[n - 1 - k];
    }
 
    for (int k = n - 1; k > 0; --k) {
        for (int j = k - 1; j >= 0; --j) {
            if (perm[j] <= perm[k]) {
                perm[k]++;
            }
        }
    }
 
    vector<int> result;
    for (int x : perm) {
        result.push_back(l[x]);
    }
    return result;
}
 
int main() {
    int t;
    cin >> t;
 
    vector<vector<int>> vals(t);
    for (int test = 0; test < t; ++test) {
        int n, a, b;
        cin >> n >> a >> b;
        vals[test] = {n, a, b};
    }
 
    for (const auto& test : vals) {
        int n = test[0], a = test[1], b = test[2];
        if (a + b == 1 || a + b > n) {
            cout << 0 << endl;
            continue;
        }
        if (a+b == n && a==b) {
            cout << mod_factorial(n) << "\n";
            continue;
        }
        a=std::max(a, b);
        b=std::min(a, b);
        int possibles = 0;
        int apb = a + b;
        int _fac = factorial(apb) - 1;
        vector<int> draws(n - apb);
        iota(draws.begin(), draws.end(), 0);
        vector<int> pairs(n);
        iota(pairs.begin(), pairs.end(), 0);
 
        sort(draws.rbegin(), draws.rend());
        for (int draw : draws) {
            pairs.erase(pairs.begin() + draw);
        }
 
        int i = _fac;
        while (i >= 0) {
            vector<int> perm = ith_permutation(pairs, i);
            int A = 0, B = 0;
            for (int j = 0; j < apb; j++) {
                if (perm[j] < pairs[j]) {
                    A++;
                } else if (perm[j] > pairs[j]) {
                    B++;
                }
 
                if (A > a || B > b || (A <= a && B <= b && j == apb - 1)) {
                    i -= factorial(apb - j - 1);
                    break;
                }
            }
 
            if (A == a && B == b) {
                possibles++;
            }
        }
        
 
        possibles = (((possibles * mod_factorial(n)) % 1000000007) * nCr(n, n-apb)) % 1000000007;
        cout << possibles << "\n";
    }
 
    return 0;
}

Test 1

Group: 1, 2, 3, 4, 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()

Test 2

Group: 2, 3, 4, 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()

Test 3

Group: 3, 4, 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()

Test 4

Group: 4, 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()

Test 5

Group: 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()

Test 6

Group: 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::length_error'
  what():  cannot create std::vector larger than max_size()