Lähetit

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

using namespace std;

typedef int64_t ll;

const ll u = 1000000007;

template <typename T>
T tabs(T x)
{
    return x < 0 ? -x : x;
}

ll search(vector<bool>& a, int n, int m, int i, int k)
{
    if (k == 0) return 1;
    ll s = 0;
    for (int j = i; j < m-k+1; ++j) {
        int q = tabs(n-1-j);
        for (int l = q; l < m-q; l += 2) {
            if (a[l]) continue;
            a[l] = true;
            s += search(a,n,m,j+1,k-1);
            s %= u;
            a[l] = false;
        }
    }
    return s;
}

int main()
{
    int n, k, m;
    cin >> n >> k;
    m = n*2-1;
    if (k >= m) {
        cout << "QAQ" << endl;
        return 0;
    }
    vector<bool> a(m);
    cout << search(a,n,m,0,k) << endl;
    return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: WRONG ANSWER

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 8

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 9

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 15

Group: 3

Verdict: WRONG ANSWER