abc183_c - Travel

using namespace std;
using ll = long long;
using ii = pair<int, int>;
using vi = vector<int>;
template <typename InputIterator,
          typename T = typename iterator_traits<InputIterator>::value_type>
void read_n(InputIterator it, int n)
{
    copy_n(istream_iterator<T>(cin), n, it);
}
template <typename InputIterator,
          typename T = typename iterator_traits<InputIterator>::value_type>
void write(InputIterator first, InputIterator last, const char *delim = "\n")
{
    copy(first, last, ostream_iterator<T>(cout, delim));
}
int main(void)
{
    ios::sync_with_stdio(false), cin.tie(NULL);
    int n, k;
    cin >> n >> k;
    vector<vi> t(n, vi(n));
    for (auto &ti : t)
        read_n(ti.begin(), n);
    vi a(n);
    for (int i = 0; i < n; ++i)
        a[i] = i;
    int ans = 0;
    do
    {
        int cur = 0;
        for (int i = 0; i < n; ++i)
            cur += t[a[i]][a[(i + 1) % n]];
        ans += cur == k;
    } while (next_permutation(a.begin() + 1, a.end()));
    cout << ans << endl;
    return 0;
}