Submission #1442990

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Source Code Expand

// clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
// clang-format on

main {
  int n, m;
  cin >> n >> m;
  vvi v(n, vi(n));
  while (m--) {
    int x, y;
    cin >> x >> y;
    v[--x][--y] = true;
  }
  vi dp(1 << n);
  dp[0] = 1;
  rep(i, 1 << n) rep(j, n) {
    if (i >> j & 1) continue;
    bool valid = true;
    rep(k, n) valid &= !((i >> k & 1) && v[j][k]);
    if (valid) dp[i | 1 << j] += dp[i];
  }
  cout << dp.back() << endl;
}

Submission Info

Judge Result