Submission #66972958

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Source Code Expand

#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

mint dp[1 << 20][20];
mint ndp[1 << 20][20];

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  mint to[20][20];
  rep(_, m) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    to[u][v]++;
    to[v][u]++;
  }
  mint ans;
  for (; n >= 2; n--) {
    rep(s, 1 << (n - 1)) rep(j, n - 1) dp[s][j] = 0;
    rep(v, n - 1) dp[1 << v][v] = to[n-1][v];
    while (true) {
      bool done = true;
      rep(s, 1 << (n - 1)) rep(u, n - 1) if (mint val = dp[s][u]; val.val()) {
        done = false;
        if (popcount(0U + s) == 1) {
          ans += val * (to[u][n-1]-1);
        } else {
          ans += val * to[u][n-1];
        }
        rep(v, n - 1) if (~s >> v & 1) ndp[s | 1 << v][v] += val * to[u][v];
        // cout << s << ' ' << u << ' ' << val.val() << ' ' << ans.val() << endl;
      }
      rep(s, 1 << (n - 1)) rep(u, n - 1) dp[s][u] = ndp[s][u], ndp[s][u] = 0;
      if (done) break;
    }
    // cout << ans.val() << endl;
  }
  ans /= 2;
  cout << ans.val() << '\n';
}

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