Problem p03174 (C++)

Buggy submission (status: Memory Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define rrep(i, n) for (int(i) = ((n)-1); (i) >= 0; (i)--)
#define itn int
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
const long long INF = 1LL << 60;
const int MOD = 1000000007;
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
// https://www.creativ.xyz/dump-cpp-652/
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)

// vector
template <typename T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &x : vec)
    is >> x;
  return is;
}
// pair
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
  os << "(" << pair_var.first << ", " << pair_var.second << ")";
  return os;
}
// vector
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "{";
  for (int i = 0; i < vec.size(); i++) {
    os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
  }
  os << "}";
  return os;
}
// map
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
  os << "{";
  repi(itr, map_var) {
    os << *itr;
    itr++;
    if (itr != map_var.end())
      os << ", ";
    itr--;
  }
  os << "}";
  return os;
}
// set
template <typename T> ostream &operator<<(ostream &os, set<T> &set_var) {
  os << "{";
  repi(itr, set_var) {
    os << *itr;
    itr++;
    if (itr != set_var.end())
      os << ", ";
    itr--;
  }
  os << "}";
  return os;
}

#define DUMPOUT cerr

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&...tail) {
  DUMPOUT << head;
  if (sizeof...(Tail) > 0) {
    DUMPOUT << ", ";
  }
  dump_func(std::move(tail)...);
}

#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
  DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                              \
          << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl  \
          << "    ",                                                           \
      dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
vector<vector<int>> data(22, vector<int>(21));
vector<vector<int>> dp(25, vector<int>((1LL << 22)));
vector<vector<int>> vis(25, vector<int>((1LL << 22)));
int n;
int solve(int x, int bit) {
  if (vis[x][bit])
    return dp[x][bit];
  else
    vis[x][bit] = true;
  if (x == 0 && bit == 0)
    return dp[x][bit] = 1;
  if (dp[x][bit])
    return dp[x][bit];
  rep(y, n) {
    if (data[x - 1][y] && (bit & (1LL << y))) {
      dp[x][bit] += solve(x - 1, bit & (~(1LL << y)));
      dp[x][bit] %= MOD;
    }
  }
  return dp[x][bit];
}
signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  rep(i, n) {
    rep(j, n) { cin >> data[i][j]; }
  }
  dp[0][0] = 1;
  cout << solve(n, (1LL << n) - 1) << endl;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define rrep(i, n) for (int(i) = ((n)-1); (i) >= 0; (i)--)
#define itn int
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
const long long INF = 1LL << 60;
const int MOD = 1000000007;
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
// https://www.creativ.xyz/dump-cpp-652/
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)

// vector
template <typename T> istream &operator>>(istream &is, vector<T> &vec) {
  for (T &x : vec)
    is >> x;
  return is;
}
// pair
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
  os << "(" << pair_var.first << ", " << pair_var.second << ")";
  return os;
}
// vector
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "{";
  for (int i = 0; i < vec.size(); i++) {
    os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
  }
  os << "}";
  return os;
}
// map
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
  os << "{";
  repi(itr, map_var) {
    os << *itr;
    itr++;
    if (itr != map_var.end())
      os << ", ";
    itr--;
  }
  os << "}";
  return os;
}
// set
template <typename T> ostream &operator<<(ostream &os, set<T> &set_var) {
  os << "{";
  repi(itr, set_var) {
    os << *itr;
    itr++;
    if (itr != set_var.end())
      os << ", ";
    itr--;
  }
  os << "}";
  return os;
}

#define DUMPOUT cerr

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&...tail) {
  DUMPOUT << head;
  if (sizeof...(Tail) > 0) {
    DUMPOUT << ", ";
  }
  dump_func(std::move(tail)...);
}

#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
  DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                              \
          << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl  \
          << "    ",                                                           \
      dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
vector<vector<int>> data(22, vector<int>(21));
vector<vector<int>> dp(23, vector<int>((1LL << 21)));
vector<vector<int>> vis(23, vector<int>((1LL << 21)));
int n;
int solve(int x, int bit) {
  if (vis[x][bit])
    return dp[x][bit];
  else
    vis[x][bit] = true;
  if (x == 0 && bit == 0)
    return dp[x][bit] = 1;
  if (dp[x][bit])
    return dp[x][bit];
  rep(y, n) {
    if (data[x - 1][y] && (bit & (1LL << y))) {
      dp[x][bit] += solve(x - 1, bit & (~(1LL << y)));
      dp[x][bit] %= MOD;
    }
  }
  return dp[x][bit];
}
signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  rep(i, n) {
    rep(j, n) { cin >> data[i][j]; }
  }
  dp[0][0] = 1;
  cout << solve(n, (1LL << n) - 1) << endl;
}