Problem p02680 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;

#define REP(i, n, m) for (ll i = n; i < (ll)m; ++i)
#define IREP(i, n, m) for (ll i = n - 1; i >= m; --i)
#define rep(i, n) REP(i, 0, n)
#define irep(i, n) IREP(i, n, 0)
#define all(v) v.begin(), v.end()
#define vprint(v)                                                              \
  for (auto e : v) {                                                           \
    cout << e << " ";                                                          \
  };                                                                           \
  cout << endl;
#define vvprint(vv)                                                            \
  for (auto v : vv) {                                                          \
    vprint(v)                                                                  \
  };

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(20);

  ll N, M;
  cin >> N >> M;
  vll A(N), B(N), C(N);
  vll D(M), E(M), F(M);
  rep(i, N) cin >> A[i] >> B[i] >> C[i];
  rep(i, M) cin >> D[i] >> E[i] >> F[i];

  set<ll> xs = {0}, ys = {0};
  rep(i, N) {
    xs.insert(A[i]);
    xs.insert(B[i]);
    ys.insert(C[i]);
  }
  rep(i, M) {
    ys.insert(E[i]);
    ys.insert(F[i]);
    xs.insert(D[i]);
  }
  unordered_map<ll, ll> xm, ym;
  vll xv(xs.size()), yv(ys.size());
  ll idx = 0;
  for (ll x : xs) {
    xm[x] = idx;
    xv[idx++] = x;
  }
  idx = 0;
  for (ll y : ys) {
    ym[y] = idx;
    yv[idx++] = y;
  }

  vvll m(ys.size() * 2, vll(xs.size() * 2, 0));
  rep(i, N) REP(j, xm[A[i]] * 2, xm[B[i]] * 2 + 1) m[ym[C[i]] * 2][j] = 1;
  rep(i, M) REP(j, ym[E[i]] * 2, ym[F[i]] * 2 + 1) m[j][xm[D[i]] * 2] = 1;

  ll cx = xm[0] * 2, cy = ym[0] * 2, a = 0;
  ll xmax = xs.size() * 2 - 2, ymax = ys.size() * 2 - 2;
  vvll dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
  vll ws(xs.size()), hs(ys.size());
  rep(i, xs.size() - 1) ws[i] = xv[i + 1] - xv[i];
  rep(i, ys.size() - 1) hs[i] = yv[i + 1] - yv[i];
  queue<pair<ll, ll>> q;
  q.push({cx, cy});
  m[cy][cx] = 1;
  while (!q.empty()) {
    auto p = q.front();
    q.pop();
    if (p.first == 0 || p.first == xmax || p.second == 0 || p.second == ymax) {
      cout << "INF" << endl;
      return 0;
    }
    if (p.first % 2 == 1 && p.second % 2 == 1)
      a += ws[p.first / 2] * hs[p.second / 2];
    for (auto d : dirs) {
      ll nx = p.first + d[0], ny = p.second + d[1];
      if (!m[ny][nx])
        q.push({nx, ny}), m[ny][nx] = 1;
    }
  }
  cout << a << endl;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;

#define REP(i, n, m) for (ll i = n; i < (ll)m; ++i)
#define IREP(i, n, m) for (ll i = n - 1; i >= m; --i)
#define rep(i, n) REP(i, 0, n)
#define irep(i, n) IREP(i, n, 0)
#define all(v) v.begin(), v.end()
#define vprint(v)                                                              \
  for (auto e : v) {                                                           \
    cout << e << " ";                                                          \
  };                                                                           \
  cout << endl;
#define vvprint(vv)                                                            \
  for (auto v : vv) {                                                          \
    vprint(v)                                                                  \
  };

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(20);

  ll N, M;
  cin >> N >> M;
  vll A(N), B(N), C(N);
  vll D(M), E(M), F(M);
  rep(i, N) cin >> A[i] >> B[i] >> C[i];
  rep(i, M) cin >> D[i] >> E[i] >> F[i];

  set<ll> xs = {0}, ys = {0};
  rep(i, N) {
    xs.insert(A[i]);
    xs.insert(B[i]);
    ys.insert(C[i]);
  }
  rep(i, M) {
    ys.insert(E[i]);
    ys.insert(F[i]);
    xs.insert(D[i]);
  }
  unordered_map<ll, ll> xm, ym;
  vll xv(xs.size()), yv(ys.size());
  ll idx = 0;
  for (ll x : xs) {
    xm[x] = idx;
    xv[idx++] = x;
  }
  idx = 0;
  for (ll y : ys) {
    ym[y] = idx;
    yv[idx++] = y;
  }

  vector<vector<bool>> m(ys.size() * 2, vector<bool>(xs.size() * 2, 0));
  rep(i, N) REP(j, xm[A[i]] * 2, xm[B[i]] * 2 + 1) m[ym[C[i]] * 2][j] = 1;
  rep(i, M) REP(j, ym[E[i]] * 2, ym[F[i]] * 2 + 1) m[j][xm[D[i]] * 2] = 1;

  ll cx = xm[0] * 2, cy = ym[0] * 2, a = 0;
  ll xmax = xs.size() * 2 - 2, ymax = ys.size() * 2 - 2;
  vvll dirs = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
  vll ws(xs.size()), hs(ys.size());
  rep(i, xs.size() - 1) ws[i] = xv[i + 1] - xv[i];
  rep(i, ys.size() - 1) hs[i] = yv[i + 1] - yv[i];
  queue<pair<ll, ll>> q;
  q.push({cx, cy});
  m[cy][cx] = 1;
  while (!q.empty()) {
    auto p = q.front();
    q.pop();
    if (p.first == 0 || p.first == xmax || p.second == 0 || p.second == ymax) {
      cout << "INF" << endl;
      return 0;
    }
    if (p.first % 2 == 1 && p.second % 2 == 1)
      a += ws[p.first / 2] * hs[p.second / 2];
    for (auto d : dirs) {
      ll nx = p.first + d[0], ny = p.second + d[1];
      if (!m[ny][nx])
        q.push({nx, ny}), m[ny][nx] = 1;
    }
  }
  cout << a << endl;
}