Problem p02579 (C++) — buggy submission, verdict: Time Limit Exceeded

#ifdef LOCAL
#define _GLIBCXX_DEBUG
#define __clock__
#else
#pragma GCC optimize("Ofast")
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;
using PII = pair<ll, ll>;

// tourist set
template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\\n'; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

#define FOR(i, a, b) for (ll i = (a); i < (b); ++i)
#define rep(i, b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout << (s) << '\\n'
#define p2(s, t) cout << (s) << " " << (t) << '\\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\\n'
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())
#define MP make_pair
#define p_yes() p("YES")
#define p_no() p("NO")
#define possible() p("Possible")
#define impossible() p("Impossible")

ll SUM(VI &V) { return accumulate(ALL(V), 0LL); }

ll MIN(VI &V) { return *min_element(ALL(V)); }
ll MAX(VI &V) { return *max_element(ALL(V)); }

void print_vector(VI &V) {
  ll n = V.size();
  rep(i, n) {
    if (i)
      cout << ' ';
    cout << V[i];
  }
  cout << endl;
}

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll a, ll b) {
  ll g = gcd(a, b);
  return a / g * b;
}

// long double
using ld = long double;
#define EPS (1e-14)
#define equals(a, b) (fabs((a) - (b)) < EPS)

void no() {
  p_no();
  exit(0);
}
void yes() {
  p_yes();
  exit(0);
}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);

// snuke's mint
// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
// const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
};

struct Edge {
  ll to;
  ll cost;
  Edge(ll to, ll cost) : to(to), cost(cost) {}
  Edge() {
    to = 0;
    cost = 0;
  }
};

struct Node {
  ll distance;
  ll index;
  Node(ll d, ll i) {
    distance = d;
    index = i;
  }
  Node() {}

  bool operator<(const Node &another) const {
    return distance < another.distance;
  }
  bool operator>(const Node &another) const {
    return distance > another.distance;
  }
};

struct Dijkstra {
  vector<ll> d;
  vector<vector<Edge>> graph;
  vector<bool> done;

  // ノード数を入れる
  void initialize(ll size) {
    d.resize(size);
    done.resize(size);
    graph.resize(size);
    reset();
  }

  void reset() {
    ll N = graph.size();
    FOR(i, 0, N) {
      d[i] = inf;
      done[i] = false;
    }
  }

  ll distance(int i) {
    if ((ll)d.size() <= i)
      return -1;
    return d[i];
  }

  void print_graph() {
    FOR(i, 0, (ll)graph.size()) {
      cout << i << " -> ";

      for (auto edge : graph[i]) {
        cout << edge.to << " ";
      }
      cout << endl;
    }
    p("distance");
    FOR(i, 0, (ll)graph.size()) {
      ll d = distance(i);
      cout << i << " " << d << endl;
    }
  }

  void register_edge(ll a, ll b, ll cost) {
    if (cost < 0) {
      p("ダイクストラなのに負コストですがいいですか？");
      exit(0);
    }
    auto edge = Edge(b, cost);
    graph[a].push_back(edge);
  }

  // 双方向
  void register_edge2(ll a, ll b, ll cost) {
    register_edge(a, b, cost);
    register_edge(b, a, cost);
  }

  void calc_shortest_path(ll from = 0) {
    ll N = graph.size();
    if (from < 0 || from >= N) {
      cout << "index error" << endl;
      exit(0);
    }
    priority_queue<Node, vector<Node>, greater<Node>> que;
    auto node = Node();
    // 始点
    node.index = from;
    node.distance = 0;
    que.push(node);

    while (!que.empty()) {
      // 1番distanceが小さいノード
      Node n = que.top();
      que.pop();

      if (done[n.index]) {
        continue;
      }

      done[n.index] = true;
      d[n.index] = n.distance;

      auto edge_list = graph[n.index];
      for (auto edge : edge_list) {
        // 短くなるノードがあれば
        if (!done[edge.to] && n.distance + edge.cost < d[edge.to]) {
          ll shorter_distance = n.distance + edge.cost;
          que.push(Node(shorter_distance, edge.to));
        }
      }
    }
  }
};

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

ll H, W;
VV G;

bool in_range(ll i, ll j) {
  if (0 <= i && i < H && 0 <= j && j < W) {
    return true;
  } else {
    return false;
  }
}

void bfs_fill(ll y, ll x, ll v) {
  queue<PII> que;
  que.push({y, x});
  while (!que.empty()) {
    auto pa = que.front();
    que.pop();
    G[pa.first][pa.second] = v; // paint
    rep(i, 4) {
      ll ny = pa.first + dy[i];
      ll nx = pa.second + dx[i];
      if (in_range(ny, nx) && G[ny][nx] == -1 && G[ny][nx] != inf) {
        que.push(MP(ny, nx));
      }
    }
  }
  return;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  // input
  cin >> H >> W;
  ll startY, startX;
  cin >> startY >> startX;
  startY--;
  startX--;

  ll destY, destX;
  cin >> destY >> destX;
  destY--;
  destX--;

  vector<string> S(H);
  rep(i, H) cin >> S[i];

  VV dist(H, VI(W, inf));

  deque<PII> que;
  dist[startY][startX] = 0;
  que.push_back({startY, startX});

  while (!que.empty()) {
    auto pa = que.front();
    que.pop_front();
    ll y = pa.first;
    ll x = pa.second;
    ll d = dist[y][x];

    rep(i, 4) {
      ll ny = y + dy[i];
      ll nx = x + dx[i];
      if (!in_range(ny, nx))
        continue;
      if (S[ny][nx] == '#')
        continue;
      if (dist[ny][nx] > d) {
        // 距離0
        dist[ny][nx] = d;
        que.push_front({ny, nx});
      }
    }

    FOR(i, -2, 3) {
      FOR(j, -2, 3) {
        ll ny = y + i;
        ll nx = x + j;
        if (!in_range(ny, nx))
          continue;
        if (S[ny][nx] == '#')
          continue;
        if (dist[ny][nx] > d + 1) {
          // 距離1
          dist[ny][nx] = d + 1;
          que.push_back({ny, nx});
        }
      }
    }
  }

  // for(VI V : dist){
  //   print_vector(V);
  // }

  ll ans = dist[destY][destX];
  if (ans == inf) {
    p(-1);
  } else {
    p(ans);
  }

  return 0;
}

Error: TLE

Fixed submission:

#ifdef LOCAL
#define _GLIBCXX_DEBUG
#define __clock__
#else
#pragma GCC optimize("Ofast")
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;
using PII = pair<ll, ll>;

// tourist set
template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\\n'; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

#define FOR(i, a, b) for (ll i = (a); i < (b); ++i)
#define rep(i, b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout << (s) << '\\n'
#define p2(s, t) cout << (s) << " " << (t) << '\\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\\n'
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())
#define MP make_pair
#define p_yes() p("YES")
#define p_no() p("NO")
#define possible() p("Possible")
#define impossible() p("Impossible")

ll SUM(VI &V) { return accumulate(ALL(V), 0LL); }

ll MIN(VI &V) { return *min_element(ALL(V)); }
ll MAX(VI &V) { return *max_element(ALL(V)); }

void print_vector(VI &V) {
  ll n = V.size();
  rep(i, n) {
    if (i)
      cout << ' ';
    cout << V[i];
  }
  cout << endl;
}

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll a, ll b) {
  ll g = gcd(a, b);
  return a / g * b;
}

// long double
using ld = long double;
#define EPS (1e-14)
#define equals(a, b) (fabs((a) - (b)) < EPS)

void no() {
  p_no();
  exit(0);
}
void yes() {
  p_yes();
  exit(0);
}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);

// snuke's mint
// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
// const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
};

struct Edge {
  ll to;
  ll cost;
  Edge(ll to, ll cost) : to(to), cost(cost) {}
  Edge() {
    to = 0;
    cost = 0;
  }
};

struct Node {
  ll distance;
  ll index;
  Node(ll d, ll i) {
    distance = d;
    index = i;
  }
  Node() {}

  bool operator<(const Node &another) const {
    return distance < another.distance;
  }
  bool operator>(const Node &another) const {
    return distance > another.distance;
  }
};

struct Dijkstra {
  vector<ll> d;
  vector<vector<Edge>> graph;
  vector<bool> done;

  // ノード数を入れる
  void initialize(ll size) {
    d.resize(size);
    done.resize(size);
    graph.resize(size);
    reset();
  }

  void reset() {
    ll N = graph.size();
    FOR(i, 0, N) {
      d[i] = inf;
      done[i] = false;
    }
  }

  ll distance(int i) {
    if ((ll)d.size() <= i)
      return -1;
    return d[i];
  }

  void print_graph() {
    FOR(i, 0, (ll)graph.size()) {
      cout << i << " -> ";

      for (auto edge : graph[i]) {
        cout << edge.to << " ";
      }
      cout << endl;
    }
    p("distance");
    FOR(i, 0, (ll)graph.size()) {
      ll d = distance(i);
      cout << i << " " << d << endl;
    }
  }

  void register_edge(ll a, ll b, ll cost) {
    if (cost < 0) {
      p("ダイクストラなのに負コストですがいいですか？");
      exit(0);
    }
    auto edge = Edge(b, cost);
    graph[a].push_back(edge);
  }

  // 双方向
  void register_edge2(ll a, ll b, ll cost) {
    register_edge(a, b, cost);
    register_edge(b, a, cost);
  }

  void calc_shortest_path(ll from = 0) {
    ll N = graph.size();
    if (from < 0 || from >= N) {
      cout << "index error" << endl;
      exit(0);
    }
    priority_queue<Node, vector<Node>, greater<Node>> que;
    auto node = Node();
    // 始点
    node.index = from;
    node.distance = 0;
    que.push(node);

    while (!que.empty()) {
      // 1番distanceが小さいノード
      Node n = que.top();
      que.pop();

      if (done[n.index]) {
        continue;
      }

      done[n.index] = true;
      d[n.index] = n.distance;

      auto edge_list = graph[n.index];
      for (auto edge : edge_list) {
        // 短くなるノードがあれば
        if (!done[edge.to] && n.distance + edge.cost < d[edge.to]) {
          ll shorter_distance = n.distance + edge.cost;
          que.push(Node(shorter_distance, edge.to));
        }
      }
    }
  }
};

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

ll H, W;
VV G;

bool in_range(ll i, ll j) {
  if (0 <= i && i < H && 0 <= j && j < W) {
    return true;
  } else {
    return false;
  }
}

void bfs_fill(ll y, ll x, ll v) {
  queue<PII> que;
  que.push({y, x});
  while (!que.empty()) {
    auto pa = que.front();
    que.pop();
    G[pa.first][pa.second] = v; // paint
    rep(i, 4) {
      ll ny = pa.first + dy[i];
      ll nx = pa.second + dx[i];
      if (in_range(ny, nx) && G[ny][nx] == -1 && G[ny][nx] != inf) {
        que.push(MP(ny, nx));
      }
    }
  }
  return;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  // input
  cin >> H >> W;
  ll startY, startX;
  cin >> startY >> startX;
  startY--;
  startX--;

  ll destY, destX;
  cin >> destY >> destX;
  destY--;
  destX--;

  vector<string> S(H);
  rep(i, H) cin >> S[i];

  G.resize(H, VI(W, -1)); // -1 empty
  rep(i, H) {
    rep(j, W) {
      if (S[i][j] == '#')
        G[i][j] = inf;
    }
  }

  ll cnt = 0;
  rep(i, H) {
    rep(j, W) {
      if (G[i][j] == -1) {
        bfs_fill(i, j, cnt);
        cnt++;
      }
    }
  }

  debug(cnt);

  bool has_wall[1050][1050];
  rep(i, H) {
    rep(j, W) {
      rep(k, 4) {
        ll ny = i + dy[k];
        ll nx = j + dx[k];
        if (in_range(ny, nx) && G[ny][nx] == inf)
          has_wall[i][j] = 1;
      }
    }
  }

  ll N = cnt;
  Dijkstra dij;
  dij.initialize(N);

  // set<PII> se;
  map<ll, set<ll>> mp;
  rep(i, H){rep(j, W){if (G[i][j] == inf) continue;
  if (!has_wall[i][j])
    continue;
  FOR(k, -2, 3) {
    FOR(l, -2, 3) {
      ll ny = i + k;
      ll nx = j + l;
      if (!in_range(ny, nx))
        continue;
      if (G[ny][nx] == inf)
        continue;
      if (G[ny][nx] == G[i][j])
        continue;
      ll from = G[i][j];
      ll to = G[ny][nx];
      if (from > to)
        swap(from, to);
      // se.insert({from,to});
      mp[from].insert(to);
    }
  }
}
}
// debug(se);

// for(VI V : G){
//   print_vector(V);
// }

{
  // dfs
  VV F(N);
  // for(auto pa : se){
  //   ll a = pa.first;
  //   ll b = pa.second;
  //   F[a].push_back(b);
  //   F[b].push_back(a);
  // }
  for (auto pa : mp) {
    ll v = pa.first;
    set<ll> se = pa.second;
    for (ll to : se) {
      F[v].push_back(to);
      F[to].push_back(v);
    }
  }

  VI dist(N, inf);
  ll start_id = G[startY][startX];
  ll goal_id = G[destY][destX];
  debug(start_id, goal_id);
  queue<ll> que;
  que.push(start_id);
  dist[start_id] = 0;
  while (!que.empty()) {
    ll a = que.front();
    que.pop();
    for (ll to : F[a]) {
      if (dist[to] == inf) {
        que.push(to);
        dist[to] = dist[a] + 1;
      }
    }
  }

  ll ans = dist[goal_id];
  if (ans == inf) {
    p(-1);
  } else {
    p(ans);
  }
  return 0;
}

// for(auto pa : se){
//   ll from = pa.first;
//   ll to = pa.second;
//   dij.register_edge2(from,to,1);
// }

// ll start_id = G[startY][startX];
// ll goal_id = G[destY][destX];
// dij.calc_shortest_path(start_id);
// ll d = dij.distance(goal_id);
// debug(start_id, goal_id);

// if(d==inf){
//   p(-1);
// }else{
//   p(d);
// }

return 0;
}