Problem p02579 (C++)

Buggy submission (status: Runtime Error):
/**
 *    author:  Dooloper
 *    created: 16.09.2020 23:48:27
 **/

#pragma region Macros
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
using P = pair<int, int>;
using ll = long long;

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repn(i, n) for (int i = 1; i <= (n); i++)
#define pb push_back
void debug_out() { cout << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

const double PI = acos(-1);
const int mod = 1000000007;
class mint {
  long long x;

public:
  mint(long long 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;
    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;
  }

  friend ostream &operator<<(ostream &os, const mint &m) {
    os << m.x;
    return os;
  }
};
#pragma endregion

int h, w;
char maze[105][105];

const int di[] = {-1, 0, 1, 0};
const int dj[] = {0, -1, 0, 1};

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> h >> w;
  int sh, sw, gh, gw;
  cin >> sh >> sw >> gh >> gw;
  sh--;
  sw--;
  gh--;
  gw--;
  rep(i, h) rep(j, w) cin >> maze[i][j];
  const int INF = 1e9;
  vector<vector<int>> dist(h, vector<int>(w, INF));
  deque<P> q;
  dist[sh][sw] = 0;
  q.emplace_back(sh, sw);
  while (!q.empty()) {
    int i = q.front().first;
    int j = q.front().second;
    int d = dist[i][j];
    q.pop_front();
    if (dist[i][j] != d)
      continue;
    rep(v, 4) {
      int ni = i + di[v], nj = j + dj[v];
      if (ni < 0 || ni >= h || nj < 0 || nj >= w)
        continue;
      if (maze[ni][nj] == '#')
        continue;
      if (dist[ni][nj] <= d)
        continue;
      dist[ni][nj] = d;
      q.emplace_front(ni, nj);
    }
    for (int ei = -2; ei <= 2; ei++) {
      for (int ej = -2; ej <= 2; ej++) {
        int ni = i + ei, nj = j + ej;
        if (ni < 0 || ni >= h || nj < 0 || nj >= w)
          continue;
        if (maze[ni][nj] == '#')
          continue;
        if (dist[ni][nj] <= d + 1)
          continue;
        dist[ni][nj] = d + 1;
        q.emplace_back(ni, nj);
      }
    }
  }
  int ans = (dist[gh][gw] == INF) ? -1 : dist[gh][gw];
  cout << ans << endl;
  return 0;
}

Fixed submission:
/**
 *    author:  Dooloper
 *    created: 16.09.2020 23:48:27
 **/

#pragma region Macros
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
using P = pair<int, int>;
using ll = long long;

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repn(i, n) for (int i = 1; i <= (n); i++)
#define pb push_back
void debug_out() { cout << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

const double PI = acos(-1);
const int mod = 1000000007;
class mint {
  long long x;

public:
  mint(long long 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;
    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;
  }

  friend ostream &operator<<(ostream &os, const mint &m) {
    os << m.x;
    return os;
  }
};
#pragma endregion

int h, w;
char maze[1005][1005];

const int di[] = {-1, 0, 1, 0};
const int dj[] = {0, -1, 0, 1};

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> h >> w;
  int sh, sw, gh, gw;
  cin >> sh >> sw >> gh >> gw;
  sh--;
  sw--;
  gh--;
  gw--;
  rep(i, h) rep(j, w) cin >> maze[i][j];
  const int INF = 1e9;
  vector<vector<int>> dist(h, vector<int>(w, INF));
  deque<P> q;
  dist[sh][sw] = 0;
  q.emplace_back(sh, sw);
  while (!q.empty()) {
    int i = q.front().first;
    int j = q.front().second;
    int d = dist[i][j];
    q.pop_front();
    if (dist[i][j] != d)
      continue;
    rep(v, 4) {
      int ni = i + di[v], nj = j + dj[v];
      if (ni < 0 || ni >= h || nj < 0 || nj >= w)
        continue;
      if (maze[ni][nj] == '#')
        continue;
      if (dist[ni][nj] <= d)
        continue;
      dist[ni][nj] = d;
      q.emplace_front(ni, nj);
    }
    for (int ei = -2; ei <= 2; ei++) {
      for (int ej = -2; ej <= 2; ej++) {
        int ni = i + ei, nj = j + ej;
        if (ni < 0 || ni >= h || nj < 0 || nj >= w)
          continue;
        if (maze[ni][nj] == '#')
          continue;
        if (dist[ni][nj] <= d + 1)
          continue;
        dist[ni][nj] = d + 1;
        q.emplace_back(ni, nj);
      }
    }
  }
  int ans = (dist[gh][gw] == INF) ? -1 : dist[gh][gw];
  cout << ans << endl;
  return 0;
}