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

#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \\
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \\
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \\
  {                                                                            \\
    cout << #v << "=" << endl;                                                 \\
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \\
    cout << endl;                                                              \\
  }
#define mdebug(m)                                                              \\
  {                                                                            \\
    cout << #m << "=" << endl;                                                 \\
    REP(i_debug, m.size()) {                                                   \\
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \\
      cout << endl;                                                            \\
    }                                                                          \\
  }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void chOut(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;

signed main() {

  int H, W;
  cin >> H >> W;
  int ch, cw;
  cin >> ch >> cw;
  ch--;
  cw--;
  int dh, dw;
  cin >> dh >> dw;
  dh--;
  dw--;
  vector<string> S(H);
  cin >> S;

  mat dp(H, vec(W, INF));
  dp[ch][cw] = 0;
  v_Pii ls;
  queue<Pii> q1;
  q1.push(Pii(ch, cw));

  while (true) {
    queue<Pii> q2;
    while (!q1.empty()) {
      Pii p = q1.front();
      q2.push(p);
      q1.pop();

      int i = p.fi, j = p.se;
      REP(k, 4) {
        int x = i + dx[k], y = j + dy[k];
        if (x < 0 || x >= H || y < 0 || y >= W || S[x][y] == '#')
          continue;
        if (dp[x][y] == INF) {
          dp[x][y] = dp[i][j];
          q1.push(Pii(x, y));
        }
      }
    }

    while (!q2.empty()) {
      Pii p = q2.front();
      q2.pop();
      int i = p.fi, j = p.se;
      FOR(u, -2, 3) FOR(v, -2, 3) {
        int x = i + u, y = j + v;
        if (x < 0 || x >= H || y < 0 || y >= W || S[x][y] == '#')
          continue;
        if (dp[x][y] == INF) {
          dp[x][y] = dp[i][j] + 1;
          q1.push(Pii(x, y));
        }
      }
    }
    if (q1.empty())
      break;
  }

  chOut(dp[dh][dw] < INF, dp[dh][dw], -1);

  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \\
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \\
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \\
  {                                                                            \\
    cout << #v << "=" << endl;                                                 \\
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \\
    cout << endl;                                                              \\
  }
#define mdebug(m)                                                              \\
  {                                                                            \\
    cout << #m << "=" << endl;                                                 \\
    REP(i_debug, m.size()) {                                                   \\
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \\
      cout << endl;                                                            \\
    }                                                                          \\
  }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void chOut(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;

signed main() {

  int H, W;
  cin >> H >> W;
  int ch, cw;
  cin >> ch >> cw;
  ch--;
  cw--;
  int dh, dw;
  cin >> dh >> dw;
  dh--;
  dw--;
  vector<string> S(H);
  cin >> S;

  mat dp(H, vec(W, INF));
  dp[ch][cw] = 0;

  deque<Pii> que;
  que.push_back(Pii(ch * W + cw, 0));
  while (!que.empty()) {
    Pii p = que.front();
    que.pop_front();

    int i = p.fi / W, j = p.fi % W;
    if (dp[i][j] < p.se)
      continue;

    FOR(dx, -2, 3) FOR(dy, -2, 3) if (dx != 0 || dy != 0) {
      int x = i + dx, y = j + dy;
      if (x < 0 || x >= H || y < 0 || y >= W || S[x][y] == '#')
        continue;
      if (llabs(dx) + llabs(dy) == 1) {
        if (dp[x][y] > dp[i][j]) {
          dp[x][y] = dp[i][j];
          que.push_front(Pii(x * W + y, dp[x][y]));
        }
      } else {
        if (dp[x][y] > dp[i][j] + 1) {
          dp[x][y] = dp[i][j] + 1;
          que.push_front(Pii(x * W + y, dp[x][y]));
        }
      }
    }
  }
  chOut(dp[dh][dw] < INF, dp[dh][dw], -1);

  return 0;
}