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

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <ctime>
#include <deque>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <stdlib.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

/*
#pragma GCC target("avx2") //AtCoderでは "avx" にする
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
*/

#define int long long
#define endl "\\n"
#define all(v) v.begin(), v.end()
#define fir first
#define sec second
#define m_p make_pair
#define m_t make_tuple
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef pair<int, int> P;
typedef long double ld;
typedef long long ll;
template <class T> using PQ_inv = priority_queue<T, vector<T>, greater<T>>;

const double pai = 3.1415926535897;
const ll mod = 1000000007;
const int INF = 1000000021;
const ll LINF = 2000000000000000000;
const int MAX = 510000;
const ll MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
// n個を1個以上のx組のグループに分ける重複組み合わせはcom(n-1,x-1)
long long COM(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll PER(int n, int k) {
  if (n < 0 || k < 0)
    return 0;
  if (n < k)
    return fac[n];
  return fac[n] * finv[n - k] % mod;
}

long long modinv(long long a, long long m) {
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
long long modpow(int a, int n) {
  int res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

struct edge {
  int to, cost;
};
edge m_e(int xx, int yy) {
  edge ed;
  ed.to = xx;
  ed.cost = yy;
  return ed;
}
// x未満の要素数を返す二分探索関数
int b_s(vector<int> &vec, int xx) {
  return lower_bound(all(vec), xx) - vec.begin();
}
template <class T> void vecout(vector<T> &vec) {
  for (T t : vec)
    cout << t << " ";
  cout << endl;
}
template <class T> void vecin(vector<T> &vec) {
  for (int i = 0; i < vec.size(); i++)
    cin >> vec[i];
}
bool chmax(int &xx, int yy) {
  if (xx < yy) {
    xx = yy;
    return true;
  }
  return false;
}
bool chmin(int &xx, int yy) {
  if (xx > yy) {
    xx = yy;
    return true;
  }
  return false;
}
double dist(int x, int y) { return sqrt(x * x + y * y); }
double dist(int xx1, int xx2, int yy1, int yy2) {
  return sqrt(abs(xx1 - xx2) * abs(xx1 - xx2) +
              abs(yy1 - yy2) * abs(yy1 - yy2));
}
ll mypow(int nn, int kk) {
  ll xx = 1;
  rep(i, kk) { xx *= nn; }
  return xx;
}
int gcd(int xx, int yy) {
  int p = xx;
  int q = yy;
  if (q > p)
    swap(p, q);
  while (p % q != 0) {
    p %= q;
    swap(p, q);
  }
  return q;
}
int lcm(int xx, int yy) { return xx * yy / gcd(xx, yy); }
bool prime(int xx) {
  if (xx <= 1) {
    return 0;
  }
  for (int i = 2; i * i <= xx; i++) {
    if (xx % i == 0) {
      return 0;
    }
  }
  return 1;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int h, w, cx, cy, dx, dy, c = 0;
  queue<P> que;
  cin >> h >> w >> cy >> cx >> dy >> dx;
  cx--;
  cy--;
  dx--;
  dy--;
  vector<vector<char>> vec(h, vector<char>(w, 'x'));
  rep(i, h){rep(j, w){cin >> vec[i][j];
}
}
{
  queue<P> que2;
  vector<P> vec2;
  que2.push(m_p(cy, cx));
  while (!que2.empty()) {
    int fi = que2.front().first, se = que2.front().second;
    que2.pop();
    if (fi == dy && se == dx) {
      cout << 0 << endl;
      return 0;
    }
    vec2.push_back(m_p(fi, se));
    vec[fi][se] = 'o';
    if (fi > 0 && vec[fi - 1][se] == '.') {
      vec[fi - 1][se] = 'o';
      que2.push(m_p(fi - 1, se));
    }
    if (fi < h - 1 && vec[fi + 1][se] == '.') {
      vec[fi + 1][se] = 'o';
      que2.push(m_p(fi + 1, se));
    }
    if (se > 0 && vec[fi][se - 1] == '.') {
      vec[fi][se - 1] = 'o';
      que2.push(m_p(fi, se - 1));
    }
    if (se < w - 1 && vec[fi][se + 1] == '.') {
      vec[fi][se + 1] = 'o';
      que2.push(m_p(fi, se + 1));
    }
  }
  for (P p : vec2) {
    for (int i = p.first - 2; i < p.first + 3; i++) {
      if (i < 0 || i >= h)
        continue;
      for (int j = p.second - 2; j < p.second + 3; j++) {
        if (j < 0 || j >= w)
          continue;
        if (vec[i][j] == '.') {
          que.push(m_p(i, j));
        }
      }
    }
  }
}
/*
rep(i, h) {
        rep(j, w) {
                cout << vec[i][j];
        }
        cout << endl;
}
*/
while (1) {
  c++;
  if (que.empty()) {
    cout << -1 << endl;
    return 0;
  }
  vector<P> vec2;
  while (!que.empty()) {
    int fi = que.front().first, se = que.front().second;
    que.pop();
    if (fi == dy && se == dx) {
      cout << c << endl;
      return 0;
    }
    vec2.push_back(m_p(fi, se));
    vec[fi][se] = 'o';
    if (fi > 0 && vec[fi - 1][se] == '.') {
      vec[fi - 1][se] = 'o';
      que.push(m_p(fi - 1, se));
    }
    if (fi < h - 1 && vec[fi + 1][se] == '.') {
      vec[fi + 1][se] = 'o';
      que.push(m_p(fi + 1, se));
    }
    if (se > 0 && vec[fi][se - 1] == '.') {
      vec[fi][se - 1] = 'o';
      que.push(m_p(fi, se - 1));
    }
    if (se < w - 1 && vec[fi][se + 1] == '.') {
      vec[fi][se + 1] = 'o';
      que.push(m_p(fi, se + 1));
    }
  }
  for (P p : vec2) {
    for (int i = p.first - 2; i < p.first + 3; i++) {
      if (i < 0 || i >= h)
        continue;
      for (int j = p.second - 2; j < p.second + 3; j++) {
        if (j < 0 || j >= w)
          continue;
        if (vec[i][j] == '.') {
          que.push(m_p(i, j));
        }
      }
    }
  }
}
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <ctime>
#include <deque>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <stdlib.h>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#pragma GCC target("avx2") // AtCoderでは "avx" にする
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#define int long long
#define endl "\\n"
#define all(v) v.begin(), v.end()
#define fir first
#define sec second
#define m_p make_pair
#define m_t make_tuple
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef pair<int, int> P;
typedef long double ld;
typedef long long ll;
template <class T> using PQ_inv = priority_queue<T, vector<T>, greater<T>>;

const double pai = 3.1415926535897;
const ll mod = 1000000007;
const int INF = 1000000021;
const ll LINF = 2000000000000000000;
const int MAX = 510000;
const ll MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
// n個を1個以上のx組のグループに分ける重複組み合わせはcom(n-1,x-1)
long long COM(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll PER(int n, int k) {
  if (n < 0 || k < 0)
    return 0;
  if (n < k)
    return fac[n];
  return fac[n] * finv[n - k] % mod;
}

long long modinv(long long a, long long m) {
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
long long modpow(int a, int n) {
  int res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

struct edge {
  int to, cost;
};
edge m_e(int xx, int yy) {
  edge ed;
  ed.to = xx;
  ed.cost = yy;
  return ed;
}
// x未満の要素数を返す二分探索関数
int b_s(vector<int> &vec, int xx) {
  return lower_bound(all(vec), xx) - vec.begin();
}
template <class T> void vecout(vector<T> &vec) {
  for (T t : vec)
    cout << t << " ";
  cout << endl;
}
template <class T> void vecin(vector<T> &vec) {
  for (int i = 0; i < vec.size(); i++)
    cin >> vec[i];
}
bool chmax(int &xx, int yy) {
  if (xx < yy) {
    xx = yy;
    return true;
  }
  return false;
}
bool chmin(int &xx, int yy) {
  if (xx > yy) {
    xx = yy;
    return true;
  }
  return false;
}
double dist(int x, int y) { return sqrt(x * x + y * y); }
double dist(int xx1, int xx2, int yy1, int yy2) {
  return sqrt(abs(xx1 - xx2) * abs(xx1 - xx2) +
              abs(yy1 - yy2) * abs(yy1 - yy2));
}
ll mypow(int nn, int kk) {
  ll xx = 1;
  rep(i, kk) { xx *= nn; }
  return xx;
}
int gcd(int xx, int yy) {
  int p = xx;
  int q = yy;
  if (q > p)
    swap(p, q);
  while (p % q != 0) {
    p %= q;
    swap(p, q);
  }
  return q;
}
int lcm(int xx, int yy) { return xx * yy / gcd(xx, yy); }
bool prime(int xx) {
  if (xx <= 1) {
    return 0;
  }
  for (int i = 2; i * i <= xx; i++) {
    if (xx % i == 0) {
      return 0;
    }
  }
  return 1;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int h, w, cx, cy, dx, dy, c = 0;
  cin >> h >> w >> cy >> cx >> dy >> dx;
  cx--;
  cy--;
  dx--;
  dy--;
  vector<vector<char>> vec(h, vector<char>(w, 'x'));
  rep(i, h){rep(j, w){cin >> vec[i][j];
}
}
{
  queue<P> que;
  que.push(m_p(cy, cx));
  while (!que.empty()) {
    int fi = que.front().first, se = que.front().second;
    que.pop();
    if (fi == dy && se == dx) {
      cout << 0 << endl;
      return 0;
    }
    vec[fi][se] = 'o';
    if (fi > 0 && vec[fi - 1][se] == '.') {
      vec[fi - 1][se] = 'o';
      que.push(m_p(fi - 1, se));
    }
    if (fi < h - 1 && vec[fi + 1][se] == '.') {
      vec[fi + 1][se] = 'o';
      que.push(m_p(fi + 1, se));
    }
    if (se > 0 && vec[fi][se - 1] == '.') {
      vec[fi][se - 1] = 'o';
      que.push(m_p(fi, se - 1));
    }
    if (se < w - 1 && vec[fi][se + 1] == '.') {
      vec[fi][se + 1] = 'o';
      que.push(m_p(fi, se + 1));
    }
  }
}
/*
rep(i, h) {
        rep(j, w) {
                cout << vec[i][j];
        }
        cout << endl;
}
*/
while (1) {
  c++;
  queue<P> que;
  rep(i, h) {
    rep(j, w) {
      if (vec[i][j] != '.')
        continue;
      for (int k = i - 2; k < i + 3; k++) {
        if (k < 0 || k >= h)
          continue;
        for (int l = j - 2; l < j + 3; l++) {
          if (l < 0 || l >= w)
            continue;
          if (vec[k][l] == 'o') {
            que.push(m_p(i, j));
          }
        }
      }
    }
  }
  if (que.empty()) {
    cout << -1 << endl;
    return 0;
  }
  while (!que.empty()) {
    int fi = que.front().first, se = que.front().second;
    que.pop();
    if (fi == dy && se == dx) {
      cout << c << endl;
      return 0;
    }
    vec[fi][se] = 'o';
    if (fi > 0 && vec[fi - 1][se] == '.') {
      vec[fi - 1][se] = 'o';
      que.push(m_p(fi - 1, se));
    }
    if (fi < h - 1 && vec[fi + 1][se] == '.') {
      vec[fi + 1][se] = 'o';
      que.push(m_p(fi + 1, se));
    }
    if (se > 0 && vec[fi][se - 1] == '.') {
      vec[fi][se - 1] = 'o';
      que.push(m_p(fi, se - 1));
    }
    if (se < w - 1 && vec[fi][se + 1] == '.') {
      vec[fi][se + 1] = 'o';
      que.push(m_p(fi, se + 1));
    }
  }
}
}