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

// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using namespace std::chrono;

#define ll long long
#define ull unsigned long long
#define FIO                                                                    \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define ff first
#define ss second
#define vt vector
#define vll vt<ll>
#define pll pair<ll, ll>
#define vpll vt<pll>
#define vvll vt<vll>
#define all(v) v.begin(), v.end()
#define FOR(i, n) for (ll i = 0; i < n; i++)
#define ffo(i, a, b) for (ll i = a; i <= b; i++)
#define rfo(i, a, b) for (ll i = a; i >= b; i--)
#define space cout << "\\n\\n";
#define endl "\\n"
#define pqmx priority_queue<ll>
#define pqmn priority_queue<ll, vll, greater<ll>>
#define fps(x, y) fixed << setprecision(y) << x
#define merg(a, b, c)                                                          \\
  set_union(a.begin(), a.end(), b.begin(), b.end(), inserter(c, c.begin()))
#define set_ar(arr, v) memset(arr, v, sizeof(arr))
#define go_t                                                                   \\
  int testcases;                                                               \\
  cin >> testcases;                                                            \\
  ffo(caseno, 1, testcases)

#define ctime auto start = high_resolution_clock::now()
#define etime auto stop = high_resolution_clock::now()
#define ptime                                                                  \\
  auto z1z = duration_cast<microseconds>(stop - start);                        \\
  cout << "Time elapsed : " << z1z.count() << " microseconds\\n"

#define dbg1(x) cout << #x << ": " << x << '\\n';
#define dbg2(x, y) cout << #x << ": " << x << " | " << #y << ": " << y << '\\n';
#define dbg3(x, y, z)                                                          \\
  cout << #x << ": " << x << " | " << #y << ": " << y << " | " << #z << ": "   \\
       << z << '\\n';
#define dbg4(a, b, c, d)                                                       \\
  cout << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": "   \\
       << c << " | " << #d << ": " << d << '\\n';
#define dbg5(a, b, c, d, e)                                                    \\
  cout << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": "   \\
       << c << " | " << #d << ": " << d << " | " << #e << ": " << e << '\\n';

const ll mod = 1e9 + 7;
const ll N = 6e4 + 6;
const ll maxN = 1e5 + 5;
const ll MAX_SIZE = 2e6 + 6;
const ll INF = 0x3f3f3f3f3f3f3f3fll;
const double PI = 3.14159265359;

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};
// up, right, down, left

ll powerM(ll x, ll y, ll M = mod) { // default argument
  ll v = 1;
  x = x % M;
  while (y > 0) {
    if (y & 1)
      v = (v * x) % M;
    y = y >> 1;
    x = (x * x) % M;
  }
  return v;
}

ll power(ll x, ll y) {
  ll v = 1;
  while (y > 0) {
    if (y & 1)
      v = v * x;
    y = y >> 1;
    x = x * x;
  }
  return v;
}

string a[1003];
ll val[1002][1002];
ll h, w;
ll ch, cw, dh, dw;
deque<pll> pq;

int main() {
#ifndef ONLINE_JUDGE
  freopen("in4.txt", "r", stdin);
  freopen("out1.txt", "w", stdout);
#endif
  FIO FOR(i, 1002) {
    FOR(j, 1002) { val[i][j] = INF; }
  }
  cin >> h >> w;
  cin >> ch >> cw >> dh >> dw;
  FOR(i, h) { cin >> a[i]; }
  --ch, --cw, --dh, --dw;
  val[ch][cw] = 0;
  pq.push_front({ch, cw});
  while (!pq.empty()) {
    auto tp = pq.front();
    pq.pop_front();
    ll x = tp.ff;
    ll y = tp.ss;
    for (int i = -2; i <= 2; i++) {
      for (int j = -2; j <= 2; j++) {
        int xx = x + i, yy = y + j;
        if (xx < 0 || yy < 0 || xx >= h || yy >= w || a[xx][yy] == '#')
          continue;
        if (i == 0 && j == 0)
          continue;
        int w = 1;
        if (abs(i) + abs(j) == 1)
          w = 0;
        // using 0-1 BFS
        if (val[x][y] + w < val[xx][yy]) {
          val[xx][yy] = val[x][y] + w;
          if (w == 0)
            pq.push_front({xx, yy});
          else
            pq.push_back({xx, yy});
        }
      }
    }
  }
  if (val[dh][dw] == INF) {
    val[dh][dw] = -1;
  }
  cout << val[dh][dw];
  return 0;
}


Error: TLE

Fixed submission:

// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using namespace std::chrono;

#define ll long long
#define ull unsigned long long
#define FIO                                                                    \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(NULL);
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define ff first
#define ss second
#define vt vector
#define vll vt<ll>
#define pll pair<ll, ll>
#define vpll vt<pll>
#define vvll vt<vll>
#define all(v) v.begin(), v.end()
#define FOR(i, n) for (ll i = 0; i < n; i++)
#define ffo(i, a, b) for (ll i = a; i <= b; i++)
#define rfo(i, a, b) for (ll i = a; i >= b; i--)
#define space cout << "\\n\\n";
#define endl "\\n"
#define pqmx priority_queue<ll>
#define pqmn priority_queue<ll, vll, greater<ll>>
#define fps(x, y) fixed << setprecision(y) << x
#define merg(a, b, c)                                                          \\
  set_union(a.begin(), a.end(), b.begin(), b.end(), inserter(c, c.begin()))
#define set_ar(arr, v) memset(arr, v, sizeof(arr))
#define go_t                                                                   \\
  int testcases;                                                               \\
  cin >> testcases;                                                            \\
  ffo(caseno, 1, testcases)

#define ctime auto start = high_resolution_clock::now()
#define etime auto stop = high_resolution_clock::now()
#define ptime                                                                  \\
  auto z1z = duration_cast<microseconds>(stop - start);                        \\
  cout << "Time elapsed : " << z1z.count() << " microseconds\\n"

#define dbg1(x) cout << #x << ": " << x << '\\n';
#define dbg2(x, y) cout << #x << ": " << x << " | " << #y << ": " << y << '\\n';
#define dbg3(x, y, z)                                                          \\
  cout << #x << ": " << x << " | " << #y << ": " << y << " | " << #z << ": "   \\
       << z << '\\n';
#define dbg4(a, b, c, d)                                                       \\
  cout << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": "   \\
       << c << " | " << #d << ": " << d << '\\n';
#define dbg5(a, b, c, d, e)                                                    \\
  cout << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": "   \\
       << c << " | " << #d << ": " << d << " | " << #e << ": " << e << '\\n';

const ll mod = 1e9 + 7;
const ll N = 6e4 + 6;
const ll maxN = 1e5 + 5;
const ll MAX_SIZE = 2e6 + 6;
const ll INF = 0x3f3f3f3f3f3f3f3fll;
const double PI = 3.14159265359;

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};
// up, right, down, left

ll powerM(ll x, ll y, ll M = mod) { // default argument
  ll v = 1;
  x = x % M;
  while (y > 0) {
    if (y & 1)
      v = (v * x) % M;
    y = y >> 1;
    x = (x * x) % M;
  }
  return v;
}

ll power(ll x, ll y) {
  ll v = 1;
  while (y > 0) {
    if (y & 1)
      v = v * x;
    y = y >> 1;
    x = x * x;
  }
  return v;
}

string a[1003];
ll vis[1002][1002];
ll vis2[1002][1002];
ll val[1002][1002];
ll h, w;
ll ch, cw, dh, dw;
deque<pll> pq;

int main() {
#ifndef ONLINE_JUDGE
  freopen("in4.txt", "r", stdin);
  freopen("out1.txt", "w", stdout);
#endif
  FIO FOR(i, 1002) {
    FOR(j, 1002) { val[i][j] = INF; }
  }
  cin >> h >> w;
  cin >> ch >> cw >> dh >> dw;
  FOR(i, h) { cin >> a[i]; }
  --ch, --cw, --dh, --dw;
  val[ch][cw] = 0;
  vis[ch][cw] = 1;
  pq.push_front({ch, cw});
  while (!pq.empty()) {
    auto tp = pq.front();
    pq.pop_front();
    ll x = tp.ff;
    ll y = tp.ss;
    for (int i = -2; i <= 2; i++) {
      for (int j = -2; j <= 2; j++) {
        int xx = x + i, yy = y + j;
        if (xx < 0 || yy < 0 || xx >= h || yy >= w || vis[xx][yy] ||
            a[xx][yy] == '#')
          continue;
        if (i == 0 && j == 0)
          continue;
        if (abs(i) + abs(j) == 1) {
          val[xx][yy] = val[x][y] + 0;
          pq.push_front({xx, yy});
          vis[xx][yy] = 1;
        } else {
          val[xx][yy] = val[x][y] + 1;
          pq.push_back({xx, yy});
        }
      }
    }
  }
  if (val[dh][dw] == INF) {
    val[dh][dw] = -1;
  }
  cout << val[dh][dw];
  return 0;
}