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

#include <bits/stdc++.h>

using namespace std;

#define endl "\\n"
#define JAM(x) cout << #x << " = " << x << "\\n"
#define II()                                                                   \\
  ({                                                                           \\
    int a;                                                                     \\
    read(a);                                                                   \\
    a;                                                                         \\
  })
#define LL()                                                                   \\
  ({                                                                           \\
    ll a;                                                                      \\
    read(a);                                                                   \\
    a;                                                                         \\
  })
#define DD()                                                                   \\
  ({                                                                           \\
    double a;                                                                  \\
    scanf("%lf", &a);                                                          \\
    a;                                                                         \\
  })

// Fast Reader
template <class T> inline bool read(T &x) {
  int c = getchar();
  int sgn = 1;
  while (~c && c < '0' || c > '9') {
    if (c == '-')
      sgn = -1;
    c = getchar();
  }
  for (x = 0; ~c && '0' <= c && c <= '9'; c = getchar())
    x = x * 10 + c - '0';
  x *= sgn;
  return ~c;
}

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef pair<int, int> PII;
typedef vector<PII> VPI;

const int INF = 2e9;
const int MX = 100005;
const int MOD = 1000000007;
const double PI = acos(-1.0);

vector<int> sieve(100001);

long long int power(long long int a, long long int b) {
  a %= MOD;
  long long int res = 1;
  while (b > 0) {
    if (b & 1)
      res = res * a % MOD;
    a = a * a % MOD;
    b >>= 1;
  }
  return res;
}
bool isprime(int n) {
  if (n == 1)
    return 0;
  int i;
  for (i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}

void SIEVE() {
  int i, j;
  for (i = 0; i <= 100000; i++)
    sieve[i] = i;
  for (i = 2; i * i <= 100000; i++) {
    if (sieve[i] != i)
      continue;
    for (j = i * i; j <= 100000; j = j + i) {
      if (sieve[j] == j)
        sieve[j] = i;
    }
  }
}

/*_______________________________________________*/
int n, m;
int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, -1, 1};
bool isvalid(int x, int y) {
  if (x < 0 || x >= n || y < 0 || y >= m)
    return false;
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m;
  vector<vector<int>> times(n, vector<int>(m, INT_MAX));
  vector<vector<char>> grid(n, vector<char>(m));
  int i, j;
  int sx, sy, ex, ey;
  cin >> sx >> sy;
  cin >> ex >> ey;
  for (i = 0; i < n; i++) {
    for (j = 0; j < m; j++)
      cin >> grid[i][j];
  }
  deque<pair<int, int>> q;
  q.push_back({sx - 1, sy - 1});
  times[sx - 1][sy - 1] = 0;
  while (!q.empty()) {
    pair<int, int> cur = q.front();
    q.pop_front();
    if (times[ex - 1][ey - 1] == 0)
      break;
    for (i = 0; i < 4; i++) {
      int x = cur.first + dx[i];
      int y = cur.second + dy[i];
      if (isvalid(x, y) && times[x][y] > times[cur.first][cur.second] &&
          grid[x][y] == '.') {
        times[x][y] = times[cur.first][cur.second];
        q.push_front({x, y});
      }
    }
    for (i = -2; i <= 2; i++) {
      for (j = -2; j <= 2; j++) {
        int x = cur.first + i;
        int y = cur.second + j;
        if (isvalid(x, y) && times[x][y] > (times[cur.first][cur.second] + 1) &&
            grid[x][y] == '.') {
          times[x][y] = times[cur.first][cur.second] + 1;
          q.push_back({x, y});
        }
      }
    }
  }
  if (times[ex - 1][ey - 1] != INT_MAX)
    cout << times[ex - 1][ey - 1];
  else {
    cout << "-1";
  }
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

#define endl "\\n"
#define JAM(x) cout << #x << " = " << x << "\\n"
#define II()                                                                   \\
  ({                                                                           \\
    int a;                                                                     \\
    read(a);                                                                   \\
    a;                                                                         \\
  })
#define LL()                                                                   \\
  ({                                                                           \\
    ll a;                                                                      \\
    read(a);                                                                   \\
    a;                                                                         \\
  })
#define DD()                                                                   \\
  ({                                                                           \\
    double a;                                                                  \\
    scanf("%lf", &a);                                                          \\
    a;                                                                         \\
  })

// Fast Reader
template <class T> inline bool read(T &x) {
  int c = getchar();
  int sgn = 1;
  while (~c && c < '0' || c > '9') {
    if (c == '-')
      sgn = -1;
    c = getchar();
  }
  for (x = 0; ~c && '0' <= c && c <= '9'; c = getchar())
    x = x * 10 + c - '0';
  x *= sgn;
  return ~c;
}

typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef pair<int, int> PII;
typedef vector<PII> VPI;

const int INF = 2e9;
const int MX = 100005;
const int MOD = 1000000007;
const double PI = acos(-1.0);

vector<int> sieve(100001);

long long int power(long long int a, long long int b) {
  a %= MOD;
  long long int res = 1;
  while (b > 0) {
    if (b & 1)
      res = res * a % MOD;
    a = a * a % MOD;
    b >>= 1;
  }
  return res;
}
bool isprime(int n) {
  if (n == 1)
    return 0;
  int i;
  for (i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}

void SIEVE() {
  int i, j;
  for (i = 0; i <= 100000; i++)
    sieve[i] = i;
  for (i = 2; i * i <= 100000; i++) {
    if (sieve[i] != i)
      continue;
    for (j = i * i; j <= 100000; j = j + i) {
      if (sieve[j] == j)
        sieve[j] = i;
    }
  }
}

/*_______________________________________________*/
int n, m;
int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, -1, 1};
bool isvalid(int x, int y) {
  if (x < 0 || x >= n || y < 0 || y >= m)
    return false;
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m;
  vector<vector<int>> times(n, vector<int>(m, INT_MAX));
  vector<vector<char>> grid(n, vector<char>(m));
  int i, j;
  int sx, sy, ex, ey;
  cin >> sx >> sy;
  cin >> ex >> ey;
  for (i = 0; i < n; i++) {
    for (j = 0; j < m; j++)
      cin >> grid[i][j];
  }
  deque<pair<int, int>> q;
  q.push_front({sx - 1, sy - 1});
  times[sx - 1][sy - 1] = 0;
  while (!q.empty()) {
    pair<int, int> cur = q.front();
    q.pop_front();
    if (times[ex - 1][ey - 1] == 0)
      break;
    for (i = 0; i < 4; i++) {
      int x = cur.first + dx[i];
      int y = cur.second + dy[i];
      if (isvalid(x, y) && times[x][y] > times[cur.first][cur.second] &&
          grid[x][y] == '.') {
        times[x][y] = times[cur.first][cur.second];
        q.push_back({x, y});
      }
    }
    for (i = -2; i <= 2; i++) {
      for (j = -2; j <= 2; j++) {
        int x = cur.first + i;
        int y = cur.second + j;
        if (isvalid(x, y) && times[x][y] > (times[cur.first][cur.second] + 1) &&
            grid[x][y] == '.') {
          times[x][y] = times[cur.first][cur.second] + 1;
          q.push_back({x, y});
        }
      }
    }
  }
  if (times[ex - 1][ey - 1] != INT_MAX)
    cout << times[ex - 1][ey - 1];
  else {
    cout << "-1";
  }
}