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

#include <bits/stdc++.h>
using namespace std;

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPr(i, n) for (int i = (n)-1; i >= 0; --i)
#define FORq(i, m, n) for (int i = (m); i <= (n); ++i)
#define FORqr(i, m, n) for (int i = (n); i >= (m); --i)
#define MP make_pair
#define SIN(x, S) (S.count(x) != 0)
#define M0(x) memset(x, 0, sizeof(x))
#define FILL(x, y) memset(x, y, sizeof(x))
#define MM(x) memset(x, -1, sizeof(x))
#define ALL(x) (x).begin(), (x).end()
#define DB(x) cerr << #x << " = " << x << endl
#define DB2(x, y)                                                              \\
  cerr << "(" << #x << ", " << #y << ") = (" << x << ", " << y << ")\\n";
#define DEBUG                                                                  \\
  int x12345;                                                                  \\
  cin >> x12345;
typedef pair<int, int> PII;
typedef pair<long long, long long> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef long long ll;
typedef long long integer;
const long long MOD = 1e9 + 7;
///////////////////////////////////////////////
// for template
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
///////////////////////////////////////////////
/// 🍈( '-' 🍈 |AC|
const ll M = 1e9;
const ll MAX = 1e16;
char grid[1002][1002];
bool visited[1002][1002];
ll cost[1002][1002];
int dx[4] = {0, 1, 0, -1};
int dy[4] = {1, 0, -1, 0};
int ddx[20] = {-2, -1, 0,  1,  2,  2,  2,  2,  2, 1,
               0,  -1, -2, -2, -2, -2, -1, -1, 1, 1};
int ddy[20] = {-2, -2, -2, -2, -2, -1, 0,  1, 2, 2,
               2,  2,  2,  1,  0,  -1, -1, 1, 1, -1};

int main() {
  int H, W;
  cin >> H >> W;
  int Ch, Cw, Dh, Dw;
  cin >> Ch >> Cw >> Dh >> Dw;
  REP(i, H) {
    REP(j, W) { cin >> grid[i][j]; }
  }
  Ch--;
  Cw--;
  Dh--;
  Dw--;
  REP(i, H) {
    REP(j, W) { cost[i][j] = MAX; }
  }
  cost[Ch][Cw] = 0;
  deque<PII> Q;
  Q.push_front(MP(Ch, Cw));
  while (!Q.empty()) {
    PII now = Q.front();
    Q.pop_front();
    visited[now.first][now.second] = true;
    REP(k, 4) {
      int newx = now.first + dx[k];
      int newy = now.second + dy[k];
      if (newx < 0)
        continue;
      if (newx >= H)
        continue;
      if (newy < 0)
        continue;
      if (newy >= W)
        continue;
      if (grid[newx][newy] == '#')
        continue;
      if (visited[newx][newy])
        continue;
      cost[newx][newy] = cost[now.first][now.second];
      Q.push_front(MP(newx, newy));
    }
    for (int ddx = -2; ddx <= 2; ddx++) {
      for (int ddy = -2; ddy <= 2; ddy++) {
        int newx = now.first + ddx;
        int newy = now.second + ddy;
        if (newx < 0)
          continue;
        if (newx >= H)
          continue;
        if (newy < 0)
          continue;
        if (newy >= W)
          continue;
        if (grid[newx][newy] == '#')
          continue;
        if (visited[newx][newy])
          continue;
        if (cost[newx][newy] <= cost[now.first][now.second] + 1)
          continue;
        cost[newx][newy] = cost[now.first][now.second] + 1;
        Q.push_back(MP(newx, newy));
      }
    }
  }

  if (cost[Dh][Dw] == MAX) {
    cout << -1 << endl;
  } else {
    cout << cost[Dh][Dw] << endl;
  }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPr(i, n) for (int i = (n)-1; i >= 0; --i)
#define FORq(i, m, n) for (int i = (m); i <= (n); ++i)
#define FORqr(i, m, n) for (int i = (n); i >= (m); --i)
#define MP make_pair
#define SIN(x, S) (S.count(x) != 0)
#define M0(x) memset(x, 0, sizeof(x))
#define FILL(x, y) memset(x, y, sizeof(x))
#define MM(x) memset(x, -1, sizeof(x))
#define ALL(x) (x).begin(), (x).end()
#define DB(x) cerr << #x << " = " << x << endl
#define DB2(x, y)                                                              \\
  cerr << "(" << #x << ", " << #y << ") = (" << x << ", " << y << ")\\n";
#define DEBUG                                                                  \\
  int x12345;                                                                  \\
  cin >> x12345;
typedef pair<int, int> PII;
typedef pair<long long, long long> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef long long ll;
typedef long long integer;
const long long MOD = 1e9 + 7;
///////////////////////////////////////////////
// for template
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
///////////////////////////////////////////////
/// 🍈( '-' 🍈 |AC|
const ll M = 1e9;
const ll MAX = 1e16;
char grid[1002][1002];
bool visited[1002][1002];
ll cost[1002][1002];
int dx[4] = {0, 1, 0, -1};
int dy[4] = {1, 0, -1, 0};
int ddx[20] = {-2, -1, 0,  1,  2,  2,  2,  2,  2, 1,
               0,  -1, -2, -2, -2, -2, -1, -1, 1, 1};
int ddy[20] = {-2, -2, -2, -2, -2, -1, 0,  1, 2, 2,
               2,  2,  2,  1,  0,  -1, -1, 1, 1, -1};

int main() {
  int H, W;
  cin >> H >> W;
  int Ch, Cw, Dh, Dw;
  cin >> Ch >> Cw >> Dh >> Dw;
  REP(i, H) {
    REP(j, W) { cin >> grid[i][j]; }
  }
  Ch--;
  Cw--;
  Dh--;
  Dw--;
  REP(i, H) {
    REP(j, W) { cost[i][j] = MAX; }
  }
  cost[Ch][Cw] = 0;
  queue<PII> Q;
  Q.push(MP(Ch, Cw));
  while (!Q.empty()) {
    PII now = Q.front();
    Q.pop();
    visited[now.first][now.second] = true;
    REP(k, 4) {
      int newx = now.first + dx[k];
      int newy = now.second + dy[k];
      if (newx < 0)
        continue;
      if (newx >= H)
        continue;
      if (newy < 0)
        continue;
      if (newy >= W)
        continue;
      if (grid[newx][newy] == '#')
        continue;
      if (visited[newx][newy])
        continue;
      ll ncost = cost[now.first][now.second] + 1;
      if (ncost < cost[newx][newy])
        cost[newx][newy] = ncost;
      Q.push(MP(newx, newy));
    }
    REP(k, 20) {
      int newx = now.first + ddx[k];
      int newy = now.second + ddy[k];
      if (newx < 0)
        continue;
      if (newx >= H)
        continue;
      if (newy < 0)
        continue;
      if (newy >= W)
        continue;
      if (grid[newx][newy] == '#')
        continue;
      if (visited[newx][newy])
        continue;
      ll ncost = cost[now.first][now.second] + M;
      if (ncost < cost[newx][newy])
        cost[newx][newy] = ncost;
      Q.push(MP(newx, newy));
    }
  }

  if (cost[Dh][Dw] == MAX) {
    cout << -1 << endl;
  } else {
    cout << cost[Dh][Dw] / M << endl;
  }
}