Problem p02644 (C++) — buggy submission, verdict: Time Limit Exceeded

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

#define forn(i, x, n) for (int i = x; i < n; i++)
#define ff first
#define ss second
#define int long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define mii map<int, int>
#define pqb priority_queue<int>
#define pqs priority_queue<int, vi, greater<int>>
#define setbits(x) __builtin_popcountll(x)
#define zrobits(x) __builtin_ctzll(x)
#define mod 1000000007
#define inf 1e18
#define ps(x, y) fixed << setprecision(y) << x
#define mk(arr, n, type) type *arr = new type[n];
#define w(x)                                                                   \\
  int x;                                                                       \\
  cin >> x;                                                                    \\
  while (x--)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void zeus() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
}
int h, w, k;
vector<pii> dir = {{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
bool isin(int i, int j) { return (i > 0 && j > 0 && i <= h && j <= w); }
void bfs(int x1, int y1, int x2, int y2, vector<vector<char>> pond,
         vector<vi> &visited, vector<vi> &dist) {

  visited[x1][y1] = 1;
  dist[x1][y1] = 0;
  queue<pii> q;
  q.push({x1, y1});

  while (!q.empty()) {
    pii x = q.front();
    q.pop();
    // cout << x.ff << " " << x.ss << endl;

    forn(i, 0, 4) {

      forn(j, 1, k + 1) {
        int i1 = x.ff + j * dir[i].ff;
        int j1 = x.ss + j * dir[i].ss;

        if (!isin(i1, j1)) {
          break;
        }
        if (pond[i1][j1] == '@') {
          break;
        }
        if (visited[i1][j1] && dist[i1][j1] < 1 + dist[x.ff][x.ss]) {
          break;
        }
        if (!visited[i1][j1]) {
          visited[i1][j1] = 1;
          dist[i1][j1] = 1 + dist[x.ff][x.ss];
          q.push({i1, j1});
          // cout << i1 << " " << j1 << endl;
        }
        if (i1 == x2 && j1 == y2) {
          return;
        }
      }
    }
  }
}
int32_t main() {
  zeus();
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  vector<vector<char>> pond(h + 1, vector<char>(w + 1));
  vector<vector<int>> visited(h + 1, vector<int>(w + 1));
  vector<vector<int>> dist(h + 1, vector<int>(w + 1));

  forn(i, 1, h + 1) {
    forn(j, 1, w + 1) { cin >> pond[i][j]; }
  }

  if (pond[x1][y1] == '@' || pond[x2][y2] == '@') {
    cout << -1 << endl;
    return 0;
  }
  bfs(x1, y1, x2, y2, pond, visited, dist);

  if (visited[x2][y2] == 0) {
    cout << -1 << endl;
  } else {
    cout << dist[x2][y2] << endl;
  }
}

Error: TLE

Fixed submission:

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

#define forn(i, x, n) for (int i = x; i < n; i++)
#define ff first
#define ss second
#define int long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define vi vector<int>
#define mii map<int, int>
#define pqb priority_queue<int>
#define pqs priority_queue<int, vi, greater<int>>
#define setbits(x) __builtin_popcountll(x)
#define zrobits(x) __builtin_ctzll(x)
#define mod 1000000007
#define inf 1e18
#define ps(x, y) fixed << setprecision(y) << x
#define mk(arr, n, type) type *arr = new type[n];
#define w(x)                                                                   \\
  int x;                                                                       \\
  cin >> x;                                                                    \\
  while (x--)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void zeus() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
}
int h, w, k;
vector<pii> dir = {{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
bool isin(int i, int j) { return (i > 0 && j > 0 && i <= h && j <= w); }
void bfs(int x1, int y1, int x2, int y2, vector<vector<char>> pond,
         vector<vi> &visited, vector<vi> &dist) {

  visited[x1][y1] = 1;
  dist[x1][y1] = 0;
  queue<pii> q;
  q.push({x1, y1});

  while (!q.empty()) {
    pii x = q.front();
    q.pop();
    // cout << x.ff << " " << x.ss << endl;

    forn(i, 0, 4) {

      forn(j, 1, k + 1) {
        int i1 = x.ff + j * dir[i].ff;
        int j1 = x.ss + j * dir[i].ss;

        if (!isin(i1, j1)) {
          break;
        }
        if (pond[i1][j1] == '@') {
          break;
        }
        if (!visited[i1][j1]) {
          visited[i1][j1] = 1;
          dist[i1][j1] = 1 + dist[x.ff][x.ss];
          q.push({i1, j1});
          // cout << i1 << " " << j1 << endl;
        }
        if (i1 == x2 && j1 == y2) {
          return;
        }
      }
    }
  }
}
int32_t main() {
  zeus();
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  vector<vector<char>> pond(h + 1, vector<char>(w + 1));
  vector<vector<int>> visited(h + 1, vector<int>(w + 1));
  vector<vector<int>> dist(h + 1, vector<int>(w + 1));

  forn(i, 1, h + 1) {
    forn(j, 1, w + 1) { cin >> pond[i][j]; }
  }

  if (pond[x1][y1] == '@' || pond[x2][y2] == '@') {
    cout << -1 << endl;
    return 0;
  }
  bfs(x1, y1, x2, y2, pond, visited, dist);

  if (visited[x2][y2] == 0) {
    cout << -1 << endl;
  } else {
    cout << dist[x2][y2] << endl;
  }
}