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

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const ll dx[9] = {0, -1, 0, 1, 1, -1, 1, -1, 0};
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;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, k;
  cin >> h >> w >> k;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--;
  gy--;
  sx--;
  gx--;
  vector<string> g(h);
  rep(i, h) { cin >> g[i]; }
  queue<pair<int, int>> que;
  que.push({sy, sx});
  vector<vector<int>> dist(h, vector<int>(w, inf));
  dist[sy][sx] = 0;
  while (!que.empty()) {
    pair<int, int> vv = que.front();
    que.pop();
    rep(i, 4) {
      pair<int, int> v = vv;
      int cnt = 0;
      while (cnt < k) {
        v.fi += dy[i];
        v.se += dx[i];
        if (v.fi < 0 || v.se < 0 || v.fi >= h || v.se >= w)
          break;
        if (g[v.fi][v.se] == '@')
          break;
        if (dist[v.fi][v.se] >= dist[vv.fi][vv.se] + 1) {
          if (chmin(dist[v.fi][v.se], dist[vv.fi][vv.se] + 1)) {
            que.push({v.fi, v.se});
          }
        } else
          break;
        cnt++;
      }
    }
  }
  if (dist[gy][gx] != inf)
    cout << dist[gy][gx] << endl;
  else
    cout << -1 << endl;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const ll dx[9] = {0, -1, 0, 1, 1, -1, 1, -1, 0};
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;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, k;
  cin >> h >> w >> k;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--;
  gy--;
  sx--;
  gx--;
  vector<string> g(h);
  rep(i, h) { cin >> g[i]; }
  queue<pair<int, int>> que;
  que.push({sy, sx});
  vector<vector<int>> dist(h, vector<int>(w, inf));
  dist[sy][sx] = 0;
  while (!que.empty()) {
    pair<int, int> vv = que.front();
    que.pop();
    rep(i, 4) {
      pair<int, int> v = vv;
      int cnt = 0;
      while (cnt < k) {
        v.fi += dy[i];
        v.se += dx[i];
        if (v.fi < 0 || v.se < 0 || v.fi >= h || v.se >= w)
          break;
        if (dist[v.fi][v.se] < dist[vv.fi][vv.se] + 1)
          break;
        if (g[v.fi][v.se] == '@')
          break;
        cnt++;
        dist[v.fi][v.se] = dist[vv.fi][vv.se] + 1;
        que.push({v.fi, v.se});
      }
    }
  }
  if (dist[gy][gx] != inf)
    cout << dist[gy][gx] << endl;
  else
    cout << -1 << endl;
}