Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
#define get_unique(x) x.erase(unique(all(x)), x.end());
typedef long long ll;
typedef complex<double> Complex;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> vector<T> make_vec(size_t a) { return vector<T>(a); }
template <class T, class... Ts> auto make_vec(size_t a, Ts... ts) {
  return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T> ostream &operator<<(ostream &os, vector<T> v) {
  for (int i = 0; i < sz(v); i++) {
    os << v[i];
    if (i < sz(v) - 1)
      os << " ";
  }
  return os;
}
int main() {
  int h, w, k;
  cin >> h >> w >> k;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--, sx--, gy--, gx--;
  auto c = make_vec<bool>(h, w);
  rep(i, h) rep(j, w) {
    char cr;
    cin >> cr;
    c[i][j] = (cr == '.');
  }

  vector<int> dy = {0, 1, 0, -1};
  vector<int> dx = {1, 0, -1, 0};
  using P = pair<int, int>;
  queue<P> q;
  q.push(P(sy, sx));
  auto d = make_vec<int>(h, w);
  rep(i, h) rep(j, w) d[i][j] = INF;
  d[sy][sx] = 0;
  while (sz(q)) {
    auto [y, x] = q.front();
    q.pop();
    rep(dd, 4) {
      int ny = y + dy[dd], nx = x + dx[dd];
      while (0 <= ny && ny < h && 0 <= nx && nx < w && c[ny][nx] &&
             abs(ny - y) <= k && abs(nx - x) <= k && d[ny][nx] > d[y][x]) {
        q.push(P(ny, nx));
        chmin(d[ny][nx], d[y][x] + 1);
        if (P(ny, nx) == P(gy, gx)) {
          cout << d[ny][nx] << endl;
          return 0;
        }
        ny += dy[dd];
        nx += dx[dd];
      }
    }
  }
  cout << -1 << endl;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
#define get_unique(x) x.erase(unique(all(x)), x.end());
typedef long long ll;
typedef complex<double> Complex;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> vector<T> make_vec(size_t a) { return vector<T>(a); }
template <class T, class... Ts> auto make_vec(size_t a, Ts... ts) {
  return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T> ostream &operator<<(ostream &os, vector<T> v) {
  for (int i = 0; i < sz(v); i++) {
    os << v[i];
    if (i < sz(v) - 1)
      os << " ";
  }
  return os;
}
int main() {
  int h, w, k;
  cin >> h >> w >> k;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--, sx--, gy--, gx--;
  auto c = make_vec<bool>(h, w);
  rep(i, h) rep(j, w) {
    char cr;
    cin >> cr;
    c[i][j] = (cr == '.');
  }

  vector<int> dy = {0, 1, 0, -1};
  vector<int> dx = {1, 0, -1, 0};
  using P = pair<int, int>;
  queue<P> q;
  q.push(P(sy, sx));
  auto d = make_vec<int>(h, w);
  rep(i, h) rep(j, w) d[i][j] = INF;
  d[sy][sx] = 0;
  while (sz(q)) {
    auto [y, x] = q.front();
    q.pop();
    rep(dd, 4) {
      int ny = y + dy[dd], nx = x + dx[dd];
      while (0 <= ny && ny < h && 0 <= nx && nx < w && c[ny][nx] &&
             abs(ny - y) <= k && abs(nx - x) <= k && d[ny][nx] > d[y][x]) {
        if (d[ny][nx] == INF) {
          q.push(P(ny, nx));
          chmin(d[ny][nx], d[y][x] + 1);
        }
        if (P(ny, nx) == P(gy, gx)) {
          cout << d[ny][nx] << endl;
          return 0;
        }
        ny += dy[dd];
        nx += dx[dd];
      }
    }
  }
  cout << -1 << endl;
}