Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
template <typename T> using Vec2 = vector<vector<T>>;
#define REP(i, m, n) for (ll i = (m); i < (n); ++i)
#define REPN(i, m, n) for (ll i = (m); i <= (n); ++i)
#define REPR(i, m, n) for (ll i = (m)-1; i >= (n); --i)
#define REPNR(i, m, n) for (ll i = (m); i >= (n); --i)
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define fs first
#define sc second
template <typename T> bool chmax(T &a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ll pow2(const T n) { return (1LL << n); }
template <typename T> void cosp(const T n) { cout << n << ' '; }
void co(void) { cout << '\n'; }
template <typename T> void co(const T n) { cout << n << '\n'; }
template <typename T1, typename T2> void co(pair<T1, T2> p) {
  cout << p.fs << ' ' << p.sc << '\n';
}
template <typename T> void co(const vector<T> &v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void co(initializer_list<T> v) {
  for (T i : v)
    cosp(i);
  co();
}
void ce(void) { cerr << '\n'; }
template <typename T> void ce(const T n) { cerr << n << '\n'; }
template <typename T> void cesp(const T n) { cerr << n << ' '; }
template <typename T> void ce(initializer_list<T> v) {
  for (T i : v)
    cesp(i);
  ce();
}
void sonic() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
void setp(const ll n) { cout << fixed << setprecision(n); }
constexpr int INF = 1e9 + 1;
constexpr ll LINF = 1e18L + 1;
constexpr ll MOD = 1e9L + 7;
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-11;
const double PI = acos(-1);

ll h, w, k;
VecS board;
Vec2<ll> dist;
ll dx[4] = {1, -1, 0, 0};
ll dy[4] = {0, 0, 1, -1};

bool in_board(ll x, ll y) {
  return x >= 0 && x < h && y >= 0 && y < w && board[x][y] == '.';
}

void bfs(ll fx, ll fy) {
  dist[fx][fy] = 0;
  queue<P> que;
  que.push({fx, fy});
  while (!que.empty()) {
    P p = que.front();
    que.pop();
    // co(p);
    ll a = p.first, b = p.second;
    rep(i, 4) {
      ll x = a, y = b;
      repn(j, k) {
        x += dx[i], y += dy[i];
        // co({x, y});
        if (in_board(x, y)) {
          if (chmin(dist[x][y], dist[a][b] + 1)) {
            que.push({x, y});
          }
        } else
          break;
      }
    }
  }
}

int main(void) {
  cin >> h >> w >> k;
  dist.resize(h);
  rep(i, h) dist[i].resize(w, LINF);
  ll x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  --x1, --y1, --x2, --y2;
  board.resize(h);
  rep(i, h) cin >> board[i];

  bfs(x1, y1);

  ll ans = dist[x2][y2];
  /*
  rep(i, h){
          rep(j, w) cosp(dist[i][j]);
          co();
  }
  */
  if (ans == LINF)
    ans = -1;
  co(ans);

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
template <typename T> using Vec2 = vector<vector<T>>;
#define REP(i, m, n) for (ll i = (m); i < (n); ++i)
#define REPN(i, m, n) for (ll i = (m); i <= (n); ++i)
#define REPR(i, m, n) for (ll i = (m)-1; i >= (n); --i)
#define REPNR(i, m, n) for (ll i = (m); i >= (n); --i)
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define fs first
#define sc second
template <typename T> bool chmax(T &a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> ll pow2(const T n) { return (1LL << n); }
template <typename T> void cosp(const T n) { cout << n << ' '; }
void co(void) { cout << '\n'; }
template <typename T> void co(const T n) { cout << n << '\n'; }
template <typename T1, typename T2> void co(pair<T1, T2> p) {
  cout << p.fs << ' ' << p.sc << '\n';
}
template <typename T> void co(const vector<T> &v) {
  for (T i : v)
    cosp(i);
  co();
}
template <typename T> void co(initializer_list<T> v) {
  for (T i : v)
    cosp(i);
  co();
}
void ce(void) { cerr << '\n'; }
template <typename T> void ce(const T n) { cerr << n << '\n'; }
template <typename T> void cesp(const T n) { cerr << n << ' '; }
template <typename T> void ce(initializer_list<T> v) {
  for (T i : v)
    cesp(i);
  ce();
}
void sonic() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
void setp(const ll n) { cout << fixed << setprecision(n); }
constexpr int INF = 1e9 + 1;
constexpr ll LINF = 1e18L + 1;
constexpr ll MOD = 1e9L + 7;
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-11;
const double PI = acos(-1);

ll h, w, k;
VecS board;
Vec2<ll> dist;
ll dx[4] = {1, -1, 0, 0};
ll dy[4] = {0, 0, 1, -1};

bool in_board(ll x, ll y) {
  return x >= 0 && x < h && y >= 0 && y < w && board[x][y] == '.';
}

void bfs(ll fx, ll fy) {
  dist[fx][fy] = 0;
  queue<P> que;
  que.push({fx, fy});
  while (!que.empty()) {
    P p = que.front();
    que.pop();
    // co(p);
    ll a = p.first, b = p.second;
    rep(i, 4) {
      ll x = a, y = b;
      repn(j, k) {
        x += dx[i], y += dy[i];
        // co({x, y});
        if (in_board(x, y)) {
          if (chmin(dist[x][y], dist[a][b] + 1)) {
            que.push({x, y});
          } else if (dist[x][y] == dist[a][b] + 1) {
            continue;
          } else
            break;
        } else
          break;
      }
    }
  }
}

int main(void) {
  cin >> h >> w >> k;
  dist.resize(h);
  rep(i, h) dist[i].resize(w, LINF);
  ll x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  --x1, --y1, --x2, --y2;
  board.resize(h);
  rep(i, h) cin >> board[i];

  bfs(x1, y1);

  ll ans = dist[x2][y2];
  /*
  rep(i, h){
          rep(j, w) cosp(dist[i][j]);
          co();
  }
  */
  if (ans == LINF)
    ans = -1;
  co(ans);

  return 0;
}