Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

// Define
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T> using pvector = vector<pair<T, T>>;
template <class T>
using rpriority_queue = priority_queue<T, vector<T>, greater<T>>;
constexpr const ll dx[4] = {1, 0, -1, 0};
constexpr const ll dy[4] = {0, 1, 0, -1};
constexpr const ll MOD = 1e9 + 7;
constexpr const ll mod = 998244353;
constexpr const ll INF = 1LL << 60;
constexpr const ll inf = 1 << 30;
constexpr const char rt = '\n';
constexpr const char sp = ' ';
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define elif else if
#define all(a, v, ...)                                                         \
  ([&](decltype((v)) w) { return (a)(begin(w), end(w), ##__VA_ARGS__); })(v)
#define rall(a, v, ...)                                                        \
  ([&](decltype((v)) w) { return (a)(rbegin(w), rend(w), ##__VA_ARGS__); })(v)
#define fi first
#define se second

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 (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

// Debug
#define debug(...)                                                             \
  {                                                                            \
    cerr << __LINE__ << ": " << #__VA_ARGS__ << " = ";                         \
    for (auto &&X : {__VA_ARGS__})                                             \
      cerr << "[" << X << "] ";                                                \
    cerr << rt;                                                                \
  }

#define dump(a, h, w)                                                          \
  {                                                                            \
    cerr << __LINE__ << ": " << #a << " = [" << rt;                            \
    rep(_i, h) {                                                               \
      rep(_j, w) {                                                             \
        if (a[_i][_j] <= -INF / 2)                                             \
          cerr << '-';                                                         \
        if (abs(a[_i][_j]) >= INF / 2)                                         \
          cerr << "∞" << sp;                                                   \
        else                                                                   \
          cerr << a[_i][_j] << sp;                                             \
      }                                                                        \
      cerr << rt;                                                              \
    }                                                                          \
    cerr << "]" << rt;                                                         \
  }

#define vdump(a, n)                                                            \
  {                                                                            \
    cerr << __LINE__ << ": " << #a << " = [";                                  \
    rep(_i, n) {                                                               \
      if (_i)                                                                  \
        cerr << sp;                                                            \
      if (a[_i] <= -INF / 2)                                                   \
        cerr << '-';                                                           \
      if (abs(a[_i]) >= INF / 2)                                               \
        cerr << "∞" << sp;                                                     \
      else                                                                     \
        cerr << a[_i];                                                         \
    }                                                                          \
    cerr << "]" << rt;                                                         \
  }

// Loop
#define inc(i, a, n) for (ll i = (a), _##i = (n); i <= _##i; ++i)
#define dec(i, a, n) for (ll i = (a), _##i = (n); i >= _##i; --i)
#define rep(i, n) for (ll i = 0, _##i = (n); i < _##i; ++i)
#define each(i, a) for (auto &&i : a)

// Stream
#define fout(n) cout << fixed << setprecision(n)
struct io {
  io() { cin.tie(nullptr), ios::sync_with_stdio(false); }
} io;

// Speed
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// Math
inline constexpr ll gcd(const ll a, const ll b) {
  return b ? gcd(b, a % b) : a;
}
inline constexpr ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }

inline constexpr ll modulo(const ll n, const ll m = MOD) {
  ll k = n % m;
  return k + m * (k < 0);
}
inline constexpr ll chmod(ll &n, const ll m = MOD) {
  n %= m;
  return n += m * (n < 0);
}
inline constexpr ll mpow(ll a, ll n, const ll m = MOD) {
  ll r = 1;
  rep(i, 64) {
    if (n & (1LL << i))
      r *= a;
    chmod(r, m);
    a *= a;
    chmod(a, m);
  }
  return r;
}
inline ll inv(const ll n, const ll m = MOD) {
  ll a = n, b = m, x = 1, y = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    x -= t * y;
    swap(x, y);
  }
  return modulo(x, m);
}

signed main() {
  ll H, W, K;
  cin >> H >> W >> K;

  ll A, B, C, D2;
  cin >> A >> B >> C >> D2;
  A--, B--, C--, D2--;

  string S[H];
  rep(i, H) cin >> S[i];

  ll D[H][W];
  rep(i, H) rep(j, W) D[i][j] = INF;

  using P = pair<ll, ll>;
  queue<P> Q;
  D[A][B] = 0;
  Q.push(mp(A, B));

  while (Q.size()) {
    ll i, j;
    tie(i, j) = Q.front();
    Q.pop();
    rep(k, 4) {
      inc(l, 1, K) {
        ll x = i + dx[k] * l, y = j + dy[k] * l;
        debug(i, j, x, y);
        if (not(0 <= x and x < H))
          break;
        if (not(0 <= y and y < W))
          break;
        if (S[x][y] != '.')
          break;
        if (D[x][y] <= D[i][j])
          break;

        if (D[x][y] > D[i][j] + 1) {
          Q.push(mp(x, y));
          D[x][y] = D[i][j] + 1;
        }
      }
    }
  }
  S[A][B] = 'S';
  S[C][D2] = 'G';

  if (D[C][D2] >= INF) {
    cout << -1 << rt;
  } else {
    cout << D[C][D2] << rt;
  }
}

// -g -D_GLIBCXX_DEBUG -fsanitize=undefined


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

// Define
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T> using pvector = vector<pair<T, T>>;
template <class T>
using rpriority_queue = priority_queue<T, vector<T>, greater<T>>;
constexpr const ll dx[4] = {1, 0, -1, 0};
constexpr const ll dy[4] = {0, 1, 0, -1};
constexpr const ll MOD = 1e9 + 7;
constexpr const ll mod = 998244353;
constexpr const ll INF = 1LL << 60;
constexpr const ll inf = 1 << 30;
constexpr const char rt = '\n';
constexpr const char sp = ' ';
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define elif else if
#define all(a, v, ...)                                                         \
  ([&](decltype((v)) w) { return (a)(begin(w), end(w), ##__VA_ARGS__); })(v)
#define rall(a, v, ...)                                                        \
  ([&](decltype((v)) w) { return (a)(rbegin(w), rend(w), ##__VA_ARGS__); })(v)
#define fi first
#define se second

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 (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

// Debug
#define debug(...)                                                             \
  {                                                                            \
    cerr << __LINE__ << ": " << #__VA_ARGS__ << " = ";                         \
    for (auto &&X : {__VA_ARGS__})                                             \
      cerr << "[" << X << "] ";                                                \
    cerr << rt;                                                                \
  }

#define dump(a, h, w)                                                          \
  {                                                                            \
    cerr << __LINE__ << ": " << #a << " = [" << rt;                            \
    rep(_i, h) {                                                               \
      rep(_j, w) {                                                             \
        if (a[_i][_j] <= -INF / 2)                                             \
          cerr << '-';                                                         \
        if (abs(a[_i][_j]) >= INF / 2)                                         \
          cerr << "∞" << sp;                                                   \
        else                                                                   \
          cerr << a[_i][_j] << sp;                                             \
      }                                                                        \
      cerr << rt;                                                              \
    }                                                                          \
    cerr << "]" << rt;                                                         \
  }

#define vdump(a, n)                                                            \
  {                                                                            \
    cerr << __LINE__ << ": " << #a << " = [";                                  \
    rep(_i, n) {                                                               \
      if (_i)                                                                  \
        cerr << sp;                                                            \
      if (a[_i] <= -INF / 2)                                                   \
        cerr << '-';                                                           \
      if (abs(a[_i]) >= INF / 2)                                               \
        cerr << "∞" << sp;                                                     \
      else                                                                     \
        cerr << a[_i];                                                         \
    }                                                                          \
    cerr << "]" << rt;                                                         \
  }

// Loop
#define inc(i, a, n) for (ll i = (a), _##i = (n); i <= _##i; ++i)
#define dec(i, a, n) for (ll i = (a), _##i = (n); i >= _##i; --i)
#define rep(i, n) for (ll i = 0, _##i = (n); i < _##i; ++i)
#define each(i, a) for (auto &&i : a)

// Stream
#define fout(n) cout << fixed << setprecision(n)
struct io {
  io() { cin.tie(nullptr), ios::sync_with_stdio(false); }
} io;

// Speed
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// Math
inline constexpr ll gcd(const ll a, const ll b) {
  return b ? gcd(b, a % b) : a;
}
inline constexpr ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }

inline constexpr ll modulo(const ll n, const ll m = MOD) {
  ll k = n % m;
  return k + m * (k < 0);
}
inline constexpr ll chmod(ll &n, const ll m = MOD) {
  n %= m;
  return n += m * (n < 0);
}
inline constexpr ll mpow(ll a, ll n, const ll m = MOD) {
  ll r = 1;
  rep(i, 64) {
    if (n & (1LL << i))
      r *= a;
    chmod(r, m);
    a *= a;
    chmod(a, m);
  }
  return r;
}
inline ll inv(const ll n, const ll m = MOD) {
  ll a = n, b = m, x = 1, y = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    x -= t * y;
    swap(x, y);
  }
  return modulo(x, m);
}

signed main() {
  ll H, W, K;
  cin >> H >> W >> K;

  ll A, B, C, D2;
  cin >> A >> B >> C >> D2;
  A--, B--, C--, D2--;

  string S[H];
  rep(i, H) cin >> S[i];

  ll D[H][W];
  rep(i, H) rep(j, W) D[i][j] = INF;

  using P = pair<ll, ll>;
  queue<P> Q;
  D[A][B] = 0;
  Q.push(mp(A, B));

  while (Q.size()) {
    ll i, j;
    tie(i, j) = Q.front();
    Q.pop();
    rep(k, 4) {
      inc(l, 1, K) {
        ll x = i + dx[k] * l, y = j + dy[k] * l;
        if (not(0 <= x and x < H))
          break;
        if (not(0 <= y and y < W))
          break;
        if (S[x][y] != '.')
          break;
        if (D[x][y] <= D[i][j])
          break;

        if (D[x][y] > D[i][j] + 1) {
          Q.push(mp(x, y));
          D[x][y] = D[i][j] + 1;
        }
      }
    }
  }
  S[A][B] = 'S';
  S[C][D2] = 'G';

  if (D[C][D2] >= INF) {
    cout << -1 << rt;
  } else {
    cout << D[C][D2] << rt;
  }
}

// -g -D_GLIBCXX_DEBUG -fsanitize=undefined