Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma region header
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#define int long long
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define mp make_pair
#define mt make_tuple
#define rep1(i, n) for (decltype(+n) i = 0; i < (n); i++)
#define rrep1(i, n) for (auto i = n - 1; i > static_cast<decltype(i)>(-1); i--)
#define rep2(i, a, b) for (auto i = (a); i < (b); i++)
#define rrep2(i, a, b) for (auto i = b - 1; i >= a; i--)
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep(...) GET_MACRO(__VA_ARGS__, rrep2, rrep1)(__VA_ARGS__)
#define each(i, a) for (auto &&i : (a))
#define split_pair(f, s, p)                                                    \
  auto f = p.first;                                                            \
  auto s = p.second
using namespace std;

using ll = long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vd = vector<ld>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using pii = pair<int, int>;
using vp = vector<pii>;
using vvp = vector<vp>;
using vvvp = vector<vvp>;
using mii = map<int, int>;
using vm = vector<mii>;
using vvm = vector<vm>;
using vvvm = vector<vvm>;

const int INF = 1e18;
const int MOD = 1e9 + 7;
int mod(int a) { return (a % MOD + MOD) % MOD; }
int m_add(int a, int b) { return (a + b) % MOD; }
int m_add(int a, int b, int c) { return (a + b + c) % MOD; }
int m_sub(int a, int b) { return (a + MOD - b) % MOD; }
int m_mul(int a, int b) { return a * b % MOD; }
int m_mul(int a, int b, int c) { return a * b % MOD * c % MOD; }
int m_bipow(int x, int y) {
  if (y == 0)
    return 1;
  else if (y == 1)
    return x % MOD;
  else if (y % 2 == 0) {
    int z = m_bipow(x, (int)(y / 2));
    return m_mul(z, z);
  } else {
    int z = m_bipow(x, (int)(y / 2));
    return m_mul(z, z, x);
  }
}
int m_inv(int x) { return m_bipow(x, MOD - 2); }
int m_div(int a, int b) { return m_mul(a, m_inv(b)); }

template <class T> void SORT(T &a) { stable_sort(all(a)); }
template <class T> void RSORT(T &a) { stable_sort(rall(a)); }
template <class T> void rev(T &a) { reverse(rall(a)); }
template <class T> void uniq(T &a) { a.erase(unique(all(a)), end(a)); }
template <class T> auto min_of(T a) { return *min_element(all(a)); }
template <class T> auto max_of(T a) { return *max_element(all(a)); }
template <class T> int sum_of(T a) { return accumulate(all(a), 0ll); }
template <class T, class U> auto sum_of(T a, U init) {
  return accumulate(all(a), init);
}
template <class T, class U> int count_of(T a, U i) { return count(all(a), i); }
template <class T, class U> int lower_index(T a, U i) {
  return lower_bound(all(a), i) - begin(a);
} // use member func for set
template <class T, class U> int upper_index(T a, U i) {
  return upper_bound(all(a), i) - begin(a);
}
template <class T, class U> bool binary(T a, U i) {
  return binary_search(all(a), i);
}
template <class T, class U> bool exists(T a, U i) {
  return find(all(a), i) != end(a);
}
template <class T> int sz(T a) { return a.size(); };

template <class T> void COUT(T x) { cout << x << endl; }
template <class T, class U> void COUT(T x, U y) {
  cout << x << ' ' << y << endl;
}
template <class T, class U, class V> void COUT(T x, U y, V z) {
  cout << x << ' ' << y << ' ' << z << endl;
}
template <class T> void CSP(T x) { cout << x << ' '; }
template <class T> void CVEC(T v) {
  int c = v.size() - 1;
  for (size_t i = 0; i < c; i++)
    cout << v[i] << ' ';
  if (c > -1)
    cout << v[c];
  cout << endl;
}

template <class T> bool amin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool amax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <class T> vector<pair<T, int>> indexed_vector(vector<T> v) {
  int n = sz(v);
  vector<pair<T, int>> w(n);
  for (int i = 0; i < n; i++)
    w[i] = make_pair(v[i], i);
  return w;
}
template <class T, class S> vector<pair<T, S>> zip(vector<T> v, vector<S> w) {
  int n = min(sz(v), sz(w));
  vector<pair<T, S>> x(n);
  for (int i = 0; i < n; i++)
    x[i] = make_pair(v[i], w[i]);
  return x;
}
template <class T, class S>
pair<vector<T>, vector<S>> unzip(vector<pair<T, S>> v) {
  int n = sz(v);
  auto w = make_pair(vector<T>(n), vector<S>(n));
  for (int i = 0; i < n; i++) {
    w.first[i] = v[i].first;
    w.second[i] = v[i].second;
  }
  return w;
}

vs split(const string &s, string d) {
  vs elms;
  size_t offset = 0, d_size = d.size();
  while (true) {
    size_t next = s.find_first_of(d, offset);
    if (next == string::npos) {
      elms.push_back(s.substr(offset));
      return elms;
    }
    elms.push_back(s.substr(offset, next - offset));
    offset = next + d_size;
  }
}
vs split(const string &s, char d) { return split(s, string(1, d)); }
string join(const vs &v, const string d = "") {
  string s;
  if (!v.empty()) {
    s += v[0];
    for (size_t i = 1, c = v.size(); i < c; ++i) {
      if (!d.empty())
        s += d;
      s += v[i];
    }
  }
  return s;
}
string join(const vs &v, const char d) { return join(v, string(1, d)); }
string pad_left(string s, int width, char filler = '0') {
  int n = sz(s);
  if (n > width)
    return s.substr(n - width);
  return string(width - n, filler) + s;
}

int ceil_div(int x, int y) { return (x - 1) / y + 1; }

#pragma endregion header

// MOD = 1e9 + 7;
vvi grid_bfs(vs &s, char start, int k) {
  const int vx[] = {0, 1, 0, -1}, vy[] = {1, 0, -1, 0};
  vvi min_cost(s.size(), vi(s[0].size(), -1));
  queue<pii> que;
  for (int i = 0; i < s.size(); i++) {
    for (int j = 0; j < s[i].size(); j++) {
      if (s[i][j] == start) {
        que.emplace(i, j);
        min_cost[i][j] = 0;
      }
    }
  }
  while (!que.empty()) {
    auto p = que.front();
    que.pop();
    for (int i = 0; i < 4; i++) {
      int ny = p.first, nx = p.second;
      rep(_, k) {
        ny += vy[i];
        nx += vx[i];
        if (nx < 0 || ny < 0 || nx >= s[0].size() || ny >= s.size())
          break;
        if (s[ny][nx] == '@')
          break;
        if (min_cost[ny][nx] != -1)
          continue;
        min_cost[ny][nx] = min_cost[p.first][p.second] + 1;
        que.emplace(ny, nx);
      }
    }
  }
  return min_cost;
}

void solve() {
  int h, w, k;
  int ans = 0;

  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  vector<string> s(h);
  rep(i, h) { cin >> s[i]; }
  s[x1][y1] = 'S';
  auto gb = grid_bfs(s, 'S', k);
  cout << gb[x2][y2] << endl;
}

// Failed to predict input format
#pragma region main
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << fixed << setprecision(15);

  solve();
}
#pragma endregion main


Fixed submission:
#pragma region header
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#define int long long
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define mp make_pair
#define mt make_tuple
#define rep1(i, n) for (decltype(+n) i = 0; i < (n); i++)
#define rrep1(i, n) for (auto i = n - 1; i > static_cast<decltype(i)>(-1); i--)
#define rep2(i, a, b) for (auto i = (a); i < (b); i++)
#define rrep2(i, a, b) for (auto i = b - 1; i >= a; i--)
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep(...) GET_MACRO(__VA_ARGS__, rrep2, rrep1)(__VA_ARGS__)
#define each(i, a) for (auto &&i : (a))
#define split_pair(f, s, p)                                                    \
  auto f = p.first;                                                            \
  auto s = p.second
using namespace std;

using ll = long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vd = vector<ld>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using pii = pair<int, int>;
using vp = vector<pii>;
using vvp = vector<vp>;
using vvvp = vector<vvp>;
using mii = map<int, int>;
using vm = vector<mii>;
using vvm = vector<vm>;
using vvvm = vector<vvm>;

const int INF = 1e18;
const int MOD = 1e9 + 7;
int mod(int a) { return (a % MOD + MOD) % MOD; }
int m_add(int a, int b) { return (a + b) % MOD; }
int m_add(int a, int b, int c) { return (a + b + c) % MOD; }
int m_sub(int a, int b) { return (a + MOD - b) % MOD; }
int m_mul(int a, int b) { return a * b % MOD; }
int m_mul(int a, int b, int c) { return a * b % MOD * c % MOD; }
int m_bipow(int x, int y) {
  if (y == 0)
    return 1;
  else if (y == 1)
    return x % MOD;
  else if (y % 2 == 0) {
    int z = m_bipow(x, (int)(y / 2));
    return m_mul(z, z);
  } else {
    int z = m_bipow(x, (int)(y / 2));
    return m_mul(z, z, x);
  }
}
int m_inv(int x) { return m_bipow(x, MOD - 2); }
int m_div(int a, int b) { return m_mul(a, m_inv(b)); }

template <class T> void SORT(T &a) { stable_sort(all(a)); }
template <class T> void RSORT(T &a) { stable_sort(rall(a)); }
template <class T> void rev(T &a) { reverse(rall(a)); }
template <class T> void uniq(T &a) { a.erase(unique(all(a)), end(a)); }
template <class T> auto min_of(T a) { return *min_element(all(a)); }
template <class T> auto max_of(T a) { return *max_element(all(a)); }
template <class T> int sum_of(T a) { return accumulate(all(a), 0ll); }
template <class T, class U> auto sum_of(T a, U init) {
  return accumulate(all(a), init);
}
template <class T, class U> int count_of(T a, U i) { return count(all(a), i); }
template <class T, class U> int lower_index(T a, U i) {
  return lower_bound(all(a), i) - begin(a);
} // use member func for set
template <class T, class U> int upper_index(T a, U i) {
  return upper_bound(all(a), i) - begin(a);
}
template <class T, class U> bool binary(T a, U i) {
  return binary_search(all(a), i);
}
template <class T, class U> bool exists(T a, U i) {
  return find(all(a), i) != end(a);
}
template <class T> int sz(T a) { return a.size(); };

template <class T> void COUT(T x) { cout << x << endl; }
template <class T, class U> void COUT(T x, U y) {
  cout << x << ' ' << y << endl;
}
template <class T, class U, class V> void COUT(T x, U y, V z) {
  cout << x << ' ' << y << ' ' << z << endl;
}
template <class T> void CSP(T x) { cout << x << ' '; }
template <class T> void CVEC(T v) {
  int c = v.size() - 1;
  for (size_t i = 0; i < c; i++)
    cout << v[i] << ' ';
  if (c > -1)
    cout << v[c];
  cout << endl;
}

template <class T> bool amin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool amax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <class T> vector<pair<T, int>> indexed_vector(vector<T> v) {
  int n = sz(v);
  vector<pair<T, int>> w(n);
  for (int i = 0; i < n; i++)
    w[i] = make_pair(v[i], i);
  return w;
}
template <class T, class S> vector<pair<T, S>> zip(vector<T> v, vector<S> w) {
  int n = min(sz(v), sz(w));
  vector<pair<T, S>> x(n);
  for (int i = 0; i < n; i++)
    x[i] = make_pair(v[i], w[i]);
  return x;
}
template <class T, class S>
pair<vector<T>, vector<S>> unzip(vector<pair<T, S>> v) {
  int n = sz(v);
  auto w = make_pair(vector<T>(n), vector<S>(n));
  for (int i = 0; i < n; i++) {
    w.first[i] = v[i].first;
    w.second[i] = v[i].second;
  }
  return w;
}

vs split(const string &s, string d) {
  vs elms;
  size_t offset = 0, d_size = d.size();
  while (true) {
    size_t next = s.find_first_of(d, offset);
    if (next == string::npos) {
      elms.push_back(s.substr(offset));
      return elms;
    }
    elms.push_back(s.substr(offset, next - offset));
    offset = next + d_size;
  }
}
vs split(const string &s, char d) { return split(s, string(1, d)); }
string join(const vs &v, const string d = "") {
  string s;
  if (!v.empty()) {
    s += v[0];
    for (size_t i = 1, c = v.size(); i < c; ++i) {
      if (!d.empty())
        s += d;
      s += v[i];
    }
  }
  return s;
}
string join(const vs &v, const char d) { return join(v, string(1, d)); }
string pad_left(string s, int width, char filler = '0') {
  int n = sz(s);
  if (n > width)
    return s.substr(n - width);
  return string(width - n, filler) + s;
}

int ceil_div(int x, int y) { return (x - 1) / y + 1; }

#pragma endregion header

// MOD = 1e9 + 7;
vvi grid_bfs(vs &s, char start, int k) {
  const int vx[] = {0, 1, 0, -1}, vy[] = {1, 0, -1, 0};
  vvi min_cost(s.size(), vi(s[0].size(), -1));
  queue<pii> que;
  for (int i = 0; i < s.size(); i++) {
    for (int j = 0; j < s[i].size(); j++) {
      if (s[i][j] == start) {
        que.emplace(i, j);
        min_cost[i][j] = 0;
      }
    }
  }
  while (!que.empty()) {
    auto p = que.front();
    que.pop();
    for (int i = 0; i < 4; i++) {
      int ny = p.first, nx = p.second;
      rep(_, k) {
        ny += vy[i];
        nx += vx[i];
        if (nx < 0 || ny < 0 || nx >= s[0].size() || ny >= s.size())
          break;
        if (s[ny][nx] == '@')
          break;
        int n_min = min_cost[ny][nx];
        if (n_min != -1) {
          if (min_cost[p.first][p.second] < n_min)
            continue;
          else
            break;
        }
        if (min_cost[ny][nx] != -1)
          continue;
        min_cost[ny][nx] = min_cost[p.first][p.second] + 1;
        que.emplace(ny, nx);
      }
    }
  }
  return min_cost;
}

void solve() {
  int h, w, k;
  int ans = 0;

  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  vector<string> s(h);
  rep(i, h) { cin >> s[i]; }
  s[x1][y1] = 'S';
  auto gb = grid_bfs(s, 'S', k);
  cout << gb[x2][y2] << endl;
}

// Failed to predict input format
#pragma region main
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << fixed << setprecision(15);

  solve();
}
#pragma endregion main