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

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = b - 1; i >= a; i--)
#define ALL(a) a.begin(), a.end()
using pii = pair<int, int>;
using piii = pair<pii, int>;
using pll = pair<long long, long long>;
using plll = pair<pll, long long>;
// #pragma GCC optimize("Ofast")
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define pb push_back
#define mp make_pair
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define isSquare(x) (sqrt(x) * sqrt(x) == x)
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
};
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
};
inline void in(void) { return; }
template <typename First, typename... Rest>
void in(First &first, Rest &...rest) {
  cin >> first;
  in(rest...);
  return;
}
inline void out(void) {
  cout << "\\n";
  return;
}
template <typename First, typename... Rest>
void out(First first, Rest... rest) {
  cout << first << " ";
  out(rest...);
  return;
}
const double EPS = 1e-9;
const int mod = 1e9 + 7;
// const int mod = 998244353;
const int INF = 1e9;
const long long INFLL = 1e18;
void iosetup() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}
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 <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T>
pair<S, T> operator*(const pair<S, T> &s, const S &t) {
  return pair<S, T>(s.first * t, s.second * t);
}
template <typename T> void Exit(T first) {
  cout << first << endl;
  exit(0);
};
template <int mod> struct ModInt {
  unsigned x;
  ModInt() : x(0) {}
  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }
  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  static int get_mod() { return mod; }
};
using modint = ModInt<mod>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const pii dxy[4] = {pii(1, 0), pii(0, 1), pii(-1, 0), pii(0, -1)};
bool range(int a, int b, int x) {
  if (a <= x and x < b)
    return true;
  else
    return false;
}
bool range(int a, int b, int c, int d, pii p) {
  if (a <= p.first and p.first < b and c <= p.second and p.second < d)
    return true;
  else
    return false;
}

using P = tuple<int, int, int>;
int main() {
  iosetup();
  int h, w, k;
  cin >> h >> w >> k;
  int sx, sy, tx, ty;
  cin >> sx >> sy >> tx >> ty;
  sx--, sy--, tx--, ty--;
  vector<string> C(h);
  cin >> C;
  auto dist = make_vec<int>(h, w);
  rep(i, 0, h) rep(j, 0, w) dist[i][j] = INF;
  dist[sx][sy] = 0;
  queue<pii> que;
  que.emplace(sx, sy);
  while (!que.empty()) {
    auto [x, y] = que.front();
    que.pop();
    rep(v, 0, 4) {
      int nx = x;
      int ny = y;
      rep(i, 1, k + 1) {
        nx += dx[v];
        ny += dy[v];
        if (nx < 0 or nx >= h)
          break;
        if (ny < 0 or ny >= w)
          break;
        if (C[nx][ny] == '@')
          break;
        if (dist[nx][ny] <= dist[x][y])
          break;
        if (dist[nx][ny] == INF) {
          dist[nx][ny] = dist[x][y] + 1;
          que.emplace(nx, ny);
        }
      }
    }
  }
  if (dist[tx][ty] == INF)
    cout << -1 << endl;
  else
    cout << dist[tx][ty] << endl;

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = b - 1; i >= a; i--)
#define ALL(a) a.begin(), a.end()
using pii = pair<int, int>;
using piii = pair<pii, int>;
using pll = pair<long long, long long>;
using plll = pair<pll, long long>;
// #pragma GCC optimize("Ofast")
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define pb push_back
#define mp make_pair
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define isSquare(x) (sqrt(x) * sqrt(x) == x)
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
};
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
};
inline void in(void) { return; }
template <typename First, typename... Rest>
void in(First &first, Rest &...rest) {
  cin >> first;
  in(rest...);
  return;
}
inline void out(void) {
  cout << "\\n";
  return;
}
template <typename First, typename... Rest>
void out(First first, Rest... rest) {
  cout << first << " ";
  out(rest...);
  return;
}
const double EPS = 1e-9;
const int mod = 1e9 + 7;
// const int mod = 998244353;
const int INF = 1e9;
const long long INFLL = 1e18;
void iosetup() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}
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 <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T>
pair<S, T> operator*(const pair<S, T> &s, const S &t) {
  return pair<S, T>(s.first * t, s.second * t);
}
template <typename T> void Exit(T first) {
  cout << first << endl;
  exit(0);
};
template <int mod> struct ModInt {
  unsigned x;
  ModInt() : x(0) {}
  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }
  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  static int get_mod() { return mod; }
};
using modint = ModInt<mod>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const pii dxy[4] = {pii(1, 0), pii(0, 1), pii(-1, 0), pii(0, -1)};
bool range(int a, int b, int x) {
  if (a <= x and x < b)
    return true;
  else
    return false;
}
bool range(int a, int b, int c, int d, pii p) {
  if (a <= p.first and p.first < b and c <= p.second and p.second < d)
    return true;
  else
    return false;
}

using P = tuple<int, int, int, int, int>;
int main() {
  iosetup();
  int h, w, k;
  cin >> h >> w >> k;
  int sx, sy, tx, ty;
  cin >> sx >> sy >> tx >> ty;
  sx--, sy--, tx--, ty--;
  vector<vector<char>> C(h, vector<char>(w));
  rep(i, 0, h) cin >> C[i];
  auto compare = [](P a, P b) { return get<2>(a) > get<2>(b); };
  priority_queue<P, vector<P>, decltype(compare)> q{compare};
  q.emplace(sx, sy, 0, -1, 1);
  vector<vector<vector<int>>> dp(h,
                                 vector<vector<int>>(w, vector<int>(4, INF)));
  dp[sx][sy][0] = 0;
  dp[sx][sy][1] = 0;
  dp[sx][sy][2] = 0;
  dp[sx][sy][3] = 0;
  while (!q.empty()) {
    auto now = q.top();
    q.pop();
    int x = get<0>(now);
    int y = get<1>(now);
    int cos = get<2>(now);
    int dir = get<3>(now);
    int num = get<4>(now);

    // cerr << x << " " <<  y << " " << cos << " " << dir << " " << num << endl;
    if (dp[x][y][dir] < cos)
      continue;
    // dp[x][y][dir] = cos;
    rep(i, 0, 4) {
      int nx = x + dx[i], ny = y + dy[i];
      if (nx < 0 or nx >= h)
        continue;
      if (ny < 0 or ny >= w)
        continue;
      if (C[nx][ny] == '@')
        continue;
      int nn = 0, nc = cos;
      if (i != dir) {
        nn = 1;
        nc++;
      } else {
        if (num == k) {
          nn = 1;
          nc++;
        } else {
          nn = num + 1;
        }
      }
      chmin(dp[nx][ny][i], nc);
      if (nc == cos)
        q.emplace(nx, ny, nc, i, nn);
      else
        q.emplace(nx, ny, nc, i, nn);
    }
  }
  int ans = INF;
  // rep(i, 0, h){
  //     rep(j, 0, w){
  //         int t = INF;
  //         rep(k, 0, 4){
  //             if(dp[i][j][k]!=-1)chmin(t, dp[i][j][k]);
  //         }
  //         if(t == INF) cerr << -1 << " ";
  //         else cerr << t << " ";
  //     }
  //     cerr << endl;
  // }
  rep(i, 0, 4) {
    if (dp[tx][ty][i] != -1)
      chmin(ans, dp[tx][ty][i]);
  }
  if (ans == INF)
    Exit(-1);
  // ans--;
  cout << ans << endl;

  return 0;
}