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

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

/* template start */

#define rep(i, a, b) for (long long i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...)                                                             \\
  std::cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << std::endl; }

template <typename Head, typename... Tail> void debug_out(Head h, Tail... t) {
  std::cerr << " " << h;
  if (sizeof...(t) > 0)
    std::cout << " :";
  debug_out(t...);
}

template <typename T1, typename T2>
std::ostream &operator<<(std::ostream &os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream &operator<<(std::ostream &os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return a > b && (a = b, true);
}

template <typename Num> constexpr Num mypow(Num a, unsigned long long b) {
  if (b == 0)
    return 1;
  if (a == 0)
    return 0;
  Num x = 1;
  while (b > 0) {
    if (b & 1)
      x *= a;
    a *= a;
    b >>= 1;
  }
  return x;
}

/* template end */

using ll = long long;

ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  ll h, w, k;
  std::cin >> h >> w >> k;

  ll sx, sy, gx, gy;
  std::cin >> sx >> sy >> gx >> gy;
  sx--;
  sy--;
  gx--;
  gy--;

  std::vector<std::string> grid(h);
  rep(i, 0, h) std::cin >> grid[i];

  constexpr ll INF = 1e10;

  std::vector<std::vector<ll>> d(h, std::vector<ll>(w, INF));
  std::vector<std::vector<std::bitset<4>>> used(h,
                                                std::vector<std::bitset<4>>(w));

  using P = std::pair<ll, ll>;

  std::queue<P> que;

  d[sx][sy] = 0;
  que.emplace(sx, sy);

  while (!que.empty()) {
    auto [nx, ny] = que.front();
    que.pop();
    rep(i, 0, 4) {
      ll tx = nx, ty = ny;
      rep(j, 0, k) {
        tx += dx[i];
        ty += dy[i];
        if (tx < 0 || tx >= h || ty < 0 || ty >= w)
          break;
        if (grid[tx][ty] == '@')
          break;
        if (d[tx][ty] < d[nx][ny] + 1)
          break;
        if (used[tx][ty][i])
          break;
        used[tx][ty][i] = true;
        d[tx][ty] = d[nx][ny] + 1;
        que.emplace(tx, ty);
      }
    }
  }

  if (d[gx][gy] == INF)
    std::cout << -1 << "\\n";
  else
    std::cout << d[gx][gy] << "\\n";

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

/* template start */

#define rep(i, a, b) for (long long i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...)                                                             \\
  std::cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << std::endl; }

template <typename Head, typename... Tail> void debug_out(Head h, Tail... t) {
  std::cerr << " " << h;
  if (sizeof...(t) > 0)
    std::cout << " :";
  debug_out(t...);
}

template <typename T1, typename T2>
std::ostream &operator<<(std::ostream &os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream &operator<<(std::ostream &os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return a > b && (a = b, true);
}

template <typename Num> constexpr Num mypow(Num a, unsigned long long b) {
  if (b == 0)
    return 1;
  if (a == 0)
    return 0;
  Num x = 1;
  while (b > 0) {
    if (b & 1)
      x *= a;
    a *= a;
    b >>= 1;
  }
  return x;
}

/* template end */

using ll = long long;

ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  ll h, w, k;
  std::cin >> h >> w >> k;

  ll sx, sy, gx, gy;
  std::cin >> sx >> sy >> gx >> gy;
  sx--;
  sy--;
  gx--;
  gy--;

  std::vector<std::string> grid(h);
  rep(i, 0, h) std::cin >> grid[i];

  constexpr ll INF = 1e10;

  std::vector<std::vector<ll>> d(h, std::vector<ll>(w, INF));

  using P = std::pair<ll, ll>;

  std::queue<P> que;

  d[sx][sy] = 0;
  que.emplace(sx, sy);

  while (!que.empty()) {
    auto [nx, ny] = que.front();
    que.pop();
    rep(i, 0, 4) {
      ll tx = nx, ty = ny;
      rep(j, 0, k) {
        tx += dx[i];
        ty += dy[i];
        if (tx < 0 || tx >= h || ty < 0 || ty >= w)
          break;
        if (grid[tx][ty] == '@')
          break;
        if (d[tx][ty] < d[nx][ny] + 1)
          break;
        d[tx][ty] = d[nx][ny] + 1;
        que.emplace(tx, ty);
      }
    }
  }

  if (d[gx][gy] == INF)
    std::cout << -1 << "\\n";
  else
    std::cout << d[gx][gy] << "\\n";

  return 0;
}