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

#include <bits/stdc++.h>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

ll gcd(ll n, ll m) {
  ll tmp;
  while (m != 0) {
    tmp = n % m;
    n = m;
    m = tmp;
  }
  return n;
}

ll lcm(ll n, ll m) {
  return abs(n) / gcd(n, m) * abs(m); // gl=xy
}

using namespace std;

int k;
int cnt;

vector<vector<int>> grid_bfs(int h, int w, int x, int y, vector<string> &maze,
                             char obstacle = '#') {
  const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}; // 4方向移動
  const int init = 1e7;
  vector<vector<int>> d(h, vector<int>(w, init));
  d[x][y] = 0;
  queue<pair<int, int>> q;
  pair<int, int> p;
  q.emplace(x, y);
  while (!q.empty()) {
    p = q.front();
    q.pop();
    for (int i = 0; i < 4; ++i) {
      REP(j, 1, k + 1) {
        int nx = p.first + dx[i] * j;
        int ny = p.second + dy[i] * j;
        if (!(0 <= nx && nx < h && 0 <= ny && ny < w))
          break;
        if (maze[nx][ny] == obstacle)
          break;
        if (d[nx][ny] == init) {
          cnt = 0;
          q.emplace(make_pair(nx, ny));
          d[nx][ny] = d[p.first][p.second] + 1;
        } else
          ++cnt;
        if (cnt >= 1000)
          break;
      }
    }
  }
  return d; // initを含むことに注意
}

void solve() {
  int h, w;
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  cnt = 0;
  vector<string> c(h);
  rep(i, h) cin >> c[i];
  auto d = grid_bfs(h, w, x1, y1, c, '@');
  ll ans = d[x2][y2];
  if (ans == 1e7)
    cout << -1;
  else
    cout << ans;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

ll gcd(ll n, ll m) {
  ll tmp;
  while (m != 0) {
    tmp = n % m;
    n = m;
    m = tmp;
  }
  return n;
}

ll lcm(ll n, ll m) {
  return abs(n) / gcd(n, m) * abs(m); // gl=xy
}

using namespace std;

int k;

vector<vector<int>> grid_bfs(int h, int w, int x, int y, vector<string> &maze,
                             char obstacle = '#') {
  const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}; // 4方向移動
  const int init = 1e7;
  vector<vector<int>> d(h, vector<int>(w, init));
  d[x][y] = 0;
  queue<pair<int, int>> q;
  pair<int, int> p;
  q.emplace(x, y);
  while (!q.empty()) {
    p = q.front();
    q.pop();
    for (int i = 0; i < 4; ++i) {
      REP(j, 1, k + 1) {
        int nx = p.first + dx[i] * j;
        int ny = p.second + dy[i] * j;
        if (!(0 <= nx && nx < h && 0 <= ny && ny < w))
          break;
        if (maze[nx][ny] == obstacle)
          break;
        if (d[nx][ny] == init) {
          q.emplace(make_pair(nx, ny));
          d[nx][ny] = d[p.first][p.second] + 1;
        }
      }
    }
  }
  return d; // initを含むことに注意
}

void solve() {
  int h, w;
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  vector<string> c(h);
  rep(i, h) cin >> c[i];
  auto d = grid_bfs(h, w, x1, y1, c, '@');
  ll ans = d[x2][y2];
  if (ans == 1e7)
    cout << -1;
  else
    cout << ans;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}