Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <chrono>
#include <climits>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

template <class T1, class T2>
ostream &operator<<(ostream &out, const pair<T1, T2> p) {
  out << '(' << p.first << ',' << p.second << ')';
  return out;
}

template <class T1, class T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
  in >> p.first >> p.second;
  return in;
}

template <class T> istream &operator>>(istream &in, vector<T> &v) {
  for (T &x : v)
    in >> x;
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &v) {
  for (const vector<T> &x : v)
    out << x << '\n';
  return out;
}

template <class T> ostream &operator<<(ostream &out, const vector<T> &v) {
  for (const T &x : v)
    out << x << ' ';
  return out;
}

long long gcd(long long a, long long b) {
  if (b > a)
    swap(a, b);
  return (b ? gcd(b, a % b) : a);
}

using ll = long long;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
using tiii = pair<pair<int, int>, int>;
using vi = vector<int>;
using vl = vector<long long>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<long long>>;

#define F first
#define S second
#define First first.first
#define Second first.second
#define Third second
#define mp make_pair
#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define per(i, b, a) for (int i = (b); i > (a); i--)
#define all(x) x.begin(), x.end()
#define ret(x) return cout << x, 0;
#define throwex throw runtime_error("Found the error.");

const int h = 1000000007;

signed main() {
  ios::sync_with_stdio(false);
#ifdef ONLINE_JUDGE
  cin.tie(nullptr);
  cout.tie(nullptr);
  cerr.setstate(ios::failbit);
#endif

  int h, w, k;
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--, y1--, x2--, y2--;
  vector<string> grid(h);
  cin >> grid;
  vector<vvi> vis(4, vvi(h, vi(w)));
  queue<pii> q;
  q.push({x1, y1});
  vvi vis_time(h, vi(w, INT_MAX));
  vis_time[x1][y1] = 0;
  vector<pii> dir{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
  while (!q.empty()) {
    pii cur = q.front();
    q.pop();
    rep(i, 0, 4) vis[i][cur.F][cur.S] = true;
    rep(i, 0, 4) {
      pii nex = cur;
      rep(_, 0, k) {
        nex = {nex.F + dir[i].F, nex.S + dir[i].S};
        if (nex.F < 0 or nex.F == h or nex.S < 0 or nex.S == w)
          break;
        if (grid[nex.F][nex.S] == '@' or
            vis_time[nex.F][nex.S] <= vis_time[cur.F][cur.S])
          break;
        vis[i][nex.F][nex.S] = true;
        if (vis_time[nex.F][nex.S] == INT_MAX)
          vis_time[nex.F][nex.S] = vis_time[cur.F][cur.S] + 1;
        q.push(nex);
      }
    }
  }
  cout << (vis_time[x2][y2] == INT_MAX ? -1 : vis_time[x2][y2]);
}


Fixed submission:
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <chrono>
#include <climits>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

template <class T1, class T2>
ostream &operator<<(ostream &out, const pair<T1, T2> p) {
  out << '(' << p.first << ',' << p.second << ')';
  return out;
}

template <class T1, class T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
  in >> p.first >> p.second;
  return in;
}

template <class T> istream &operator>>(istream &in, vector<T> &v) {
  for (T &x : v)
    in >> x;
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &v) {
  for (const vector<T> &x : v)
    out << x << '\n';
  return out;
}

template <class T> ostream &operator<<(ostream &out, const vector<T> &v) {
  for (const T &x : v)
    out << x << ' ';
  return out;
}

long long gcd(long long a, long long b) {
  if (b > a)
    swap(a, b);
  return (b ? gcd(b, a % b) : a);
}

using ll = long long;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
using tiii = pair<pair<int, int>, int>;
using vi = vector<int>;
using vl = vector<long long>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<long long>>;

#define F first
#define S second
#define First first.first
#define Second first.second
#define Third second
#define mp make_pair
#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define per(i, b, a) for (int i = (b); i > (a); i--)
#define all(x) x.begin(), x.end()
#define ret(x) return cout << x, 0;
#define throwex throw runtime_error("Found the error.");

const int h = 1000000007;

signed main() {
  ios::sync_with_stdio(false);
#ifdef ONLINE_JUDGE
  cin.tie(nullptr);
  cout.tie(nullptr);
  cerr.setstate(ios::failbit);
#endif

  int h, w, k;
  cin >> h >> w >> k;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--, y1--, x2--, y2--;
  vector<string> grid(h);
  cin >> grid;
  vector<vvi> vis(4, vvi(h, vi(w)));
  queue<pii> q;
  q.push({x1, y1});
  vvi vis_time(h, vi(w, INT_MAX));
  vis_time[x1][y1] = 0;
  vector<pii> dir{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
  while (!q.empty()) {
    pii cur = q.front();
    q.pop();
    rep(i, 0, 4) vis[i][cur.F][cur.S] = true;
    rep(i, 0, 4) {
      pii nex = cur;
      rep(_, 0, k) {
        nex = {nex.F + dir[i].F, nex.S + dir[i].S};
        if (nex.F < 0 or nex.F == h or nex.S < 0 or nex.S == w)
          break;
        if (grid[nex.F][nex.S] == '@' or
            vis_time[nex.F][nex.S] <= vis_time[cur.F][cur.S] or
            vis[i][nex.F][nex.S])
          break;
        vis[i][nex.F][nex.S] = true;
        if (vis_time[nex.F][nex.S] == INT_MAX)
          vis_time[nex.F][nex.S] = vis_time[cur.F][cur.S] + 1;
        q.push(nex);
      }
    }
  }
  cout << (vis_time[x2][y2] == INT_MAX ? -1 : vis_time[x2][y2]);
}