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

#include <bits/stdc++.h>
#define rep(i, a, b) for (i = a; i < b; i++)
#define rep2(i, a, b) for (i = a; i >= b; i--)
#define mod 1000000007
#define mod2 998244353
#define FIO                                                                    \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);                                                                  \\
  cout.tie(0)
#define INF 1e9 + 5
#define f first
#define s second
#define endl '\\n'
#define ll long long
#define ii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define vvi vector<vi>
#define vii vector<ii>
#define vpl vector<pll>
#define vvii vector<vii>
#define vll vector<ll>
#define vb vector<bool>
#define pb push_back
#define mk make_pair
#define eb emplace_back
#define pg priority_queue<ll, vector<ll>, greater<ll>>
#define pq priority_queue<ll>
#define sz(a) a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define cset(a) __builtin_popcountll(a)
#define FILL(a, b, T) fill_n((T *)a, sizeof(a) / sizeof(T), b)
// #define debug(x) cerr << #x << " is " << x << endl;
using namespace std;
#define error(args...)                                                         \\
  {                                                                            \\
    string _s = #args;                                                         \\
    replace(_s.begin(), _s.end(), ',', ' ');                                   \\
    stringstream _ss(_s);                                                      \\
    istream_iterator<string> _it(_ss);                                         \\
    err(_it, args);                                                            \\
  }
#define pis pair<ll, pll>
void err(istream_iterator<string> it) {}
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  err(++it, args...);
}
template <typename A, typename B> string to_string(pair<A, B> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
// unordered_map<long long, int, custom_hash> safe_map;
// FOR VIEWERS, CODE STARTS HERE
ll r[4] = {-1, 1, 0, 0};
ll c[4] = {0, 0, 1, -1};
int main() {
  FIO;
  ll t, n, m, q, maxx, i, j, k1, k2, k3, k, x, y, flag, sum, cnt, ans, minn,
      cur;
  cin >> n >> m >> k1;
  ll x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  vector<string> a(n);
  vector<vector<ll>> dist(n + 1, vector<ll>(m + 1, INF));
  rep(i, 0, n) cin >> a[i];
  queue<pll> qw;
  qw.push({x1, y1});
  dist[x1][y1] = 0;
  while (!qw.empty()) {
    x1 = qw.front().f;
    y1 = qw.front().s;
    qw.pop();
    if (x1 == x2 and y1 == y2) {
      cout << dist[x2][y2] << endl;
      return 0;
    }
    rep(i, 0, 4) {
      rep(k, 1, k1 + 1) {
        x = x1 + r[i] * k;
        y = y1 + c[i] * k;
        if (x < 0 or x >= n or y < 0 or y >= m)
          break;
        if (a[x][y] == '@' or dist[x1][y1] >= dist[x][y])
          break;
        if (dist[x1][y1] + 1 < dist[x][y]) {
          qw.push({x, y});
          dist[x][y] = dist[x1][y1] + 1;
        }
      }
    }
  }
  cout << "-1\\n";
  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, a, b) for (i = a; i < b; i++)
#define rep2(i, a, b) for (i = a; i >= b; i--)
#define mod 1000000007
#define mod2 998244353
#define FIO                                                                    \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);                                                                  \\
  cout.tie(0)
#define INF 1e9 + 5
#define f first
#define s second
#define endl '\\n'
#define ll int
#define ii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define vvi vector<vi>
#define vii vector<ii>
#define vpl vector<pll>
#define vvii vector<vii>
#define vll vector<ll>
#define vb vector<bool>
#define pb push_back
#define mk make_pair
#define eb emplace_back
#define pg priority_queue<ll, vector<ll>, greater<ll>>
#define pq priority_queue<ll>
#define sz(a) a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define cset(a) __builtin_popcountll(a)
#define FILL(a, b, T) fill_n((T *)a, sizeof(a) / sizeof(T), b)
// #define debug(x) cerr << #x << " is " << x << endl;
using namespace std;
#define error(args...)                                                         \\
  {                                                                            \\
    string _s = #args;                                                         \\
    replace(_s.begin(), _s.end(), ',', ' ');                                   \\
    stringstream _ss(_s);                                                      \\
    istream_iterator<string> _it(_ss);                                         \\
    err(_it, args);                                                            \\
  }
#define pis pair<ll, pll>
void err(istream_iterator<string> it) {}
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  err(++it, args...);
}
template <typename A, typename B> string to_string(pair<A, B> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
// unordered_map<long long, int, custom_hash> safe_map;
// FOR VIEWERS, CODE STARTS HERE
ll r[4] = {-1, 1, 0, 0};
ll c[4] = {0, 0, 1, -1};
int main() {
  FIO;
  ll t, n, m, q, maxx, i, j, k1, k2, k3, k, x, y, flag, sum, cnt, ans, minn,
      cur;
  cin >> n >> m >> k1;
  ll x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  x1--;
  y1--;
  x2--;
  y2--;
  vector<string> a(n);
  vector<vector<ll>> dist(n + 1, vector<ll>(m + 1, INF));
  rep(i, 0, n) cin >> a[i];
  queue<pll> qw;
  qw.push({x1, y1});
  dist[x1][y1] = 0;
  while (!qw.empty()) {
    x1 = qw.front().f;
    y1 = qw.front().s;
    qw.pop();
    if (x1 == x2 and y1 == y2) {
      cout << dist[x2][y2] << endl;
      return 0;
    }
    rep(i, 0, 4) {
      rep(k, 1, k1 + 1) {
        x = x1 + r[i] * k;
        y = y1 + c[i] * k;
        if (x < 0 or x >= n or y < 0 or y >= m)
          break;
        if (a[x][y] == '@')
          break;
        if (dist[x1][y1] + 1 < dist[x][y]) {
          qw.push({x, y});
          dist[x][y] = dist[x1][y1] + 1;
        }
      }
    }
  }
  cout << "-1\\n";
  return 0;
}