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

// #pragma GCC optimize ("O3","unroll-loops")
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <iomanip>
#include <iostream>

#include <algorithm>
#include <cmath>
#include <functional>
#include <numeric>

#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>

#define TEST                                                                   \\
  { IS_TEST = true; }
#define fi first
#define se second
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)
#define uppb upper_bound
#define lowb lower_bound

using namespace std;
using ll = int_fast64_t;
using v_b = vector<bool>;
using v_ll = vector<ll>;
using str = string;
using v_str = vector<string>;
using p_ll = pair<ll, ll>;
using vv_b = vector<v_b>;
using vv_ll = vector<v_ll>;
using vp_ll = vector<p_ll>;
using vvv_ll = vector<vv_ll>;
using vvp_ll = vector<vp_ll>;
using ld = long double;
using v_ld = vector<ld>;
using vv_ld = vector<v_ld>;

bool IS_TEST = false;
ll ll_min64 = 1LL << 63;
ll ll_max64 = ~ll_min64;
ll ll_min32 = 1LL << 31;
ll ll_max32 = ~ll_min32;

ll MOD = 1000000007;

/*displaying functions for debug*/
template <class T> void show2(const T &x) { cerr << x; }
template <class T1, class T2> void show2(const pair<T1, T2> &x) {
  cerr << "{" << show2(x.first) << "," << show2(x.second) << "}";
}
template <class T> void show(const T &x) {
  if (!IS_TEST)
    return;
  show2(x);
  cerr << "\\n";
}
template <class T> void v_show(const T &v, ll n = -1) {
  if (!IS_TEST)
    return;
  auto itr = v.begin();
  ll m = n;
  while (itr != v.end() && m != 0) {
    show2(*itr);
    cerr << " ";
    itr++;
    m--;
  }
  cerr << "\\n";
}
template <class T> void vv_show(const T &v, ll n = -1) {
  if (!IS_TEST)
    return;
  cerr << "--------------------------------\\n";
  auto itr = v.begin();
  ll m = n;
  while (itr != v.end() && m != 0) {
    v_show(*itr, n);
    itr++;
    m--;
  }
  cerr << "--------------------------------\\n";
}
/*--------------------------------*/

/*loading integers*/
void load(ll &x1) { cin >> x1; }
void load(ll &x1, ll &x2) { cin >> x1 >> x2; }
void load(ll &x1, ll &x2, ll &x3) { cin >> x1 >> x2 >> x3; }
void load(ll &x1, ll &x2, ll &x3, ll &x4) { cin >> x1 >> x2 >> x3 >> x4; }
void v_load(ll n, v_ll &v1, ll head = 0, ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld", &v1[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, ll head = 0, ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld", &v1[i + head], &v2[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, v_ll &v3, ll head = 0, ll tail = 0,
            ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  v3.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld%lld", &v1[i + head], &v2[i + head], &v3[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, v_ll &v3, v_ll &v4, ll head = 0,
            ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  v3.assign(m, init);
  v4.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld%lld%lld", &v1[i + head], &v2[i + head], &v3[i + head],
          &v4[i + head]);
  }
}
/*--------------------------------*/

/*output*/
template <class T> void put(T x) { cout << x << "\\n"; }
template <class T1, class T2> void put(T1 x, T2 y) {
  cout << x << " " << y << "\\n";
}
/*---*/

v_ll local_sort(ll x1 = ll_max64, ll x2 = ll_max64, ll x3 = ll_max64,
                ll x4 = ll_max64) {
  v_ll x{x1, x2, x3, x4};
  sort(x.begin(), x.end());
  return x;
}

ll max(ll x, ll y) { return x > y ? x : y; }
ll min(ll x, ll y) { return x < y ? x : y; }

ll max(v_ll::iterator b, v_ll::iterator e) {
  ll ans = *b;
  while (b < e) {
    ans = max(ans, *b);
    b++;
  }
  return ans;
}
ll argmax(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0, cnt = 0, val = *b;
  while (b < e) {
    if (val < *b) {
      ans = cnt;
      val = *b;
    }
    cnt++;
    b++;
  }
  return ans;
}
ll min(v_ll::iterator b, v_ll::iterator e) {
  ll ans = *b;
  while (b < e) {
    ans = min(ans, *b);
    b++;
  }
  return ans;
}
ll argmin(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0, cnt = 0, val = *b;
  while (b < e) {
    if (val > *b) {
      ans = cnt;
      val = *b;
    }
    cnt++;
    b++;
  }
  return ans;
}
ll sum(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0;
  while (b < e) {
    ans += *b;
    b++;
  }
  return ans;
}

template <class T> bool chmax(T &x, const T &y) {
  if (x >= y)
    return false;
  x = y;
  return true;
}
template <class T> bool chmin(T &x, const T &y) {
  if (x <= y)
    return false;
  x = y;
  return true;
}

template <class T> void quit(T x) {
  cout << x << endl;
  exit(0);
}
void yesno(bool x) { cout << (x ? "Yes" : "No") << endl; }

ll roundup(ll x, ll y) { return (x - 1) / y + 1; }
ll rem(ll x, ll y) {
  ll z = x % y;
  return z >= 0 ? z : z + y;
}

template <typename T> v_ll index_sort(const vector<T> &ref) {
  v_ll idx(ref.size());
  iota(idx.begin(), idx.end(), 0);
  sort(idx.begin(), idx.end(), [&](auto &x, auto &y) {
    if (ref[x] < ref[y])
      return true;
  });
}

// setprecision(digit)
// sort(##.begin(),##.end(),[&](auto &x, auto &y){if (x<y) return true;});

struct dat {
  ll x, y, d;
  dat(ll x, ll y, ll d) : x(x), y(y), d(d) {}
};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll ans = -1;
  ll H, W, K;
  ll x1, y1, x2, y2;
  cin >> H >> W >> K;
  cin >> x1 >> y1 >> x2 >> y2;

  v_str C(H, "");
  x1--;
  y1--;
  x2--;
  y2--;
  for (ll i = 0; i < H; i++) {
    cin >> C[i];
  }
  queue<dat> Q;
  Q.push(dat(x1, y1, 0));
  vv_b arv(H, v_b(W, false));
  vv_b chk(H, v_b(W, false));
  while (!Q.empty()) {
    auto f = Q.front();
    Q.pop();
    if (arv[f.x][f.y])
      continue;
    arv[f.x][f.y] = true;
    chk[f.x][f.y] = true;
    // cout << f.x << " " << f.y <<" "<<f.d<< endl;
    if (f.x == x2 && f.y == y2) {
      ans = f.d;
      break;
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x - i;
      ny = f.y;
      if (nx >= 0 && C[nx][ny] == '.' && !chk[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
        chk[nx][ny] = true;
      } else if (nx >= 0 && C[nx][ny] == '.' && !arv[nx][ny]) {
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x + i;
      ny = f.y;
      if (nx < H && C[nx][ny] == '.' && !chk[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
        chk[nx][ny] = true;
      } else if (nx < H && C[nx][ny] == '.' && !arv[nx][ny]) {
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x;
      ny = f.y - i;
      if (ny >= 0 && C[nx][ny] == '.' && !chk[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
        chk[nx][ny] = true;
      } else if (ny >= 0 && C[nx][ny] == '.' && !arv[nx][ny]) {
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x;
      ny = f.y + i;
      if (ny < W && C[nx][ny] == '.' && !chk[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
        chk[nx][ny] = true;
      } else if (ny < W && C[nx][ny] == '.' && !arv[nx][ny]) {
      } else {
        break;
      }
    }
  }
  cout << ans << "\\n";
}


Error: TLE

Fixed submission:

// #pragma GCC optimize ("O3","unroll-loops")
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <iomanip>
#include <iostream>

#include <algorithm>
#include <cmath>
#include <functional>
#include <numeric>

#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>

#define TEST                                                                   \\
  { IS_TEST = true; }
#define fi first
#define se second
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)
#define uppb upper_bound
#define lowb lower_bound

using namespace std;
using ll = int_fast64_t;
using v_b = vector<bool>;
using v_ll = vector<ll>;
using str = string;
using v_str = vector<string>;
using p_ll = pair<ll, ll>;
using vv_b = vector<v_b>;
using vv_ll = vector<v_ll>;
using vp_ll = vector<p_ll>;
using vvv_ll = vector<vv_ll>;
using vvp_ll = vector<vp_ll>;
using ld = long double;
using v_ld = vector<ld>;
using vv_ld = vector<v_ld>;

bool IS_TEST = false;
ll ll_min64 = 1LL << 63;
ll ll_max64 = ~ll_min64;
ll ll_min32 = 1LL << 31;
ll ll_max32 = ~ll_min32;

ll MOD = 1000000007;

/*displaying functions for debug*/
template <class T> void show2(const T &x) { cerr << x; }
template <class T1, class T2> void show2(const pair<T1, T2> &x) {
  cerr << "{" << show2(x.first) << "," << show2(x.second) << "}";
}
template <class T> void show(const T &x) {
  if (!IS_TEST)
    return;
  show2(x);
  cerr << "\\n";
}
template <class T> void v_show(const T &v, ll n = -1) {
  if (!IS_TEST)
    return;
  auto itr = v.begin();
  ll m = n;
  while (itr != v.end() && m != 0) {
    show2(*itr);
    cerr << " ";
    itr++;
    m--;
  }
  cerr << "\\n";
}
template <class T> void vv_show(const T &v, ll n = -1) {
  if (!IS_TEST)
    return;
  cerr << "--------------------------------\\n";
  auto itr = v.begin();
  ll m = n;
  while (itr != v.end() && m != 0) {
    v_show(*itr, n);
    itr++;
    m--;
  }
  cerr << "--------------------------------\\n";
}
/*--------------------------------*/

/*loading integers*/
void load(ll &x1) { cin >> x1; }
void load(ll &x1, ll &x2) { cin >> x1 >> x2; }
void load(ll &x1, ll &x2, ll &x3) { cin >> x1 >> x2 >> x3; }
void load(ll &x1, ll &x2, ll &x3, ll &x4) { cin >> x1 >> x2 >> x3 >> x4; }
void v_load(ll n, v_ll &v1, ll head = 0, ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld", &v1[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, ll head = 0, ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld", &v1[i + head], &v2[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, v_ll &v3, ll head = 0, ll tail = 0,
            ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  v3.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld%lld", &v1[i + head], &v2[i + head], &v3[i + head]);
  }
}
void v_load(ll n, v_ll &v1, v_ll &v2, v_ll &v3, v_ll &v4, ll head = 0,
            ll tail = 0, ll init = 0) {
  ll m = n + head + tail;
  v1.assign(m, init);
  v2.assign(m, init);
  v3.assign(m, init);
  v4.assign(m, init);
  for (ll i = 0; i < n; i++) {
    scanf("%lld%lld%lld%lld", &v1[i + head], &v2[i + head], &v3[i + head],
          &v4[i + head]);
  }
}
/*--------------------------------*/

/*output*/
template <class T> void put(T x) { cout << x << "\\n"; }
template <class T1, class T2> void put(T1 x, T2 y) {
  cout << x << " " << y << "\\n";
}
/*---*/

v_ll local_sort(ll x1 = ll_max64, ll x2 = ll_max64, ll x3 = ll_max64,
                ll x4 = ll_max64) {
  v_ll x{x1, x2, x3, x4};
  sort(x.begin(), x.end());
  return x;
}

ll max(ll x, ll y) { return x > y ? x : y; }
ll min(ll x, ll y) { return x < y ? x : y; }

ll max(v_ll::iterator b, v_ll::iterator e) {
  ll ans = *b;
  while (b < e) {
    ans = max(ans, *b);
    b++;
  }
  return ans;
}
ll argmax(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0, cnt = 0, val = *b;
  while (b < e) {
    if (val < *b) {
      ans = cnt;
      val = *b;
    }
    cnt++;
    b++;
  }
  return ans;
}
ll min(v_ll::iterator b, v_ll::iterator e) {
  ll ans = *b;
  while (b < e) {
    ans = min(ans, *b);
    b++;
  }
  return ans;
}
ll argmin(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0, cnt = 0, val = *b;
  while (b < e) {
    if (val > *b) {
      ans = cnt;
      val = *b;
    }
    cnt++;
    b++;
  }
  return ans;
}
ll sum(v_ll::iterator b, v_ll::iterator e) {
  ll ans = 0;
  while (b < e) {
    ans += *b;
    b++;
  }
  return ans;
}

template <class T> bool chmax(T &x, const T &y) {
  if (x >= y)
    return false;
  x = y;
  return true;
}
template <class T> bool chmin(T &x, const T &y) {
  if (x <= y)
    return false;
  x = y;
  return true;
}

template <class T> void quit(T x) {
  cout << x << endl;
  exit(0);
}
void yesno(bool x) { cout << (x ? "Yes" : "No") << endl; }

ll roundup(ll x, ll y) { return (x - 1) / y + 1; }
ll rem(ll x, ll y) {
  ll z = x % y;
  return z >= 0 ? z : z + y;
}

template <typename T> v_ll index_sort(const vector<T> &ref) {
  v_ll idx(ref.size());
  iota(idx.begin(), idx.end(), 0);
  sort(idx.begin(), idx.end(), [&](auto &x, auto &y) {
    if (ref[x] < ref[y])
      return true;
  });
}

// setprecision(digit)
// sort(##.begin(),##.end(),[&](auto &x, auto &y){if (x<y) return true;});

struct dat {
  ll x, y, d;
  dat(ll x, ll y, ll d) : x(x), y(y), d(d) {}
};

int main() {
  ll ans = -1;
  ll H, W, K;
  ll x1, y1, x2, y2;
  cin >> H >> W >> K;
  cin >> x1 >> y1 >> x2 >> y2;

  v_str C(H, "");
  x1--;
  y1--;
  x2--;
  y2--;
  for (ll i = 0; i < H; i++) {
    cin >> C[i];
  }
  queue<dat> Q;
  Q.push(dat(x1, y1, 0));
  vv_b arv(H, v_b(W, false));
  while (!Q.empty()) {
    auto f = Q.front();
    Q.pop();
    if (arv[f.x][f.y])
      continue;
    arv[f.x][f.y] = true;
    // cout << f.x << " " << f.y << endl;
    if (f.x == x2 && f.y == y2) {
      ans = f.d;
      break;
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x - i;
      ny = f.y;
      if (nx >= 0 && C[nx][ny] == '.' && !arv[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x + i;
      ny = f.y;
      if (nx < H && C[nx][ny] == '.' && !arv[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x;
      ny = f.y - i;
      if (ny >= 0 && C[nx][ny] == '.' && !arv[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
      } else {
        break;
      }
    }
    for (ll i = 1; i <= K; i++) {
      ll nx, ny;
      nx = f.x;
      ny = f.y + i;
      if (ny < W && C[nx][ny] == '.' && !arv[nx][ny]) {
        Q.push(dat(nx, ny, f.d + 1));
      } else {
        break;
      }
    }
  }
  cout << ans << "\\n";
}