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

#pragma GCC target("avx")
// #pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define DB double
#define LD long double
#define ST string
#define BS bitset
#define PA pair<LL, LL>
#define VE vector
#define VL vector<LL>
#define VP vector<pair<LL, LL>>
#define VVL vector<vector<LL>>
#define PQ priority_queue
#define PQS priority_queue<LL, vector<LL>, greater<LL>>
#define PB push_back
#define POB pop_back
#define PF push_front
#define POF pop_front
#define EB emplace_back
#define MP make_pair
#define TS to_string
#define TU to_ullong
#define BPL __builtin_popcountll
#define FOR(i, a, n) for (i = a; i < n; ++i)
#define FORR(i, a, n) for (i = n - 1; i >= a; --i)
#define rep(i, n) FOR(i, 0, n)
#define repr(i, n) FORR(i, 0, n)
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define SORT(a) sort(ALL(a))
#define REV(a) reverse(ALL(a))
#define UB(a, n) *upper_bound(ALL(a), n)
#define UBn(a, n) upper_bound(ALL(a), n) - a.begin()
#define LB(a, n) *lower_bound(ALL(a), n)
#define LBn(a, n) lower_bound(ALL(a), n) - a.begin()
#define INF 1145141919810364364LL
#define PI 3.14159265358979
#define MOD 1000000007
// #define MOD 998244353
#define ERR 0.00000001
#define FAST                                                                   \\
  cin.tie(0);                                                                  \\
  ios::sync_with_stdio(false)

void Yn(LL a) {
  if (a)
    printf("Yes\\n");
  else
    printf("No\\n");
}
void YN(LL a) {
  if (a)
    printf("YES\\n");
  else
    printf("NO\\n");
}
LL pwmn(LL a, LL n) {
  LL ans = 1;
  while (ans < a)
    ans *= n;
  return ans;
}
LL dig(LL n) {
  LL ret = 0;
  while (n)
    n /= 10, ret++;
  return ret;
}
LL GCD(LL a, LL b) {
  LL c = 1, tmp = max(a, b);
  b = min(a, b);
  a = tmp;
  while (c != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
LL LCM(LL a, LL b) { return a * b / GCD(a, b); }
int lcmp(const void *a, const void *b) {
  if (*(LL *)a > *(LL *)b)
    return 1;
  if (*(LL *)a < *(LL *)b)
    return -1;
  return 0;
}
int lcmpr(const void *a, const void *b) {
  if (*(LL *)a > *(LL *)b)
    return -1;
  if (*(LL *)a < *(LL *)b)
    return 1;
  return 0;
}
int ccmp(const void *a, const void *b) { return *(char *)a - *(char *)b; }
int ccmpr(const void *a, const void *b) { return *(char *)b - *(char *)a; }
int scmp(const void *a, const void *b) { return strcmp((char *)a, (char *)b); }
int scmpr(const void *a, const void *b) { return strcmp((char *)b, (char *)a); }
LL cmod(LL a, LL m) {
  if (a % m < 0)
    return a % m + abs(m);
  else
    return a % m;
}
LL DIV(LL a, LL d, LL m) {
  LL l = m, x = 1, y = 0, k;
  while (l) {
    k = d / l;
    d -= k * l;
    swap(l, d);
    x -= k * y;
    swap(x, y);
  }
  return cmod(a * cmod(x, m), m);
}
LL POW(LL a, LL n, LL m) {
  LL ans = 1;
  while (n > 0) {
    if (n & 1)
      ans = ans * a % m;
    a = a * a % m;
    n >>= 1;
  }
  return ans;
}
VL fact, finv, inv;
void comi(LL n) {
  LL i;
  fact.resize(max(2LL, n + 1));
  finv.resize(max(2LL, n + 1));
  inv.resize(max(2LL, n + 1));
  fact[0] = fact[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  FOR(i, 2, n + 1) {
    fact[i] = fact[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
LL com(LL n, LL k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  return fact[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
bool cmps(pair<LL, LL> a, pair<LL, LL> b) {
  if (a.second != b.second)
    return a.second < b.second;
  return a.first < b.first;
}
template <typename T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

LL H, W, K, x_1, y_1, x_2, y_2;
VVL d;
queue<PA> q;
void BFS() {
  PA p = q.front();
  q.pop();
  LL i, x = p.first, y = p.second;
  // cout<<x<<" "<<y<<endl;
  FOR(i, 1, K + 1) {
    if (x + i >= H || d[x + i][y] <= d[x][y])
      break;
    if (d[x + i][y] == d[x][y] + 1)
      continue;
    d[x + i][y] = d[x][y] + 1;
    q.push(MP(x + i, y));
    if (x + i == x_2 && y == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    if (x - i < 0 || d[x - i][y] <= d[x][y])
      break;
    if (d[x - i][y] == d[x][y] + 1)
      continue;
    d[x - i][y] = d[x][y] + 1;
    q.push(MP(x - i, y));
    if (x - i == x_2 && y == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    if (y + i >= W || d[x][y + i] <= d[x][y])
      break;
    if (d[x][y + i] == d[x][y] + 1)
      continue;
    d[x][y + i] = d[x][y] + 1;
    q.push(MP(x, y + i));
    if (x == x_2 && y + i == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    // cout<<x<<" "<<y-i<<endl;
    // cout<<d[x][y]<<endl;
    if (y - i < 0 || d[x][y - i] <= d[x][y])
      break;
    if (d[x][y - i] == d[x][y] + 1)
      continue;
    d[x][y - i] = d[x][y] + 1;
    q.push(MP(x, y - i));
    // cout<<"!"<<endl;
    if (x == x_2 && y - i == y_2)
      while (!q.empty())
        q.pop();
  }
}

int main() {
  FAST;
  LL i, j;
  cin >> H >> W >> K >> x_1 >> y_1 >> x_2 >> y_2;
  ST c[H];
  rep(i, H) cin >> c[i];
  d.resize(H);
  rep(i, H) d[i].resize(W, INF);
  rep(i, H) rep(j, W) if (c[i][j] == '@') d[i][j] = -1;
  x_1--, y_1--, x_2--, y_2--;
  d[x_1][y_1] = 0;
  q.push(MP(x_1, y_1));
  // cout<<"!"<<endl;
  while (!q.empty())
    BFS();
  if (d[x_2][y_2] == INF)
    d[x_2][y_2] = -1;
  cout << d[x_2][y_2] << endl;
}


Error: TLE

Fixed submission:

#pragma GCC target("avx")
// #pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define DB double
#define LD long double
#define ST string
#define BS bitset
#define PA pair<LL, LL>
#define VE vector
#define VL vector<LL>
#define VP vector<pair<LL, LL>>
#define VVL vector<vector<LL>>
#define PQ priority_queue
#define PQS priority_queue<LL, vector<LL>, greater<LL>>
#define PB push_back
#define POB pop_back
#define PF push_front
#define POF pop_front
#define EB emplace_back
#define MP make_pair
#define TS to_string
#define TU to_ullong
#define BPL __builtin_popcountll
#define FOR(i, a, n) for (i = a; i < n; ++i)
#define FORR(i, a, n) for (i = n - 1; i >= a; --i)
#define rep(i, n) FOR(i, 0, n)
#define repr(i, n) FORR(i, 0, n)
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define SORT(a) sort(ALL(a))
#define REV(a) reverse(ALL(a))
#define UB(a, n) *upper_bound(ALL(a), n)
#define UBn(a, n) upper_bound(ALL(a), n) - a.begin()
#define LB(a, n) *lower_bound(ALL(a), n)
#define LBn(a, n) lower_bound(ALL(a), n) - a.begin()
#define INF 1145141919810364364LL
#define PI 3.14159265358979
#define MOD 1000000007
// #define MOD 998244353
#define ERR 0.00000001
#define FAST                                                                   \\
  cin.tie(0);                                                                  \\
  ios::sync_with_stdio(false)

void Yn(LL a) {
  if (a)
    printf("Yes\\n");
  else
    printf("No\\n");
}
void YN(LL a) {
  if (a)
    printf("YES\\n");
  else
    printf("NO\\n");
}
LL pwmn(LL a, LL n) {
  LL ans = 1;
  while (ans < a)
    ans *= n;
  return ans;
}
LL dig(LL n) {
  LL ret = 0;
  while (n)
    n /= 10, ret++;
  return ret;
}
LL GCD(LL a, LL b) {
  LL c = 1, tmp = max(a, b);
  b = min(a, b);
  a = tmp;
  while (c != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
LL LCM(LL a, LL b) { return a * b / GCD(a, b); }
int lcmp(const void *a, const void *b) {
  if (*(LL *)a > *(LL *)b)
    return 1;
  if (*(LL *)a < *(LL *)b)
    return -1;
  return 0;
}
int lcmpr(const void *a, const void *b) {
  if (*(LL *)a > *(LL *)b)
    return -1;
  if (*(LL *)a < *(LL *)b)
    return 1;
  return 0;
}
int ccmp(const void *a, const void *b) { return *(char *)a - *(char *)b; }
int ccmpr(const void *a, const void *b) { return *(char *)b - *(char *)a; }
int scmp(const void *a, const void *b) { return strcmp((char *)a, (char *)b); }
int scmpr(const void *a, const void *b) { return strcmp((char *)b, (char *)a); }
LL cmod(LL a, LL m) {
  if (a % m < 0)
    return a % m + abs(m);
  else
    return a % m;
}
LL DIV(LL a, LL d, LL m) {
  LL l = m, x = 1, y = 0, k;
  while (l) {
    k = d / l;
    d -= k * l;
    swap(l, d);
    x -= k * y;
    swap(x, y);
  }
  return cmod(a * cmod(x, m), m);
}
LL POW(LL a, LL n, LL m) {
  LL ans = 1;
  while (n > 0) {
    if (n & 1)
      ans = ans * a % m;
    a = a * a % m;
    n >>= 1;
  }
  return ans;
}
VL fact, finv, inv;
void comi(LL n) {
  LL i;
  fact.resize(max(2LL, n + 1));
  finv.resize(max(2LL, n + 1));
  inv.resize(max(2LL, n + 1));
  fact[0] = fact[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  FOR(i, 2, n + 1) {
    fact[i] = fact[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
LL com(LL n, LL k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  return fact[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
bool cmps(pair<LL, LL> a, pair<LL, LL> b) {
  if (a.second != b.second)
    return a.second < b.second;
  return a.first < b.first;
}
template <typename T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

LL H, W, K, x_1, y_1, x_2, y_2;
VVL d;
queue<PA> q;
void BFS() {
  PA p = q.front();
  q.pop();
  LL i, x = p.first, y = p.second;
  // cout<<x<<" "<<y<<endl;
  FOR(i, 1, K + 1) {
    if (x + i >= H || d[x + i][y] < d[x][y])
      break;
    if (d[x + i][y] == d[x][y])
      continue;
    d[x + i][y] = d[x][y] + 1;
    q.push(MP(x + i, y));
    if (x + i == x_2 && y == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    if (x - i < 0 || d[x - i][y] < d[x][y])
      break;
    if (d[x - i][y] == d[x][y])
      continue;
    d[x - i][y] = d[x][y] + 1;
    q.push(MP(x - i, y));
    if (x - i == x_2 && y == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    if (y + i >= W || d[x][y + i] < d[x][y])
      break;
    if (d[x][y + i] == d[x][y])
      continue;
    d[x][y + i] = d[x][y] + 1;
    q.push(MP(x, y + i));
    if (x == x_2 && y + i == y_2)
      while (!q.empty())
        q.pop();
  }
  FOR(i, 1, K + 1) {
    // cout<<x<<" "<<y-i<<endl;
    // cout<<d[x][y]<<endl;
    if (y - i < 0 || d[x][y - i] < d[x][y])
      break;
    if (d[x][y - i] == d[x][y])
      continue;
    d[x][y - i] = d[x][y] + 1;
    q.push(MP(x, y - i));
    // cout<<"!"<<endl;
    if (x == x_2 && y - i == y_2)
      while (!q.empty())
        q.pop();
  }
}

int main() {
  FAST;
  LL i, j;
  cin >> H >> W >> K >> x_1 >> y_1 >> x_2 >> y_2;
  ST c[H];
  rep(i, H) cin >> c[i];
  d.resize(H);
  rep(i, H) d[i].resize(W, INF);
  rep(i, H) rep(j, W) if (c[i][j] == '@') d[i][j] = -1;
  x_1--, y_1--, x_2--, y_2--;
  d[x_1][y_1] = 0;
  q.push(MP(x_1, y_1));
  // cout<<"!"<<endl;
  while (!q.empty())
    BFS();
  if (d[x_2][y_2] == INF)
    d[x_2][y_2] = -1;
  cout << d[x_2][y_2] << endl;
}