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

#include <algorithm>
#include <iostream>
#include <queue>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rep1(i, n) for (int i = 1; i <= n; ++i)
using namespace std;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int main() {
  int h, w, k;
  cin >> h >> w >> k;
  vector<int> s(4);
  rep(i, 4) {
    cin >> s[i];
    s[i]--;
  }
  vector<vector<char>> c(h, vector<char>(w));
  rep(i, h) rep(j, w) cin >> c[i][j];

  using pi = pair<int, int>;
  using pii = pair<int, pi>;
  queue<pii> q;
  q.push({0, {s[0], s[1]}});
  vector<vector<int>> d(h, vector<int>(w, -1));
  d[s[0]][s[1]] = 0;
  vector<int> dx = {1, 0, -1, 0};
  vector<int> dy = {0, 1, 0, -1};
  while (!q.empty()) {
    pii p = q.front();
    q.pop();
    int dd = p.first;
    int x = p.second.first, y = p.second.second;
    rep(i, 4) {
      rep1(j, k) {
        int nx = x + dx[i] * j;
        int ny = y + dy[i] * j;
        if (0 <= nx && nx < h && 0 <= ny && ny < w) {
          if (c[nx][ny] == '@')
            break;
          if (d[nx][ny] == d[x][y] + 1)
            continue;
          if (0 <= d[nx][ny])
            break;
          d[nx][ny] = d[x][y] + 1;
          q.push({d[nx][ny], {nx, ny}});
        } else
          break;
      }
    }
  }

  // rep(i,h) {
  //   rep(j,w) cout << d[i][j] << " ";
  //   cout << "\\n";
  // }

  cout << d[s[2]][s[3]] << "\\n";

  return 0;
}


Error: TLE

Fixed submission:

#include <algorithm>
#include <iostream>
#include <queue>
#include <utility>
#include <vector>
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rep1(i, n) for (int i = 1; i <= n; ++i)
using namespace std;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int main() {
  int h, w, k;
  cin >> h >> w >> k;
  vector<int> s(4);
  rep(i, 4) {
    cin >> s[i];
    s[i]--;
  }
  vector<vector<char>> c(h, vector<char>(w));
  rep(i, h) rep(j, w) cin >> c[i][j];

  using pi = pair<int, int>;
  using pii = pair<int, pi>;
  queue<pii> q;
  q.push({0, {s[0], s[1]}});
  vector<vector<int>> d(h, vector<int>(w, -1));
  d[s[0]][s[1]] = 0;
  vector<int> dx = {1, 0, -1, 0};
  vector<int> dy = {0, 1, 0, -1};
  while (!q.empty()) {
    pii p = q.front();
    q.pop();
    int dd = p.first;
    int x = p.second.first, y = p.second.second;
    rep(i, 4) {
      rep1(j, k) {
        int nx = x + dx[i] * j;
        int ny = y + dy[i] * j;
        if (0 <= nx && nx < h && 0 <= ny && ny < w) {
          if (c[nx][ny] == '@')
            break;
          if (0 <= d[nx][ny] && d[nx][ny] <= d[x][y])
            break;
          d[nx][ny] = d[x][y] + 1;
          q.push({d[nx][ny], {nx, ny}});
        } else
          break;
      }
    }
  }

  // rep(i,h) {
  //   rep(j,w) cout << d[i][j] << " ";
  //   cout << "\\n";
  // }

  cout << d[s[2]][s[3]] << "\\n";

  return 0;
}