Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

#define FAST                                                                   \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL)
#define pf printf
#define sc scanf

#define sf(n) scanf("%d", &n)
#define sff(n1, n2) scanf("%d %d", &n1, &n2)
#define sfff(n1, n2, n3) scanf("%d %d %d", &n1, &n2, &n3)
#define sl(n) scanf("%lld", &n)
#define sll(n1, n2) scanf("%lld %lld", &n1, &n2)
#define slll(n1, n2, n3) scanf("%lld %lld %lld", &n1, &n2, &n3)

#define rep0(i, n) for (i = 0; i < n; i++)
#define rep(i, n) for (i = 1; i <= n; i++)
#define reps(i, a, n) for (i = a; i <= n; i++)

#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sq(x) ((x) * (x))
#define sz(x) x.size()

#define mem(ara, n) memset(ara, n, sizeof(ara))
#define memb(ara) memset(ara, false, sizeof(ara))

#define pi pair<int, int>
#define pii pair<pair<int, int>, pair<int, int>>

#define endl "\n";
#define line puts("-------");
#define dbb(x) cout << #x << " : " << x << "\n";

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const queue<T> &x) {
  queue<T> temp = x;
  cerr << "\n-----\n";
  while (!temp.empty()) {
    cerr << temp.front() << endl;
    temp.pop();
  }
  cerr << "-----\n";
}
template <typename T> void __print(const stack<T> &x) {
  stack<T> temp = x;
  cerr << "\n-----\n";
  while (!temp.empty()) {
    cerr << temp.top() << endl;
    temp.pop();
  }
  cerr << "-----\n";
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}

#ifndef ONLINE_JUDGE
#define db(x...) cerr << "[" << #x << "] = [", _print(x)
#endif
using ll = long long;
const int N = 100005;
const int MOD = 1000000007;
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
int p, q, pp, qq, n, m, k;
string a[N];
bool valid(int x, int y) {
  if (x >= 0 && x < n && y >= 0 && y < m && a[x][y] == '.')
    return true;
  return false;
}
int main() {
#ifndef ONLINE_JUDGE
  // freopen("input.txt", "r", stdin);
  // freopen("output.txt","w",stdout);
#endif
  FAST;
  cin >> n >> m >> k >> p >> q >> pp >> qq;
  cin.ignore();
  int i, j;
  rep0(i, n) cin >> a[i];
  if (p == pp && q == qq) {
    cout << 0;
    return 0;
  }
  bool vis[n + 1][m + 1];
  int cost[n + 1][m + 1];
  rep0(i, n + 1) {
    rep0(j, m + 1) {
      vis[i][j] = false;
      cost[i][j] = 0;
    }
  }
  p--;
  q--;
  pp--;
  qq--;
  vis[p][q] = true;
  cost[p][q] = 0;
  queue<pi> qqq;
  qqq.push({p, q});
  while (!qqq.empty()) {
    pi pr = qqq.front();
    int x = pr.fi, y = pr.se;
    if (x == pp && y == qq) {
      cout << cost[pp][qq];
      return 0;
    }
    qqq.pop();
    rep0(i, 4) {
      rep(j, k) {
        int xx = x + dx[i] * j;
        int yy = y + dy[i] * j;
        if (!valid(xx, yy))
          break;
        if (!vis[xx][yy]) {
          vis[xx][yy] = true;
          cost[xx][yy] = cost[x][y] + 1;
          if (xx == pp && yy == qq) {
            cout << cost[pp][qq];
            return 0;
          }
          qqq.push({xx, yy});
        }
      }
    }
  }
  cout << -1;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;

#define FAST                                                                   \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL)
#define pf printf
#define sc scanf

#define sf(n) scanf("%d", &n)
#define sff(n1, n2) scanf("%d %d", &n1, &n2)
#define sfff(n1, n2, n3) scanf("%d %d %d", &n1, &n2, &n3)
#define sl(n) scanf("%lld", &n)
#define sll(n1, n2) scanf("%lld %lld", &n1, &n2)
#define slll(n1, n2, n3) scanf("%lld %lld %lld", &n1, &n2, &n3)

#define rep0(i, n) for (i = 0; i < n; i++)
#define rep(i, n) for (i = 1; i <= n; i++)
#define reps(i, a, n) for (i = a; i <= n; i++)

#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sq(x) ((x) * (x))
#define sz(x) x.size()

#define mem(ara, n) memset(ara, n, sizeof(ara))
#define memb(ara) memset(ara, false, sizeof(ara))

#define pi pair<int, int>
#define pii pair<pair<int, int>, pair<int, int>>

#define endl "\n";
#define line puts("-------");
#define dbb(x) cout << #x << " : " << x << "\n";

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const queue<T> &x) {
  queue<T> temp = x;
  cerr << "\n-----\n";
  while (!temp.empty()) {
    cerr << temp.front() << endl;
    temp.pop();
  }
  cerr << "-----\n";
}
template <typename T> void __print(const stack<T> &x) {
  stack<T> temp = x;
  cerr << "\n-----\n";
  while (!temp.empty()) {
    cerr << temp.top() << endl;
    temp.pop();
  }
  cerr << "-----\n";
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}

#ifndef ONLINE_JUDGE
#define db(x...) cerr << "[" << #x << "] = [", _print(x)
#endif
using ll = long long;
const int N = 100005;
const int MOD = 1000000007;
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
int p, q, pp, qq, n, m, k;
string a[N];
bool valid(int x, int y) {
  if (x >= 0 && x < n && y >= 0 && y < m && a[x][y] == '.')
    return true;
  return false;
}
int main() {
#ifndef ONLINE_JUDGE
  // freopen("input.txt", "r", stdin);
  // freopen("output.txt","w",stdout);
#endif
  FAST;
  cin >> n >> m >> k >> p >> q >> pp >> qq;
  cin.ignore();
  int i, j;
  rep0(i, n) cin >> a[i];
  if (p == pp && q == qq) {
    cout << 0;
    return 0;
  }
  bool vis[n + 1][m + 1];
  int cost[n + 1][m + 1];
  rep0(i, n + 1) {
    rep0(j, m + 1) {
      vis[i][j] = false;
      cost[i][j] = 0;
    }
  }
  p--;
  q--;
  pp--;
  qq--;
  vis[p][q] = true;
  cost[p][q] = 0;
  queue<pi> qqq;
  qqq.push({p, q});
  while (!qqq.empty()) {
    pi pr = qqq.front();
    int x = pr.fi, y = pr.se;
    if (x == pp && y == qq) {
      cout << cost[pp][qq];
      return 0;
    }
    qqq.pop();
    rep0(i, 4) {
      rep(j, k) {
        int xx = x + dx[i] * j;
        int yy = y + dy[i] * j;
        if (!valid(xx, yy))
          break;
        if (!vis[xx][yy]) {
          vis[xx][yy] = true;
          cost[xx][yy] = cost[x][y] + 1;
          if (xx == pp && yy == qq) {
            cout << cost[pp][qq];
            return 0;
          }
          qqq.push({xx, yy});
        } else {
          if (cost[xx][yy] >= cost[x][y] + 1)
            cost[xx][yy] = cost[x][y] + 1;
          else
            break;
        }
      }
    }
  }
  cout << -1;
}