Problem p02644 (C++)

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

#define FOR(i, a, b) for (auto i = a; i <= b; ++i)
#define REP(i, a, b) for (auto i = a; i < b; ++i)
#define FORI(i, a, b)                                                          \
  for (auto i = a; i != b + 1 - 2 * (a > b); i += 1 - 2 * (a > b))
#define REPI(i, a, b)                                                          \
  for (auto i = a - (a > b); i != b - (a > b); i += 1 - 2 * (a > b))
#define ALL(v) v.begin(), v.end()
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define pf(a) push_front(a)
#define eb(a, b) emplace_back(a, b)
#define fir first
#define sec second
#define what_is(x) cout << #x << " is " << x << endl;
#define type(x) typeid(x).name()
#define ms(arr, val) memset(arr, val, sizeof(arr))
#define min3(a, b, c) min(min(a, b), c)
#define max3(a, b, c) max(max(a, b), c)
#define PI acos(-1)
#define open_read freopen("christmas.in", "r", stdin)
#define open_write freopen("christmas.out", "w", stdout)

using namespace std;

typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
typedef pair<double, double> PDD;
typedef pair<int, int> PII;
typedef pair<int, PII> PIPII;
typedef pair<PII, PII> PPIIPII;
typedef pair<LL, LL> PLL;
typedef pair<ULL, ULL> PUU;
typedef pair<LL, PLL> PLPLL;
typedef pair<PLL, PLL> PPLLPLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;

template <typename T, typename T1>
ostream &operator<<(ostream &out, pair<T, T1> obj) {
  out << "(" << obj.first << ", " << obj.second << ")";
  return out;
}

template <typename T, typename T1>
ostream &operator<<(ostream &out, map<T, T1> cont) {
  typename map<T, T1>::const_iterator itr = cont.begin();
  typename map<T, T1>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T> ostream &operator<<(ostream &out, set<T> cont) {
  typename set<T>::const_iterator itr = cont.begin();
  typename set<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T> ostream &operator<<(ostream &out, multiset<T> cont) {
  typename multiset<T>::const_iterator itr = cont.begin();
  typename multiset<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T,
          template <typename ELEM, typename ALLOC = allocator<ELEM>> class CONT>
ostream &operator<<(ostream &out, CONT<T> cont) {
  typename CONT<T>::const_iterator itr = cont.begin();
  typename CONT<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T, unsigned int N, typename CTy, typename CTr>
typename enable_if<!is_same<T, char>::value, basic_ostream<CTy, CTr> &>::type
operator<<(basic_ostream<CTy, CTr> &out, const T (&arr)[N]) {
  REP(i, 0, N) { out << arr[i] << " "; }

  out << endl;
  return out;
}

template <typename T> T GCD(T a, T b) {
  T min_v = min(a, b);
  T max_v = max(a, b);

  while (min_v) {
    T temp = max_v % min_v;
    max_v = min_v;
    min_v = temp;
  }

  return max_v;
}

template <typename T> T LCM(T a, T b) { return (a * b) / gcd(a, b); }

template <typename T> T fastExpPow(T base, T exp, T mod) {
  T res = 1;

  while (exp) {
    if (exp & 1) {
      res *= base;
      res %= mod;
    }

    exp >>= 1;
    base *= base;
    base %= mod;
  }

  return res % mod;
}

/*#################################################################################################################
###################################################################################################################
###################################################################################################################
#################################################################################################################*/

#define SIZE 1000010

int H, W, K, X1, Y1, X2, Y2;
vector<char> board[SIZE];
map<PIPII, int> minDist;
queue<PIPII> que;

bool invalid(PII pos) {
  return pos.fir >= H || pos.fir < 0 || pos.sec >= W || pos.sec < 0 ||
         board[pos.fir][pos.sec] == '@';
}

void bfs() {
  que.push(mp(0, mp(X1, Y1)));
  que.push(mp(1, mp(X1, Y1)));
  minDist[mp(0, mp(X1, Y1))] = 0;
  minDist[mp(1, mp(X1, Y1))] = 0;

  while (!que.empty()) {
    int type = que.front().fir;
    PII pos = que.front().sec;
    que.pop();

    int currDist = minDist[mp(type, pos)];

    FOR(t, 0, 1) {
      for (int dir = -1; dir <= 1; dir += 2) {
        FOR(i, 1, K) {
          PII newPos = mp(pos.fir + i * dir * (int)(t == 0),
                          pos.sec + i * dir * (int)(t == 1));

          if ((minDist.count(mp(t, newPos)) &&
               minDist[mp(t, newPos)] < currDist + 1) ||
              invalid(newPos)) {
            break;
          }

          minDist[mp(t, newPos)] = currDist + 1;
          que.push(mp(t, newPos));
        }
      }
    }
  }
}

int main() {
  scanf("%d%d%d%d%d%d%d", &H, &W, &K, &X1, &Y1, &X2, &Y2);
  --X1, --Y1, --X2, --Y2;

  REP(i, 0, H) {
    REP(j, 0, W) {
      char ch;
      scanf(" %c", &ch);
      board[i].pb(ch);
    }
  }

  bfs();
  int answer = -1;

  FOR(t, 0, 1) {
    if (minDist.count(mp(t, mp(X2, Y2)))) {
      answer = (answer == -1 ? minDist[mp(t, mp(X2, Y2))]
                             : min(answer, minDist[mp(t, mp(X2, Y2))]));
    }
  }

  printf("%d\n", answer);
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

#define FOR(i, a, b) for (auto i = a; i <= b; ++i)
#define REP(i, a, b) for (auto i = a; i < b; ++i)
#define FORI(i, a, b)                                                          \
  for (auto i = a; i != b + 1 - 2 * (a > b); i += 1 - 2 * (a > b))
#define REPI(i, a, b)                                                          \
  for (auto i = a - (a > b); i != b - (a > b); i += 1 - 2 * (a > b))
#define ALL(v) v.begin(), v.end()
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define pf(a) push_front(a)
#define eb(a, b) emplace_back(a, b)
#define fir first
#define sec second
#define what_is(x) cout << #x << " is " << x << endl;
#define type(x) typeid(x).name()
#define ms(arr, val) memset(arr, val, sizeof(arr))
#define min3(a, b, c) min(min(a, b), c)
#define max3(a, b, c) max(max(a, b), c)
#define PI acos(-1)
#define open_read freopen("christmas.in", "r", stdin)
#define open_write freopen("christmas.out", "w", stdout)

using namespace std;

typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
typedef pair<double, double> PDD;
typedef pair<int, int> PII;
typedef pair<int, PII> PIPII;
typedef pair<PII, PII> PPIIPII;
typedef pair<LL, LL> PLL;
typedef pair<ULL, ULL> PUU;
typedef pair<LL, PLL> PLPLL;
typedef pair<PLL, PLL> PPLLPLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;

template <typename T, typename T1>
ostream &operator<<(ostream &out, pair<T, T1> obj) {
  out << "(" << obj.first << ", " << obj.second << ")";
  return out;
}

template <typename T, typename T1>
ostream &operator<<(ostream &out, map<T, T1> cont) {
  typename map<T, T1>::const_iterator itr = cont.begin();
  typename map<T, T1>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T> ostream &operator<<(ostream &out, set<T> cont) {
  typename set<T>::const_iterator itr = cont.begin();
  typename set<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T> ostream &operator<<(ostream &out, multiset<T> cont) {
  typename multiset<T>::const_iterator itr = cont.begin();
  typename multiset<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T,
          template <typename ELEM, typename ALLOC = allocator<ELEM>> class CONT>
ostream &operator<<(ostream &out, CONT<T> cont) {
  typename CONT<T>::const_iterator itr = cont.begin();
  typename CONT<T>::const_iterator ends = cont.end();

  for (; itr != ends; ++itr) {
    out << *itr << " ";
  }

  out << endl;
  return out;
}

template <typename T, unsigned int N, typename CTy, typename CTr>
typename enable_if<!is_same<T, char>::value, basic_ostream<CTy, CTr> &>::type
operator<<(basic_ostream<CTy, CTr> &out, const T (&arr)[N]) {
  REP(i, 0, N) { out << arr[i] << " "; }

  out << endl;
  return out;
}

template <typename T> T GCD(T a, T b) {
  T min_v = min(a, b);
  T max_v = max(a, b);

  while (min_v) {
    T temp = max_v % min_v;
    max_v = min_v;
    min_v = temp;
  }

  return max_v;
}

template <typename T> T LCM(T a, T b) { return (a * b) / gcd(a, b); }

template <typename T> T fastExpPow(T base, T exp, T mod) {
  T res = 1;

  while (exp) {
    if (exp & 1) {
      res *= base;
      res %= mod;
    }

    exp >>= 1;
    base *= base;
    base %= mod;
  }

  return res % mod;
}

/*#################################################################################################################
###################################################################################################################
###################################################################################################################
#################################################################################################################*/

#define SIZE 1000010

int H, W, K, X1, Y1, X2, Y2;
vector<char> board[SIZE];
map<PIPII, int> minDist;
queue<PIPII> que;

bool invalid(PII pos) {
  return pos.fir >= H || pos.fir < 0 || pos.sec >= W || pos.sec < 0 ||
         board[pos.fir][pos.sec] == '@';
}

void bfs() {
  que.push(mp(0, mp(X1, Y1)));
  que.push(mp(1, mp(X1, Y1)));
  minDist[mp(0, mp(X1, Y1))] = 0;
  minDist[mp(1, mp(X1, Y1))] = 0;

  while (!que.empty()) {
    int type = que.front().fir;
    PII pos = que.front().sec;
    que.pop();

    int currDist = minDist[mp(type, pos)];

    FOR(t, 0, 1) {
      for (int dir = -1; dir <= 1; dir += 2) {
        FOR(i, 1, K) {
          PII newPos = mp(pos.fir + i * dir * (int)(t == 0),
                          pos.sec + i * dir * (int)(t == 1));

          if (minDist.count(mp(t, newPos)) || invalid(newPos)) {
            break;
          }

          if (minDist.count(mp(1 - t, newPos)) &&
              minDist[mp(1 - t, newPos)] <= currDist) {
            break;
          }

          minDist[mp(t, newPos)] = currDist + 1;
          que.push(mp(t, newPos));
        }
      }
    }
  }
}

int main() {
  scanf("%d%d%d%d%d%d%d", &H, &W, &K, &X1, &Y1, &X2, &Y2);
  --X1, --Y1, --X2, --Y2;

  REP(i, 0, H) {
    REP(j, 0, W) {
      char ch;
      scanf(" %c", &ch);
      board[i].pb(ch);
    }
  }

  bfs();
  int answer = -1;

  FOR(t, 0, 1) {
    if (minDist.count(mp(t, mp(X2, Y2)))) {
      answer = (answer == -1 ? minDist[mp(t, mp(X2, Y2))]
                             : min(answer, minDist[mp(t, mp(X2, Y2))]));
    }
  }

  printf("%d\n", answer);
  return 0;
}