Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma GCC optimize("O3")
#include "bits/stdc++.h"

using namespace std;
using ll = long long int;

#define all(v) (v).begin(), (v).end()
#define repeat(cnt, l)                                                         \
  for (typename remove_const<                                                  \
           typename remove_reference<decltype(l)>::type>::type cnt = {};       \
       (cnt) < (l); ++(cnt))
#define rrepeat(cnt, l) for (auto cnt = (l)-1; 0 <= (cnt); --(cnt))
#define iterate(cnt, b, e) for (auto cnt = (b); (cnt) != (e); ++(cnt))
#define diterate(cnt, b, e) for (auto cnt = (b); (cnt) != (e); --(cnt))
const long long MD = 1000000007ll;
const long double PI = 3.1415926535897932384626433832795L;
template <typename T1, typename T2>
inline ostream &operator<<(ostream &o, const pair<T1, T2> p) {
  o << '(' << p.first << ':' << p.second << ')';
  return o;
}
template <typename T> inline T &chmax(T &to, const T &val) {
  return to = max(to, val);
}
template <typename T> inline T &chmin(T &to, const T &val) {
  return to = min(to, val);
}
void bye(string s, int code = 0) {
  cout << s << endl;
  exit(code);
}
mt19937_64 randdev(8901016);
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_integral<T>::value>::type * = nullptr>
inline T rand(T l, T h, Random &rand = randdev) {
  return uniform_int_distribution<T>(l, h)(rand);
}
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_floating_point<T>::value>::type * = nullptr>
inline T rand(T l, T h, Random &rand = randdev) {
  return uniform_real_distribution<T>(l, h)(rand);
}

template <typename I> struct MyRangeFormat {
  I b, e;
  MyRangeFormat(I _b, I _e) : b(_b), e(_e) {}
};
template <typename I>
static ostream &operator<<(ostream &o, const MyRangeFormat<I> &f) {
  o << "[ ";
  iterate(i, f.b, f.e) o << *i << ' ';
  return o << ']';
}
template <typename I> struct MyMatrixFormat {
  const I &p;
  long long n, m;
  MyMatrixFormat(const I &_p, long long _n, long long _m)
      : p(_p), n(_n), m(_m) {}
};
template <typename I>
static ostream &operator<<(ostream &o, const MyMatrixFormat<I> &f) {
  o << '\n';
  repeat(i, (f.n)) {
    repeat(j, f.m) o << f.p[i][j] << ' ';
    o << '\n';
  }
  return o;
}
struct LOG_t {
  ~LOG_t() { cout << endl; }
};
#define LOG (LOG_t(), cout << 'L' << __LINE__ << ": ")
#define FMTA(m, w) (MyRangeFormat<decltype(m + 0)>(m, m + w))
#define FMTR(b, e) (MyRangeFormat<decltype(e)>(b, e))
#define FMTV(v) FMTR(v.begin(), v.end())
#define FMTM(m, h, w) (MyMatrixFormat<decltype(m + 0)>(m, h, w))

#if defined(_WIN32) || defined(_WIN64)
#define getc_x _getc_nolock
#define putc_x _putc_nolock
#elif defined(__GNUC__)
#define getc_x getc_unlocked
#define putc_x putc_unlocked
#else
#define getc_x getc
#define putc_x putc
#endif
class MaiScanner {
  FILE *fp_;
  constexpr bool isvisiblechar(char c) noexcept {
    return (0x21 <= (c) && (c) <= 0x7E);
  }

public:
  inline MaiScanner(FILE *fp) : fp_(fp) {}
  template <typename T> void input_integer(T &var) noexcept {
    var = 0;
    T sign = 1;
    int cc = getc_x(fp_);
    for (; cc < '0' || '9' < cc; cc = getc_x(fp_))
      if (cc == '-')
        sign = -1;
    for (; '0' <= cc && cc <= '9'; cc = getc_x(fp_))
      var = (var << 3) + (var << 1) + cc - '0';
    var = var * sign;
  }
  inline int c() noexcept { return getc_x(fp_); }
  template <typename T, typename enable_if<is_integral<T>::value,
                                           nullptr_t>::type = nullptr>
  inline MaiScanner &operator>>(T &var) noexcept {
    input_integer<T>(var);
    return *this;
  }
  inline MaiScanner &operator>>(string &var) {
    int cc = getc_x(fp_);
    for (; !isvisiblechar(cc); cc = getc_x(fp_))
      ;
    for (; isvisiblechar(cc); cc = getc_x(fp_))
      var.push_back(cc);
    return *this;
  }
  template <typename IT> inline void in(IT begin, IT end) {
    for (auto it = begin; it != end; ++it)
      *this >> *it;
  }
};
class MaiPrinter {
  FILE *fp_;

public:
  inline MaiPrinter(FILE *fp) : fp_(fp) {}
  template <typename T> void output_integer(T var) noexcept {
    if (var == 0) {
      putc_x('0', fp_);
      return;
    }
    if (var < 0)
      putc_x('-', fp_), var = -var;
    char stack[32];
    int stack_p = 0;
    while (var)
      stack[stack_p++] = '0' + (var % 10), var /= 10;
    while (stack_p)
      putc_x(stack[--stack_p], fp_);
  }
  inline MaiPrinter &operator<<(char c) noexcept {
    putc_x(c, fp_);
    return *this;
  }
  template <typename T, typename enable_if<is_integral<T>::value,
                                           nullptr_t>::type = nullptr>
  inline MaiPrinter &operator<<(T var) noexcept {
    output_integer<T>(var);
    return *this;
  }
  inline MaiPrinter &operator<<(char *str_p) noexcept {
    while (*str_p)
      putc_x(*(str_p++), fp_);
    return *this;
  }
  inline MaiPrinter &operator<<(const string &str) {
    const char *p = str.c_str();
    const char *l = p + str.size();
    while (p < l)
      putc_x(*p++, fp_);
    return *this;
  }
  template <typename IT> void join(IT begin, IT end, char sep = ' ') {
    for (bool b = 0; begin != end; ++begin, b = 1)
      b ? *this << sep << *begin : *this << *begin;
  }
};
MaiScanner scanner(stdin);
MaiPrinter printer(stdout);

struct P {
  using T = int;
  T y, x;

  inline explicit P(T _y, T _x) : y(_y), x(_x) {}
  inline P() : y(0), x(0) {}

  inline bool operator==(P p) const { return y == p.y && x == p.x; }
  inline bool operator<(P p) const { return y == p.y ? x < p.x : y < p.y; }
  inline P operator+(P p) const { return P(y + p.y, x + p.x); }
  inline P operator-(P p) const { return P(y - p.y, x - p.x); }
  inline P &operator+=(P p) {
    y += p.y;
    x += p.x;
    return *this;
  }
  inline P &operator-=(P p) {
    y -= p.y;
    x -= p.x;
    return *this;
  }
  inline P &operator-=(T m) {
    y *= m;
    x;
    return *this;
  }
  inline T distM(P p) const { return abs(y - p.y) + abs(x - p.x); }
  inline T distC(P p) const { return max(abs(y - p.y), abs(x - p.x)); }
  template <typename ITR> ITR nearestM(ITR begin, ITR end) const {
    if (begin == end)
      return end;
    T best = distM(*begin);
    ITR besti = begin;
    for (ITR it = begin; ++it, it != end;) {
      T m = distM(*it);
      if (best < m) {
        best = m;
        besti = it;
      }
    }
    return besti;
  }
};
inline ostream &operator<<(ostream &os, P p) {
  os << '(' << p.y << ',' << p.x << ')';
  return os;
}

const P FourMoving[] = {P(-1, 0), P(0, 1), P(1, 0), P(0, -1)};
const P FiveMoving[] = {P(-1, 0), P(0, 1), P(1, 0), P(0, -1), P(0, 0)};
const P EightMoving[] = {P(-1, 0),  P(0, 1),  P(1, 0),  P(0, -1),
                         P(-1, -1), P(-1, 1), P(1, -1), P(1, 1)};

inline P operator*(P::T m, P p) noexcept { return P(m * p.y, m * p.x); }

template <typename T>
// using T = int;
struct F {
  int height, width;
  vector<T> data;

  F(int h = 1, int w = 1) : height(h), width(w), data(h * w) {}

  inline T &operator()(int y, int x) { return data[x + y * width]; }
  inline T &operator()(P p) { return data[p.x + p.y * width]; }
  inline T operator()(int y, int x) const { return data[x + y * width]; }
  inline T operator()(P p) const { return data[p.x + p.y * width]; }

  inline bool safe(int y, int x) const {
    return 0 <= y && y < height && 0 <= x && x < width;
  }
  inline bool safe(P p) const {
    return 0 <= p.y && p.y < height && 0 <= p.x && p.x < width;
  }

  inline void fill(T e) { std::fill(all(data), e); }
  inline void resize(int h, int w) {
    height = h;

    width = w;
    data.resize(h * w);
  }

  void print(ostream &os, int setw_arg = 4) {
    for (int y = 0; y < height; ++y) {
      for (int x = 0; x < width; ++x)
        os << setw(setw_arg) << operator()(y, x) << ' ';
      os << '\n';
    }
  }
};
// Edge構造体を定義する無向グラフ
class GraphE {
public:
  using W_T = int;
  struct Edge {
    int u, v;
    W_T value;
    Edge(int from = 0, int to = 0, W_T value = 0)
        : u(from), v(to), value(value) {}
    inline int to(int _v) const { return _v == v ? u : v; }
  };
  size_t n;
  vector<vector<int>> vertex_to;
  vector<Edge> edges;

  explicit GraphE(int n = 1) : n(n), vertex_to(n) {}

  inline size_t size() const noexcept { return n; }
  void resize(size_t _n) { vertex_to.resize(n = _n); }
  void connect(int from, int to, W_T val = 0) {
    vertex_to[(size_t)from].push_back((int)edges.size());
    vertex_to[(size_t)to].push_back((int)edges.size());
    edges.emplace_back(from, to, val);
  }
  void connect(vector<Edge> &&es) {
    edges = move(es);
    for (int i = 0; (size_t)i < edges.size(); ++i) {
      vertex_to[edges[i].u].push_back(i);
      vertex_to[edges[i].v].push_back(i);
    }
  }
};

//

int H, W, K;
int startx, starty, goalx, goaly;

//

F<int> field;
F<int> dist;
// GraphE graph;

inline int cv(int y, int x) { return y * W + x; }

int main() {
  scanner >> H >> W >> K;
  scanner >> starty >> startx >> goaly >> goalx;
  --startx;
  --starty;
  --goalx;
  --goaly;

  field.resize(H, W);
  // graph.resize(H*W);

  repeat(i, H) {
    string str;
    scanner >> str;
    repeat(j, W) {
      char c = str[j];
      field(i, j) = c == '@';
    }
  }

  dist.resize(H, W);
  dist.fill(1e9);

  queue<P> que;
  que.emplace(starty, startx);
  dist(starty, startx) = 0;
  while (!que.empty()) {
    auto p = que.front();
    que.pop();
    auto d = dist(p);
    if (p == P(goaly, goalx)) {
      cout << d << endl;
      exit(0); // memfree by os
    }
    for (auto v : FourMoving) {
      auto p2 = v + p;
      repeat(i, K) {
        if (!field.safe(p2))
          break;
        if (field(p2))
          break;
        if (dist(p2) < d)
          break;

        if (dist(p2) > d + 1) {
          dist(p2) = d + 1;
          que.push(p2);
        }
        p2 += v;
      }
    }
    // repeat(i, H) {
    //   repeat(j, W) {
    //     cout << min(dist(i,j), 9);
    //   }
    //   cout << endl;
    // }
    // cout << endl;
  }

  cout << "-1" << endl;
  exit(0);

  return 0;
}


Fixed submission:
#pragma GCC optimize("O3")
#include "bits/stdc++.h"

using namespace std;
using ll = long long int;

#define all(v) (v).begin(), (v).end()
#define repeat(cnt, l)                                                         \
  for (typename remove_const<                                                  \
           typename remove_reference<decltype(l)>::type>::type cnt = {};       \
       (cnt) < (l); ++(cnt))
#define rrepeat(cnt, l) for (auto cnt = (l)-1; 0 <= (cnt); --(cnt))
#define iterate(cnt, b, e) for (auto cnt = (b); (cnt) != (e); ++(cnt))
#define diterate(cnt, b, e) for (auto cnt = (b); (cnt) != (e); --(cnt))
const long long MD = 1000000007ll;
const long double PI = 3.1415926535897932384626433832795L;
template <typename T1, typename T2>
inline ostream &operator<<(ostream &o, const pair<T1, T2> p) {
  o << '(' << p.first << ':' << p.second << ')';
  return o;
}
template <typename T> inline T &chmax(T &to, const T &val) {
  return to = max(to, val);
}
template <typename T> inline T &chmin(T &to, const T &val) {
  return to = min(to, val);
}
void bye(string s, int code = 0) {
  cout << s << endl;
  exit(code);
}
mt19937_64 randdev(8901016);
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_integral<T>::value>::type * = nullptr>
inline T rand(T l, T h, Random &rand = randdev) {
  return uniform_int_distribution<T>(l, h)(rand);
}
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_floating_point<T>::value>::type * = nullptr>
inline T rand(T l, T h, Random &rand = randdev) {
  return uniform_real_distribution<T>(l, h)(rand);
}

template <typename I> struct MyRangeFormat {
  I b, e;
  MyRangeFormat(I _b, I _e) : b(_b), e(_e) {}
};
template <typename I>
static ostream &operator<<(ostream &o, const MyRangeFormat<I> &f) {
  o << "[ ";
  iterate(i, f.b, f.e) o << *i << ' ';
  return o << ']';
}
template <typename I> struct MyMatrixFormat {
  const I &p;
  long long n, m;
  MyMatrixFormat(const I &_p, long long _n, long long _m)
      : p(_p), n(_n), m(_m) {}
};
template <typename I>
static ostream &operator<<(ostream &o, const MyMatrixFormat<I> &f) {
  o << '\n';
  repeat(i, (f.n)) {
    repeat(j, f.m) o << f.p[i][j] << ' ';
    o << '\n';
  }
  return o;
}
struct LOG_t {
  ~LOG_t() { cout << endl; }
};
#define LOG (LOG_t(), cout << 'L' << __LINE__ << ": ")
#define FMTA(m, w) (MyRangeFormat<decltype(m + 0)>(m, m + w))
#define FMTR(b, e) (MyRangeFormat<decltype(e)>(b, e))
#define FMTV(v) FMTR(v.begin(), v.end())
#define FMTM(m, h, w) (MyMatrixFormat<decltype(m + 0)>(m, h, w))

#if defined(_WIN32) || defined(_WIN64)
#define getc_x _getc_nolock
#define putc_x _putc_nolock
#elif defined(__GNUC__)
#define getc_x getc_unlocked
#define putc_x putc_unlocked
#else
#define getc_x getc
#define putc_x putc
#endif
class MaiScanner {
  FILE *fp_;
  constexpr bool isvisiblechar(char c) noexcept {
    return (0x21 <= (c) && (c) <= 0x7E);
  }

public:
  inline MaiScanner(FILE *fp) : fp_(fp) {}
  template <typename T> void input_integer(T &var) noexcept {
    var = 0;
    T sign = 1;
    int cc = getc_x(fp_);
    for (; cc < '0' || '9' < cc; cc = getc_x(fp_))
      if (cc == '-')
        sign = -1;
    for (; '0' <= cc && cc <= '9'; cc = getc_x(fp_))
      var = (var << 3) + (var << 1) + cc - '0';
    var = var * sign;
  }
  inline int c() noexcept { return getc_x(fp_); }
  template <typename T, typename enable_if<is_integral<T>::value,
                                           nullptr_t>::type = nullptr>
  inline MaiScanner &operator>>(T &var) noexcept {
    input_integer<T>(var);
    return *this;
  }
  inline MaiScanner &operator>>(string &var) {
    int cc = getc_x(fp_);
    for (; !isvisiblechar(cc); cc = getc_x(fp_))
      ;
    for (; isvisiblechar(cc); cc = getc_x(fp_))
      var.push_back(cc);
    return *this;
  }
  template <typename IT> inline void in(IT begin, IT end) {
    for (auto it = begin; it != end; ++it)
      *this >> *it;
  }
};
class MaiPrinter {
  FILE *fp_;

public:
  inline MaiPrinter(FILE *fp) : fp_(fp) {}
  template <typename T> void output_integer(T var) noexcept {
    if (var == 0) {
      putc_x('0', fp_);
      return;
    }
    if (var < 0)
      putc_x('-', fp_), var = -var;
    char stack[32];
    int stack_p = 0;
    while (var)
      stack[stack_p++] = '0' + (var % 10), var /= 10;
    while (stack_p)
      putc_x(stack[--stack_p], fp_);
  }
  inline MaiPrinter &operator<<(char c) noexcept {
    putc_x(c, fp_);
    return *this;
  }
  template <typename T, typename enable_if<is_integral<T>::value,
                                           nullptr_t>::type = nullptr>
  inline MaiPrinter &operator<<(T var) noexcept {
    output_integer<T>(var);
    return *this;
  }
  inline MaiPrinter &operator<<(char *str_p) noexcept {
    while (*str_p)
      putc_x(*(str_p++), fp_);
    return *this;
  }
  inline MaiPrinter &operator<<(const string &str) {
    const char *p = str.c_str();
    const char *l = p + str.size();
    while (p < l)
      putc_x(*p++, fp_);
    return *this;
  }
  template <typename IT> void join(IT begin, IT end, char sep = ' ') {
    for (bool b = 0; begin != end; ++begin, b = 1)
      b ? *this << sep << *begin : *this << *begin;
  }
};
MaiScanner scanner(stdin);
MaiPrinter printer(stdout);

struct P {
  using T = int;
  T y, x;

  inline explicit P(T _y, T _x) : y(_y), x(_x) {}
  inline P() : y(0), x(0) {}

  inline bool operator==(P p) const { return y == p.y && x == p.x; }
  inline bool operator<(P p) const { return y == p.y ? x < p.x : y < p.y; }
  inline P operator+(P p) const { return P(y + p.y, x + p.x); }
  inline P operator-(P p) const { return P(y - p.y, x - p.x); }
  inline P &operator+=(P p) {
    y += p.y;
    x += p.x;
    return *this;
  }
  inline P &operator-=(P p) {
    y -= p.y;
    x -= p.x;
    return *this;
  }
  inline P &operator-=(T m) {
    y *= m;
    x;
    return *this;
  }
  inline T distM(P p) const { return abs(y - p.y) + abs(x - p.x); }
  inline T distC(P p) const { return max(abs(y - p.y), abs(x - p.x)); }
  template <typename ITR> ITR nearestM(ITR begin, ITR end) const {
    if (begin == end)
      return end;
    T best = distM(*begin);
    ITR besti = begin;
    for (ITR it = begin; ++it, it != end;) {
      T m = distM(*it);
      if (best < m) {
        best = m;
        besti = it;
      }
    }
    return besti;
  }
};
inline ostream &operator<<(ostream &os, P p) {
  os << '(' << p.y << ',' << p.x << ')';
  return os;
}

const P FourMoving[] = {P(-1, 0), P(0, 1), P(1, 0), P(0, -1)};
const P FiveMoving[] = {P(-1, 0), P(0, 1), P(1, 0), P(0, -1), P(0, 0)};
const P EightMoving[] = {P(-1, 0),  P(0, 1),  P(1, 0),  P(0, -1),
                         P(-1, -1), P(-1, 1), P(1, -1), P(1, 1)};

inline P operator*(P::T m, P p) noexcept { return P(m * p.y, m * p.x); }

template <typename T>
// using T = int;
struct F {
  int height, width;
  vector<T> data;

  F(int h = 1, int w = 1) : height(h), width(w), data(h * w) {}

  inline T &operator()(int y, int x) { return data[x + y * width]; }
  inline T &operator()(P p) { return data[p.x + p.y * width]; }
  inline T operator()(int y, int x) const { return data[x + y * width]; }
  inline T operator()(P p) const { return data[p.x + p.y * width]; }

  inline bool safe(int y, int x) const {
    return 0 <= y && y < height && 0 <= x && x < width;
  }
  inline bool safe(P p) const {
    return 0 <= p.y && p.y < height && 0 <= p.x && p.x < width;
  }

  inline void fill(T e) { std::fill(all(data), e); }
  inline void resize(int h, int w) {
    height = h;

    width = w;
    data.resize(h * w);
  }

  void print(ostream &os, int setw_arg = 4) {
    for (int y = 0; y < height; ++y) {
      for (int x = 0; x < width; ++x)
        os << setw(setw_arg) << operator()(y, x) << ' ';
      os << '\n';
    }
  }
};
// Edge構造体を定義する無向グラフ
class GraphE {
public:
  using W_T = int;
  struct Edge {
    int u, v;
    W_T value;
    Edge(int from = 0, int to = 0, W_T value = 0)
        : u(from), v(to), value(value) {}
    inline int to(int _v) const { return _v == v ? u : v; }
  };
  size_t n;
  vector<vector<int>> vertex_to;
  vector<Edge> edges;

  explicit GraphE(int n = 1) : n(n), vertex_to(n) {}

  inline size_t size() const noexcept { return n; }
  void resize(size_t _n) { vertex_to.resize(n = _n); }
  void connect(int from, int to, W_T val = 0) {
    vertex_to[(size_t)from].push_back((int)edges.size());
    vertex_to[(size_t)to].push_back((int)edges.size());
    edges.emplace_back(from, to, val);
  }
  void connect(vector<Edge> &&es) {
    edges = move(es);
    for (int i = 0; (size_t)i < edges.size(); ++i) {
      vertex_to[edges[i].u].push_back(i);
      vertex_to[edges[i].v].push_back(i);
    }
  }
};

//

int H, W, K;
int startx, starty, goalx, goaly;

//

F<int> field;
F<int> dist;
// GraphE graph;

inline int cv(int y, int x) { return y * W + x; }

int main() {
  scanner >> H >> W >> K;
  scanner >> starty >> startx >> goaly >> goalx;
  --startx;
  --starty;
  --goalx;
  --goaly;

  field.resize(H, W);
  // graph.resize(H*W);

  repeat(i, H) {
    string str;
    scanner >> str;
    repeat(j, W) {
      char c = str[j];
      field(i, j) = c == '@';
    }
  }

  dist.resize(H, W);
  dist.fill(1e9);

  queue<P> que;
  que.emplace(starty, startx);
  dist(starty, startx) = 0;
  while (!que.empty()) {
    auto p = que.front();
    que.pop();
    auto d = dist(p);
    if (p == P(goaly, goalx)) {
      cout << d << endl;
      exit(0); // memfree by os
    }
    for (auto v : FourMoving) {
      auto p2 = v + p;
      repeat(i, K) {
        if (!field.safe(p2))
          break;
        if (field(p2))
          break;
        if (dist(p2) < d + 1)
          break;

        if (dist(p2) > d + 1) {
          dist(p2) = d + 1;
          que.push(p2);
        }
        p2 += v;
      }
    }
    // repeat(i, H) {
    //   repeat(j, W) {
    //     cout << min(dist(i,j), 9);
    //   }
    //   cout << endl;
    // }
    // cout << endl;
  }

  cout << "-1" << endl;
  exit(0);

  return 0;
}