Problem p02579 (C++)

Buggy submission (status: Time Limit Exceeded):
/* Aa^~ kokoro ga pyonpyon suru n jaa^~
// ZZZXXkXkkkZ!``` ``` ``` ``` ``` ``` ``` ``` ``` ``` ```
```?Wfpppbpbbpbbpbbbkbkk
// ppbbbpbbpVr`` `` ` ` ` ` ```` `` ` ` ``  ` ` ` ` ` ` ` ` `
dppbbkkkkkkkkkkqkqkk
// HkqqqqqkkWr`` ` ` ``` ``` `?G, ` ` ``.JC!```` ` ` `` ``
````(Wpbkkkkkkkkqkkkkkqk
// mmmmmqqqqpr` `` `` ```````.+zT=`` `` 7TO-.```````` `` ``
```(yppbkkkkkkkkkkkkkkk
// ggmgmmqqqH$ ``````````....````` `  ````````.`````` ``
``````.yfpppbbbbkkkkqqqqqH
// gmmmmmqqqkW<```` `````...`````  .,.`  ````....````` ```````
(Wbqqmgmmgmggggggggg
// qmmmqqqqkkWk.``````````````````` ;:<``
`````.`````````````-_<-?WHHqmmmmmmgmmgggg
// @@@@@@@gggHH6- ``````````````` `` _ `` ````````````````
._~~_.`-?Wkqmmmmmmmggg@g
// @@@@g@gggHY~.-<_- ``````````````````````````````````
._~~(<-``.`.(WHqqqmmggggmmm
// @@g@gggHH=.`..._<-___..```````````````````````. .-_~~~_(!``-.``.``
OHHWUWHmqHWXW
// gggggmqK1.``..~.. _<<+-(____..  ````````  ..__~~_((<<!.`.``` .``.``
j0C1XUHmHIdW
// ggmmqH0!,_``.>`````` _<<;<v<<<++((((((((((<<<<<<~_. (-.``~``.>..```
jOuWHHqHIdH
// gmmqkW!`(_ J>`    `` ` _~<`_~~~~<<<<<<<~~__````````` ?1. ._`(__``` zXWHg@HkXH
// gHHWS{``(lJ<!``.``.```(:+>`._`````.` <..`` - ``. `   _ ?&._.I`_``````
.XyVfppppW
// HHHSv``.(X:_..... _..(;+<!.(<..-.....-.-_..+_`..<.`.`..`_IJd}
.`..````jqg@@@@@@
// XHWZ{..<Jk~!.`..
(<.-(+>(_.(1.(_..`.`.`.<_.+<_..<<-..._..-zy>.`_`...```.WH@HHHHH
// bkWt~.-jCz(_..`.(+<.(;<
._-<=_(<_..-....(_.<1<..(<<.`._..-JUS-._.`...```dHmH9VUH
// WUUO..(f.(c...__+z<-(+~`
_-+<_(><..__.`.(<._.z_.(1;_..__.(C(zT-(..`...``(WHR<+Xk
//
kkkk._(_.->..._(z;:_><.._>_+_<(1>_._<...(v<<.(<.(+z<..-_(Z~_<_j+_..`...`(WHKz1ZW
//
@@gR._+_..~..-<+z<<?<>```_.<_.(+1><_;_..(1_:`.<<??1z--(+Z!..<_.j<....`..(bgHAAQX
// @@mR.(j:..~.._<z!`.(>~```
~(_.(+<1><><_.(((_`.<__`.<_.(X>...<_.(<.....`.JUWWWyWW
//
@gmH_(zl..(.._+>```<+_````.~>``(+.<?>>_._(<```(<<``(__<>....<.._<.......dXkkkHHH
//
mmqHl(dk_.(_.-=~`.`.1-..._~-1.``_:`(??<_~(`.--.&_.`.<(;<...._.._<..`..._Xg@@@@@@
//
qHkpk(dX<.(;..j_```.(((JJ&a&-~``````.1<_```-(((e+.-(/`(>...._..(<......(Wmggg@@g
// HVHbWcz><__+_.(_.(dWWHHH@HHc~````````.+~``
(jHMMMHHHm&.?..._<..(<_..._.(WqqHHmHg
// 0>vWWkzZwl~<o.__`__~X@@HM@Hb ```.`.``. ````
d@@HHH@@K?76...(<..(<_...(_(ppWWWWHq
// X0XWHKXXw$<(z<.( ``
WHHMHHHH_``````````````.WHHMNMHHH_`(...(<_.(z_..._<(fWVC174W
//
XuXWHHWWz>__+z+.!`..??CZYCOX_`````````````.`~.OvTUZUS_`~.._+?_.(_~_.._zjO=1+~+jy
// kkkkkkkkX:._<z=1(_`` << ``->``.``.``.``.```` ?<``
(v!`._..(??_.(1._.._=dUOOzzzwX
// @@@@@@@@H<...1O=v<_...__ -_````````````````.`` `` ~.``
:.~+=?~.(;_(...jdQQQQQkkk
//
H@@@@@@@H~...(==>.~~~~~....`.`````````.`````.`........->.(===~~<<.(...(dg@@@@@@@
//
@@@H@@HHH_.__(=l>~.~~~~~....``.``.``.```..`......~~~~~(<_+=l=~_<.->..~_dqggggg@g
//
@H@@@@MHH_._<(=l>...........```````````````.`...~~~~~~+<(=lz=~((j=z_..~jWqmmgggm
//
@@H@@HHWH_._<(lll-.......```.````.``.`..`````........_z<+llZz~(lOO=<...(VYUUUW9Y
//
@@HMMHWZf>~_=:=llw+.`````````.`.```__~~_``.`````.....(z+llOOz_zllOlz~..~<<1+dW>_
//
MMM#MHHWXl~_=>1ltwOl&.`.``.`````.``````````````.````.(llttwtz(OltwOz<..__zwOwwOz
//
HM#HMHUUI<._1z+ttOZttlt&....``.``.`.````.``...``...(zZtttOktzjttttwlz_._<(Xkkkkk
//
HHHmHSZu:(_~+OztttXtttOZZttO+-..............-(+ztOttwttttd0tOZttttwOl<~.(_dMMHHH
//
rvuuXuuI~~<~(uttttwvOwwwkQQHMMHHHHHHHHHMMMNmgey?OwwwrtttwXOtwttttttXtO-~.((wZyyy
// HHHHHHK>(~(-(dOrtrrl(QgMHMMMHHHHHHHHHHHHHHHH##HMNkX0rrrrXXrd%``
(Ctwwtz_~.<(Wg@H
// NNNNNHD(~(zo~zXrrrQdHHMMNMHHHHHHHHHHHHHHHHHHHHHH##HNmyrdKkwZ `
_``-zwrt1~~_<(MNM
// MMMMM#<<_jwr:(Z4QHHMMHMHHHHHHHHHHHHHHHHHHHHHHHHHHHH###NHSXZ>`
~````.OXtt>~._<?MM
*/

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

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a) begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

#define FF first
#define SS second

template <class S, class T> istream &operator>>(istream &is, pair<S, T> &p) {
  return is >> p.FF >> p.SS;
}
template <class T> istream &operator>>(istream &is, vector<T> &xs) {
  for (auto &x : xs)
    is >> x;
  return is;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
  return os << p.FF << " " << p.SS;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &xs) {
  for (unsigned int i = 0; i < xs.size(); ++i)
    os << (i ? " " : "") << xs[i];
  return os;
}
template <class T> void maxi(T &x, T y) {
  if (x < y)
    x = y;
}
template <class T> void mini(T &x, T y) {
  if (x > y)
    x = y;
}
void debug(istringstream &) {}
template <char sep = ',', class Head, class... Tail>
void debug(istringstream &iss, Head &&head, Tail &&...tail) {
  string name;
  getline(iss, name, ',');
  cout << sep << name << "=" << head;
  debug(iss, forward<Tail>(tail)...);
}

#ifdef PYONPOI
#define DEBUG(...)                                                             \
  do {                                                                         \
    istringstream ss(#__VA_ARGS__);                                            \
    debug<' '>(ss, __VA_ARGS__);                                               \
    cout << endl;                                                              \
  } while (0)
#else
#define DEBUG
#endif
void init_io(int argc, char *argv[]) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
#ifdef PYONPOI
  if (argc > 1) {
    ifstream *ifs = new ifstream();
    ifs->open(argv[1]);
    cin.rdbuf(ifs->rdbuf());
  }
#endif
}

const double EPS = 1e-10;
const double PI = acos(-1.0);
const LL MOD = 1e9 + 7;

int dx[] = {-1, 0, 1, 0};
int dy[] = {0, -1, 0, 1};

int main(int argc, char *argv[]) {
  init_io(argc, argv);

  int H, W;
  cin >> H >> W;

  PII S, T;
  cin >> S >> T;
  S.FF--;
  S.SS--;
  T.FF--;
  T.SS--;

  VVI obs(H, VI(W));
  REP(y, H) REP(x, W) {
    char c;
    cin >> c;
    obs[y][x] = (c == '#');
  }

  const int INF = 1e9;
  VVI dist(H, VI(W, INF));
  deque<PII> dq;
  dq.push_back(S);
  dist[S.FF][S.SS] = 0;

  auto isin = [&](PII p) {
    return 0 <= p.FF && p.FF < H && 0 <= p.SS && p.SS < W;
  };

  while (!dq.empty()) {
    auto p = dq.front();
    dq.pop_front();

    int cur = dist[p.FF][p.SS];

    REP(d, 4) {
      PII np = p;
      np.FF += dy[d];
      np.SS += dx[d];

      if (!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur)
        continue;
      dist[np.FF][np.SS] = cur;
      dq.push_front(np);
    }

    FOR(ty, -2, 2 + 1) FOR(tx, -2, 2 + 1) {
      PII np = p;
      np.FF += ty;
      np.SS += tx;

      if (!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur + 1)
        continue;
      dist[np.FF][np.SS] = cur + 1;
      dq.push_front(np);
    }
  }

  int ans = dist[T.FF][T.SS];
  if (ans == INF)
    ans = -1;
  cout << ans << endl;

  return 0;
}


Fixed submission:
/* Aa^~ kokoro ga pyonpyon suru n jaa^~
// ZZZXXkXkkkZ!``` ``` ``` ``` ``` ``` ``` ``` ``` ``` ```
```?Wfpppbpbbpbbpbbbkbkk
// ppbbbpbbpVr`` `` ` ` ` ` ```` `` ` ` ``  ` ` ` ` ` ` ` ` `
dppbbkkkkkkkkkkqkqkk
// HkqqqqqkkWr`` ` ` ``` ``` `?G, ` ` ``.JC!```` ` ` `` ``
````(Wpbkkkkkkkkqkkkkkqk
// mmmmmqqqqpr` `` `` ```````.+zT=`` `` 7TO-.```````` `` ``
```(yppbkkkkkkkkkkkkkkk
// ggmgmmqqqH$ ``````````....````` `  ````````.`````` ``
``````.yfpppbbbbkkkkqqqqqH
// gmmmmmqqqkW<```` `````...`````  .,.`  ````....````` ```````
(Wbqqmgmmgmggggggggg
// qmmmqqqqkkWk.``````````````````` ;:<``
`````.`````````````-_<-?WHHqmmmmmmgmmgggg
// @@@@@@@gggHH6- ``````````````` `` _ `` ````````````````
._~~_.`-?Wkqmmmmmmmggg@g
// @@@@g@gggHY~.-<_- ``````````````````````````````````
._~~(<-``.`.(WHqqqmmggggmmm
// @@g@gggHH=.`..._<-___..```````````````````````. .-_~~~_(!``-.``.``
OHHWUWHmqHWXW
// gggggmqK1.``..~.. _<<+-(____..  ````````  ..__~~_((<<!.`.``` .``.``
j0C1XUHmHIdW
// ggmmqH0!,_``.>`````` _<<;<v<<<++((((((((((<<<<<<~_. (-.``~``.>..```
jOuWHHqHIdH
// gmmqkW!`(_ J>`    `` ` _~<`_~~~~<<<<<<<~~__````````` ?1. ._`(__``` zXWHg@HkXH
// gHHWS{``(lJ<!``.``.```(:+>`._`````.` <..`` - ``. `   _ ?&._.I`_``````
.XyVfppppW
// HHHSv``.(X:_..... _..(;+<!.(<..-.....-.-_..+_`..<.`.`..`_IJd}
.`..````jqg@@@@@@
// XHWZ{..<Jk~!.`..
(<.-(+>(_.(1.(_..`.`.`.<_.+<_..<<-..._..-zy>.`_`...```.WH@HHHHH
// bkWt~.-jCz(_..`.(+<.(;<
._-<=_(<_..-....(_.<1<..(<<.`._..-JUS-._.`...```dHmH9VUH
// WUUO..(f.(c...__+z<-(+~`
_-+<_(><..__.`.(<._.z_.(1;_..__.(C(zT-(..`...``(WHR<+Xk
//
kkkk._(_.->..._(z;:_><.._>_+_<(1>_._<...(v<<.(<.(+z<..-_(Z~_<_j+_..`...`(WHKz1ZW
//
@@gR._+_..~..-<+z<<?<>```_.<_.(+1><_;_..(1_:`.<<??1z--(+Z!..<_.j<....`..(bgHAAQX
// @@mR.(j:..~.._<z!`.(>~```
~(_.(+<1><><_.(((_`.<__`.<_.(X>...<_.(<.....`.JUWWWyWW
//
@gmH_(zl..(.._+>```<+_````.~>``(+.<?>>_._(<```(<<``(__<>....<.._<.......dXkkkHHH
//
mmqHl(dk_.(_.-=~`.`.1-..._~-1.``_:`(??<_~(`.--.&_.`.<(;<...._.._<..`..._Xg@@@@@@
//
qHkpk(dX<.(;..j_```.(((JJ&a&-~``````.1<_```-(((e+.-(/`(>...._..(<......(Wmggg@@g
// HVHbWcz><__+_.(_.(dWWHHH@HHc~````````.+~``
(jHMMMHHHm&.?..._<..(<_..._.(WqqHHmHg
// 0>vWWkzZwl~<o.__`__~X@@HM@Hb ```.`.``. ````
d@@HHH@@K?76...(<..(<_...(_(ppWWWWHq
// X0XWHKXXw$<(z<.( ``
WHHMHHHH_``````````````.WHHMNMHHH_`(...(<_.(z_..._<(fWVC174W
//
XuXWHHWWz>__+z+.!`..??CZYCOX_`````````````.`~.OvTUZUS_`~.._+?_.(_~_.._zjO=1+~+jy
// kkkkkkkkX:._<z=1(_`` << ``->``.``.``.``.```` ?<``
(v!`._..(??_.(1._.._=dUOOzzzwX
// @@@@@@@@H<...1O=v<_...__ -_````````````````.`` `` ~.``
:.~+=?~.(;_(...jdQQQQQkkk
//
H@@@@@@@H~...(==>.~~~~~....`.`````````.`````.`........->.(===~~<<.(...(dg@@@@@@@
//
@@@H@@HHH_.__(=l>~.~~~~~....``.``.``.```..`......~~~~~(<_+=l=~_<.->..~_dqggggg@g
//
@H@@@@MHH_._<(=l>...........```````````````.`...~~~~~~+<(=lz=~((j=z_..~jWqmmgggm
//
@@H@@HHWH_._<(lll-.......```.````.``.`..`````........_z<+llZz~(lOO=<...(VYUUUW9Y
//
@@HMMHWZf>~_=:=llw+.`````````.`.```__~~_``.`````.....(z+llOOz_zllOlz~..~<<1+dW>_
//
MMM#MHHWXl~_=>1ltwOl&.`.``.`````.``````````````.````.(llttwtz(OltwOz<..__zwOwwOz
//
HM#HMHUUI<._1z+ttOZttlt&....``.``.`.````.``...``...(zZtttOktzjttttwlz_._<(Xkkkkk
//
HHHmHSZu:(_~+OztttXtttOZZttO+-..............-(+ztOttwttttd0tOZttttwOl<~.(_dMMHHH
//
rvuuXuuI~~<~(uttttwvOwwwkQQHMMHHHHHHHHHMMMNmgey?OwwwrtttwXOtwttttttXtO-~.((wZyyy
// HHHHHHK>(~(-(dOrtrrl(QgMHMMMHHHHHHHHHHHHHHHH##HMNkX0rrrrXXrd%``
(Ctwwtz_~.<(Wg@H
// NNNNNHD(~(zo~zXrrrQdHHMMNMHHHHHHHHHHHHHHHHHHHHHH##HNmyrdKkwZ `
_``-zwrt1~~_<(MNM
// MMMMM#<<_jwr:(Z4QHHMMHMHHHHHHHHHHHHHHHHHHHHHHHHHHHH###NHSXZ>`
~````.OXtt>~._<?MM
*/

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

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a) begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)

#define FF first
#define SS second

template <class S, class T> istream &operator>>(istream &is, pair<S, T> &p) {
  return is >> p.FF >> p.SS;
}
template <class T> istream &operator>>(istream &is, vector<T> &xs) {
  for (auto &x : xs)
    is >> x;
  return is;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
  return os << p.FF << " " << p.SS;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &xs) {
  for (unsigned int i = 0; i < xs.size(); ++i)
    os << (i ? " " : "") << xs[i];
  return os;
}
template <class T> void maxi(T &x, T y) {
  if (x < y)
    x = y;
}
template <class T> void mini(T &x, T y) {
  if (x > y)
    x = y;
}
void debug(istringstream &) {}
template <char sep = ',', class Head, class... Tail>
void debug(istringstream &iss, Head &&head, Tail &&...tail) {
  string name;
  getline(iss, name, ',');
  cout << sep << name << "=" << head;
  debug(iss, forward<Tail>(tail)...);
}

#ifdef PYONPOI
#define DEBUG(...)                                                             \
  do {                                                                         \
    istringstream ss(#__VA_ARGS__);                                            \
    debug<' '>(ss, __VA_ARGS__);                                               \
    cout << endl;                                                              \
  } while (0)
#else
#define DEBUG
#endif
void init_io(int argc, char *argv[]) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
#ifdef PYONPOI
  if (argc > 1) {
    ifstream *ifs = new ifstream();
    ifs->open(argv[1]);
    cin.rdbuf(ifs->rdbuf());
  }
#endif
}

const double EPS = 1e-10;
const double PI = acos(-1.0);
const LL MOD = 1e9 + 7;

int dx[] = {-1, 0, 1, 0};
int dy[] = {0, -1, 0, 1};

int main(int argc, char *argv[]) {
  init_io(argc, argv);

  int H, W;
  cin >> H >> W;

  PII S, T;
  cin >> S >> T;
  S.FF--;
  S.SS--;
  T.FF--;
  T.SS--;

  VVI obs(H, VI(W));
  REP(y, H) REP(x, W) {
    char c;
    cin >> c;
    obs[y][x] = (c == '#');
  }

  const int INF = 1e9;
  VVI dist(H, VI(W, INF));
  deque<PII> dq;
  dq.push_back(S);
  dist[S.FF][S.SS] = 0;

  auto isin = [&](PII p) {
    return 0 <= p.FF && p.FF < H && 0 <= p.SS && p.SS < W;
  };

  while (!dq.empty()) {
    auto p = dq.front();
    dq.pop_front();

    int cur = dist[p.FF][p.SS];

    REP(d, 4) {
      PII np = p;
      np.FF += dy[d];
      np.SS += dx[d];

      if (!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur)
        continue;
      dist[np.FF][np.SS] = cur;
      dq.push_front(np);
    }

    FOR(ty, -2, 2 + 1) FOR(tx, -2, 2 + 1) {
      PII np = p;
      np.FF += ty;
      np.SS += tx;

      if (!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur + 1)
        continue;
      dist[np.FF][np.SS] = cur + 1;
      dq.push_back(np);
    }
  }

  int ans = dist[T.FF][T.SS];
  if (ans == INF)
    ans = -1;
  cout << ans << endl;

  return 0;
}