Problem p02579 (C++)

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

#define el '\n'
#define pb push_back
#define sp ' '
#define all(x) (x).begin(), (x).end()
#define mset(x, y) memset(x, y, sizeof(x))
#define ff first
#define ss second

// clang-format off
bool chmin(int& a, int b){ return b < a ? a = b, true : false; }
bool chmax(int& a, int b){ return b > a ? a = b, true : false; }
bool chmin(long long& a, long long b){ return b < a ? a = b, true : false; }
bool chmax(long long& a, long long b){ return b > a ? a = b, true : false; }
#ifndef ONLINE_JUDGE
template <typename T, size_t N> int SIZE(const T (&t)[N]){ return N; } template<typename T> int SIZE(const T &t){ return t.size(); } string to_string(const string s, int x1=0, int x2=1e9){ return '"' + ((x1 < (int)s.size()) ? s.substr(x1, x2-x1+1) : "") + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(const bool b) { return (b ? "true" : "false"); } string to_string(const char c){ return string({c}); } template<size_t N> string to_string(const bitset<N> &b, int x1=0, int x2=1e9){ string t = ""; for(int __iii__ = min(x1,SIZE(b)),  __jjj__ = min(x2, SIZE(b)-1); __iii__ <= __jjj__; ++__iii__){ t += b[__iii__] + '0'; } return '"' + t + '"'; } template <typename A, typename... C> string to_string(const A (&v), int x1=0, int x2=1e9, C... coords); int l_v_l_v_l = 0, t_a_b_s = 0; template <typename A, typename B> string to_string(const pair<A, B> &p) { l_v_l_v_l++; string res = "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; l_v_l_v_l--; return res; } template <typename A, typename... C> string to_string(const A (&v), int x1, int x2, C... coords) { int rnk = rank<A>::value; string tab(t_a_b_s, ' '); string res = ""; bool first = true; if(l_v_l_v_l == 0) res += el; res += tab + "["; x1 = min(x1, SIZE(v)), x2 = min(x2, SIZE(v)); auto l = begin(v); advance(l, x1); auto r = l; advance(r, (x2-x1) + (x2 < SIZE(v))); for (auto e = l; e != r; e = next(e)) { if (!first) { res += ", "; } first = false; l_v_l_v_l++; if(e != l){ if(rnk > 1) { res += el; t_a_b_s = l_v_l_v_l; }; } else{ t_a_b_s = 0; } res += to_string(*e, coords...); l_v_l_v_l--; } res += "]"; if(l_v_l_v_l == 0) res += el; return res; } void dbgm(){;} template<typename Heads, typename... Tails> void dbgm(Heads H, Tails... T){ cout << to_string(H) << " | "; dbgm(T...); } 
#define dbg(...) cout << "[" << #__VA_ARGS__ << "]: "; cout << to_string(__VA_ARGS__) << endl
#define dbgm(...) cout << "[" << #__VA_ARGS__ << "]: "; dbgm(__VA_ARGS__); cout << endl
#else
#define dbg(...) ;
#define dbgm(...) ;
#endif
// clang-format on

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, pii> ppi;
typedef pair<ll, ll> pll;
typedef pair<int, ll> pil;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<pll> vpll;
typedef vector<vpii> vvpii;
typedef vector<vpll> vvpll;

const int inf = 1e09 + 5e3;
const ll linf = 2e18 + 5e3;
const int mod = 1e9 + 7;
const int mxn = 1e6 + 30;

int h, w, ch, cw, dh, dw;
vvi maz;

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

bool check(int a, int b) {
  return a >= 0 && a < h && b >= 0 && b < w && maz[a][b] == 0;
}

ll bfs(pii s, pii e) {
  set<vll> q; // val, x,y,
  vvll used(1e3 + 5, vll(1e3 + 5, linf));

  q.insert({0, s.ff, s.ss});
  used[s.ff][s.ss] = 0;
  while (!q.empty()) {
    auto v = *q.begin();
    q.erase(q.begin());
    // dbg(v);
    if (v[1] == e.ff && v[2] == e.ss)
      return v[0];
    if (used[v[1]][v[2]] < v[0])
      continue;
    for (int z = 0; z < 4; z++) {
      int l = dx[z];
      int k = dy[z];
      int nx = v[1] + k;
      int ny = v[2] + l;
      if (!check(nx, ny) || used[nx][ny] <= v[0])
        continue;
      used[nx][ny] = v[0];
      q.insert({v[0], nx, ny});
    }
    for (int k : {-2, -1, 0, 1, 2}) {
      for (int l : {-2, -1, 0, 1, 2})
        if ((l != 0 || k != 0)) {
          int nx = v[1] + k;
          int ny = v[2] + l;
          if (!check(nx, ny) || used[nx][ny] <= v[0] + 1)
            continue;
          used[nx][ny] = v[0] + 1;
          q.insert({v[0] + 1, nx, ny});
        }
    }
  }
  return -1;
}

int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

  cin >> h >> w >> ch >> cw >> dh >> dw;
  ch--, cw--, dh--, dw--;
  maz.assign(1e3 + 3, vi(1e3 + 3));
  string stemp;
  for (int i = 0; i < h; i++) {
    cin >> stemp;
    assert(stemp.size() == h);
    for (int j = 0; j < h; j++) {
      maz[i][j] = stemp[j] == '#';
    }
  }
  // dbg(maz);
  cout << bfs({ch, cw}, {dh, dw});
}


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

#define el '\n'
#define pb push_back
#define sp ' '
#define all(x) (x).begin(), (x).end()
#define mset(x, y) memset(x, y, sizeof(x))
#define ff first
#define ss second

// clang-format off
bool chmin(int& a, int b){ return b < a ? a = b, true : false; }
bool chmax(int& a, int b){ return b > a ? a = b, true : false; }
bool chmin(long long& a, long long b){ return b < a ? a = b, true : false; }
bool chmax(long long& a, long long b){ return b > a ? a = b, true : false; }
#ifndef ONLINE_JUDGE
template <typename T, size_t N> int SIZE(const T (&t)[N]){ return N; } template<typename T> int SIZE(const T &t){ return t.size(); } string to_string(const string s, int x1=0, int x2=1e9){ return '"' + ((x1 < (int)s.size()) ? s.substr(x1, x2-x1+1) : "") + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(const bool b) { return (b ? "true" : "false"); } string to_string(const char c){ return string({c}); } template<size_t N> string to_string(const bitset<N> &b, int x1=0, int x2=1e9){ string t = ""; for(int __iii__ = min(x1,SIZE(b)),  __jjj__ = min(x2, SIZE(b)-1); __iii__ <= __jjj__; ++__iii__){ t += b[__iii__] + '0'; } return '"' + t + '"'; } template <typename A, typename... C> string to_string(const A (&v), int x1=0, int x2=1e9, C... coords); int l_v_l_v_l = 0, t_a_b_s = 0; template <typename A, typename B> string to_string(const pair<A, B> &p) { l_v_l_v_l++; string res = "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; l_v_l_v_l--; return res; } template <typename A, typename... C> string to_string(const A (&v), int x1, int x2, C... coords) { int rnk = rank<A>::value; string tab(t_a_b_s, ' '); string res = ""; bool first = true; if(l_v_l_v_l == 0) res += el; res += tab + "["; x1 = min(x1, SIZE(v)), x2 = min(x2, SIZE(v)); auto l = begin(v); advance(l, x1); auto r = l; advance(r, (x2-x1) + (x2 < SIZE(v))); for (auto e = l; e != r; e = next(e)) { if (!first) { res += ", "; } first = false; l_v_l_v_l++; if(e != l){ if(rnk > 1) { res += el; t_a_b_s = l_v_l_v_l; }; } else{ t_a_b_s = 0; } res += to_string(*e, coords...); l_v_l_v_l--; } res += "]"; if(l_v_l_v_l == 0) res += el; return res; } void dbgm(){;} template<typename Heads, typename... Tails> void dbgm(Heads H, Tails... T){ cout << to_string(H) << " | "; dbgm(T...); } 
#define dbg(...) cout << "[" << #__VA_ARGS__ << "]: "; cout << to_string(__VA_ARGS__) << endl
#define dbgm(...) cout << "[" << #__VA_ARGS__ << "]: "; dbgm(__VA_ARGS__); cout << endl
#else
#define dbg(...) ;
#define dbgm(...) ;
#endif
// clang-format on

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, pii> ppi;
typedef pair<ll, ll> pll;
typedef pair<int, ll> pil;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<pll> vpll;
typedef vector<vpii> vvpii;
typedef vector<vpll> vvpll;

const int inf = 1e09 + 5e3;
const ll linf = 2e18 + 5e3;
const int mod = 1e9 + 7;
const int mxn = 1e6 + 30;

int h, w, ch, cw, dh, dw;
vvi maz;

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

bool check(int a, int b) {
  return a >= 0 && a < h && b >= 0 && b < w && maz[a][b] == 0;
}

ll bfs(pii s, pii e) {
  set<vll> q; // val, x,y,
  vvll used(1e3 + 5, vll(1e3 + 5, linf));

  q.insert({0, s.ff, s.ss});
  used[s.ff][s.ss] = 0;
  while (!q.empty()) {
    auto v = *q.begin();
    q.erase(q.begin());
    // dbg(v);
    if (v[1] == e.ff && v[2] == e.ss)
      return v[0];
    if (used[v[1]][v[2]] < v[0])
      continue;
    for (int z = 0; z < 4; z++) {
      int l = dx[z];
      int k = dy[z];
      int nx = v[1] + k;
      int ny = v[2] + l;
      if (!check(nx, ny) || used[nx][ny] <= v[0])
        continue;
      used[nx][ny] = v[0];
      q.insert({v[0], nx, ny});
    }
    for (int k : {-2, -1, 0, 1, 2}) {
      for (int l : {-2, -1, 0, 1, 2})
        if ((l != 0 || k != 0)) {
          int nx = v[1] + k;
          int ny = v[2] + l;
          if (!check(nx, ny) || used[nx][ny] <= v[0] + 1)
            continue;
          used[nx][ny] = v[0] + 1;
          q.insert({v[0] + 1, nx, ny});
        }
    }
  }
  return -1;
}

int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

  cin >> h >> w >> ch >> cw >> dh >> dw;
  ch--, cw--, dh--, dw--;
  maz.assign(1e3 + 3, vi(1e3 + 3));
  string stemp;
  for (int i = 0; i < h; i++) {
    cin >> stemp;
    assert(stemp.size() == w);
    for (int j = 0; j < w; j++) {
      maz[i][j] = stemp[j] == '#';
    }
  }
  // dbg(maz);
  cout << bfs({ch, cw}, {dh, dw});
}