Problem p03725 (C++)

Buggy submission (status: Time Limit Exceeded):
#ifndef DEBUG
#define NDEBUG
#endif
#include <algorithm>
#include <array>
#include <cassert>
#include <iostream>
#include <iterator>
#include <limits>
#include <numeric>
#include <queue>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

using namespace std;

// template {{{
// misc {{{
using Z = long long;
[[maybe_unused]] constexpr Z INF = numeric_limits<Z>::max() / 3;
// }}}

// debug {{{
template <class T>
using enable_if_sequence_t = enable_if_t<
    is_same<typename iterator_traits<typename remove_cv_t<
                remove_reference_t<T>>::iterator>::iterator_category,
            random_access_iterator_tag>{}>;
#ifdef NDEBUG
#define dump(x)
#define debug if (0)
template <class T> inline T &&ix(T &&value) { return value; }
template <class T, class Index, class... Indices,
          class = enable_if_sequence_t<T>>
inline auto &&ix(T &&container, Index index, Indices... indices) {
  return ix(container[index], indices...);
}
#else
#define dump(x)                                                                \
  do {                                                                         \
    cerr << "\e[33m[dump: " << __LINE__ << "] " << (#x) << " = " << x          \
         << "\e[0m" << endl;                                                   \
  } while (0);
#define debug
template <class T>
inline auto &&ix_impl([[maybe_unused]] int line,
                      [[maybe_unused]] const char *code, T &&value) {
  return value;
}
template <class T, class Index, class... Indices,
          class = enable_if_sequence_t<T>>
inline auto &&ix_impl(int line, const char *code, T &&container, Index index,
                      Indices... indices) {
  if (index < 0) {
    cerr << "\e[31mix: negative index at line " << line << ", ix(" << code
         << ")\e[0m" << endl;
    exit(1);
  }
  int size = container.size();
  if (index >= size) {
    cerr << "\e[31mix: index out of range at line " << line << ", ix(" << code
         << ")\n"
         << "index = " << index << " whereas size = " << size << "\e[0m"
         << endl;
    exit(1);
  }
  return ix_impl(line, code, container[index], indices...);
}
#define ix(...) ix_impl(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
// }}}

// IO {{{
template <class T, class U> ostream &operator<<(ostream &os, pair<T, U> p) {
  os << '(' << p.first << ", " << p.second << ')';
  return os;
}
template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}
template <class T> false_type is_container_impl(...);
template <class T, class = typename T::iterator> true_type is_container_impl(T);
template <class T>
struct is_container : decltype(is_container_impl<T>(declval<T>())) {};
template <> struct is_container<string> : std::false_type {};
template <class Container, class = enable_if_t<is_container<Container>{}>>
istream &operator>>(istream &is, Container &cont) {
  for (auto &v : cont)
    is >> v;
  return is;
}
template <class Container, class = enable_if_t<is_container<Container>{}>>
ostream &operator<<(ostream &os, Container const &cont) {
  bool first = true;
  constexpr char sep =
      is_container<typename Container::value_type>{} ? '\n' : ' ';
  for (auto const &v : cont) {
    if (!first) {
      os << sep;
    }
    first = false;
    os << v;
  }
  return os;
}
// }}}
// }}}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.precision(10);
  cout << fixed;
  Z H, W, K;
  cin >> H >> W >> K;
  vector<string> A(H + 2);
  ix(A, 0) = ix(A, H + 1) = string(W + 2, '#');
  Z sx, sy;
  for (auto i = 0; i < H; i++) {
    string s;
    cin >> s;
    ix(A, i + 1) = '#' + s + '#';
    Z spos = s.find('S');
    if (spos < s.size()) {
      sx = i + 1;
      sy = spos + 1;
    }
  }
  dump(A);
  dump(sx);
  dump(sy);
  Z min_dist = min({sx - 1, sy - 1, H - sx, W - sy});
  queue<pair<Z, Z>> que;
  que.emplace(sx, sy);
  vector<vector<Z>> dists(H + 2, vector<Z>(W + 2, INF));
  ix(dists, sx, sy) = 0;
  while (!que.empty()) {
    Z x, y;
    tie(x, y) = que.front();
    dump(x);
    dump(y);
    que.pop();
    array<Z, 4> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
    for (auto i = 0; i < 4; i++) {
      Z nx = x + ix(dx, i), ny = y + ix(dy, i), nd = ix(dists, x, y) + 1;
      dump(nx);
      dump(ny);
      if (ix(A, nx, ny) == '#' || nd > K)
        continue;
      min_dist = min({min_dist, nx - 1, ny - 1, H - nx, W - ny});
      ix(dists, nx, ny) = nd;
      que.emplace(nx, ny);
    }
  }
  cout << 1 + (min_dist / K + (min_dist % K == 0 ? 0 : 1)) << endl;
}


Fixed submission:
#ifndef DEBUG
#define NDEBUG
#endif
#include <algorithm>
#include <array>
#include <cassert>
#include <iostream>
#include <iterator>
#include <limits>
#include <numeric>
#include <queue>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

using namespace std;

// template {{{
// misc {{{
using Z = long long;
[[maybe_unused]] constexpr Z INF = numeric_limits<Z>::max() / 3;
// }}}

// debug {{{
template <class T>
using enable_if_sequence_t = enable_if_t<
    is_same<typename iterator_traits<typename remove_cv_t<
                remove_reference_t<T>>::iterator>::iterator_category,
            random_access_iterator_tag>{}>;
#ifdef NDEBUG
#define dump(x)
#define debug if (0)
template <class T> inline T &&ix(T &&value) { return value; }
template <class T, class Index, class... Indices,
          class = enable_if_sequence_t<T>>
inline auto &&ix(T &&container, Index index, Indices... indices) {
  return ix(container[index], indices...);
}
#else
#define dump(x)                                                                \
  do {                                                                         \
    cerr << "\e[33m[dump: " << __LINE__ << "] " << (#x) << " = " << x          \
         << "\e[0m" << endl;                                                   \
  } while (0);
#define debug
template <class T>
inline auto &&ix_impl([[maybe_unused]] int line,
                      [[maybe_unused]] const char *code, T &&value) {
  return value;
}
template <class T, class Index, class... Indices,
          class = enable_if_sequence_t<T>>
inline auto &&ix_impl(int line, const char *code, T &&container, Index index,
                      Indices... indices) {
  if (index < 0) {
    cerr << "\e[31mix: negative index at line " << line << ", ix(" << code
         << ")\e[0m" << endl;
    exit(1);
  }
  int size = container.size();
  if (index >= size) {
    cerr << "\e[31mix: index out of range at line " << line << ", ix(" << code
         << ")\n"
         << "index = " << index << " whereas size = " << size << "\e[0m"
         << endl;
    exit(1);
  }
  return ix_impl(line, code, container[index], indices...);
}
#define ix(...) ix_impl(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
// }}}

// IO {{{
template <class T, class U> ostream &operator<<(ostream &os, pair<T, U> p) {
  os << '(' << p.first << ", " << p.second << ')';
  return os;
}
template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}
template <class T> false_type is_container_impl(...);
template <class T, class = typename T::iterator> true_type is_container_impl(T);
template <class T>
struct is_container : decltype(is_container_impl<T>(declval<T>())) {};
template <> struct is_container<string> : std::false_type {};
template <class Container, class = enable_if_t<is_container<Container>{}>>
istream &operator>>(istream &is, Container &cont) {
  for (auto &v : cont)
    is >> v;
  return is;
}
template <class Container, class = enable_if_t<is_container<Container>{}>>
ostream &operator<<(ostream &os, Container const &cont) {
  bool first = true;
  constexpr char sep =
      is_container<typename Container::value_type>{} ? '\n' : ' ';
  for (auto const &v : cont) {
    if (!first) {
      os << sep;
    }
    first = false;
    os << v;
  }
  return os;
}
// }}}
// }}}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.precision(10);
  cout << fixed;
  Z H, W, K;
  cin >> H >> W >> K;
  vector<string> A(H + 2);
  ix(A, 0) = ix(A, H + 1) = string(W + 2, '#');
  Z sx, sy;
  for (auto i = 0; i < H; i++) {
    string s;
    cin >> s;
    ix(A, i + 1) = '#' + s + '#';
    Z spos = s.find('S');
    if (spos < s.size()) {
      sx = i + 1;
      sy = spos + 1;
    }
  }
  dump(A);
  dump(sx);
  dump(sy);
  Z min_dist = min({sx - 1, sy - 1, H - sx, W - sy});
  queue<pair<Z, Z>> que;
  que.emplace(sx, sy);
  vector<vector<Z>> dists(H + 2, vector<Z>(W + 2, INF));
  ix(dists, sx, sy) = 0;
  while (!que.empty()) {
    Z x, y;
    tie(x, y) = que.front();
    dump(x);
    dump(y);
    que.pop();
    array<Z, 4> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
    for (auto i = 0; i < 4; i++) {
      Z nx = x + ix(dx, i), ny = y + ix(dy, i), nd = ix(dists, x, y) + 1;
      dump(nx);
      dump(ny);
      if (ix(A, nx, ny) == '#' || ix(dists, nx, ny) < INF || nd > K)
        continue;
      min_dist = min({min_dist, nx - 1, ny - 1, H - nx, W - ny});
      ix(dists, nx, ny) = nd;
      que.emplace(nx, ny);
    }
  }
  cout << 1 + (min_dist / K + (min_dist % K == 0 ? 0 : 1)) << endl;
}