Problem p02735 (C++)

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

using namespace std;

#define DUMP(x) std::cerr << (#x) << " = " << (x) << "\n"
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define EREP(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
#define RREP(i, a, b) for (int i = (int)(a)-1; i >= (int)(b); --i)
#define rep(i, n) REP(i, 0, n)
#define erep(i, n) EREP(i, 0, n)
#define rrep(i, n) RREP(i, n, 0)
#define ALL(r) r.begin(), r.end()
#define YES cout << "YES\n"
#define Yes cout << "Yes\n"
#define NO cout << "NO\n"
#define No cout << "No\n"
#define IMP cout << "IMPOSSIBLE\n"
#define Imp cout << "Impossible\n"
#define imp cout << "impossible\n"
#define M1 cout << "-1\n"
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  os << "{";
  rep(i, v.size()) os << v[i] << (i == (int)v.size() - 1 ? "" : ", ");
  os << "}";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &p) {
  return (os << "(" << p.first << ", " << p.second << ")");
}
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &m) {
  bool first = true;
  os << "{";
  for (const auto e : m) {
    if (!first)
      os << ", ";
    os << "{" << e.first << ": " << e.second << "}";
    first = false;
  }
  os << "}";
  return os;
}
template <typename T> T dup(T x, T y) { return (x + y - 1) / y; };
template <typename A, size_t N, typename T>
inline void arrayFill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
struct in {
  const size_t n = 0;
  in() = default;
  in(size_t n) : n(n){};
  template <typename T> operator T() {
    T ret;
    cin >> ret;
    return ret;
  }
  template <typename T> operator vector<T>() {
    assert(n != 0);
    vector<T> ret(n);
    for (T &x : ret) {
      T tmp = in();
      x = tmp;
    }
    return ret;
  }
  template <typename T, typename U> operator pair<T, U>() {
    pair<T, U> ret;
    ret.first = in();
    ret.second = in();
    return ret;
  }
};

using ll = int64_t;
using vint = vector<int32_t>;
using vvint = vector<vint>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vstr = vector<string>;
using pint = pair<int32_t, int32_t>;
using vpint = vector<pint>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using setint = set<int32_t>;
using setstr = set<string>;
using qint = queue<int32_t>;
using qpint = queue<pint>;

constexpr std::int32_t INF = 1001001001;
constexpr std::int64_t LINF = 1001001001001001001;

void Main() {
  int h = in(), w = in();
  vstr s = in(h);
  vvint dp(h + 2, vint(w + 2, INF));
  dp[0][0] = (s[0][0] == '#');

  rep(i, h) rep(j, w) {
    if (s[i][j] == '.') {
      if (i + 1 < h) {
        if (s[i + 1][j] == '.') {
          chmin(dp[i + 1][j], dp[i][j]);
        } else {
          chmin(dp[i + 1][j], dp[i][j] + 1);
        }
      }

      if (j + 1 < w) {
        if (s[i][j + 1] == '.') {
          chmin(dp[i][j + 1], dp[i][j]);
        } else {
          chmin(dp[i][j + 1], dp[i][j] + 1);
        }
      }
    } else {
      if (i + 1 < h) {
        if (s[i + 1][j] == '.') {
          chmin(dp[i + 1][j], dp[i][j]);
        } else {
          chmin(dp[i + 1][j], dp[i][j]);
        }
      }

      if (j + 1 < w) {
        if (s[i + 1][j] == '.') {
          chmin(dp[i][j + 1], dp[i][j]);
        } else {
          chmin(dp[i][j + 1], dp[i][j]);
        }
      }
    }
  }
  cout << dp[h - 1][w - 1] << endl;
}

signed main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(15);
  Main();
  return 0;
}


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

using namespace std;

#define DUMP(x) std::cerr << (#x) << " = " << (x) << "\n"
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define EREP(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
#define RREP(i, a, b) for (int i = (int)(a)-1; i >= (int)(b); --i)
#define rep(i, n) REP(i, 0, n)
#define erep(i, n) EREP(i, 0, n)
#define rrep(i, n) RREP(i, n, 0)
#define ALL(r) r.begin(), r.end()
#define YES cout << "YES\n"
#define Yes cout << "Yes\n"
#define NO cout << "NO\n"
#define No cout << "No\n"
#define IMP cout << "IMPOSSIBLE\n"
#define Imp cout << "Impossible\n"
#define imp cout << "impossible\n"
#define M1 cout << "-1\n"
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  os << "{";
  rep(i, v.size()) os << v[i] << (i == (int)v.size() - 1 ? "" : ", ");
  os << "}";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &p) {
  return (os << "(" << p.first << ", " << p.second << ")");
}
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &m) {
  bool first = true;
  os << "{";
  for (const auto e : m) {
    if (!first)
      os << ", ";
    os << "{" << e.first << ": " << e.second << "}";
    first = false;
  }
  os << "}";
  return os;
}
template <typename T> T dup(T x, T y) { return (x + y - 1) / y; };
template <typename A, size_t N, typename T>
inline void arrayFill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
struct in {
  const size_t n = 0;
  in() = default;
  in(size_t n) : n(n){};
  template <typename T> operator T() {
    T ret;
    cin >> ret;
    return ret;
  }
  template <typename T> operator vector<T>() {
    assert(n != 0);
    vector<T> ret(n);
    for (T &x : ret) {
      T tmp = in();
      x = tmp;
    }
    return ret;
  }
  template <typename T, typename U> operator pair<T, U>() {
    pair<T, U> ret;
    ret.first = in();
    ret.second = in();
    return ret;
  }
};

using ll = int64_t;
using vint = vector<int32_t>;
using vvint = vector<vint>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vstr = vector<string>;
using pint = pair<int32_t, int32_t>;
using vpint = vector<pint>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using setint = set<int32_t>;
using setstr = set<string>;
using qint = queue<int32_t>;
using qpint = queue<pint>;

constexpr std::int32_t INF = 1001001001;
constexpr std::int64_t LINF = 1001001001001001001;

void Main() {
  int h = in(), w = in();
  vstr s = in(h);
  vvint dp(h + 2, vint(w + 2, INF));
  dp[0][0] = (s[0][0] == '#');

  rep(i, h) rep(j, w) {
    if (s[i][j] == '.') {
      if (i + 1 < h) {
        if (s[i + 1][j] == '.') {
          chmin(dp[i + 1][j], dp[i][j]);
        } else {
          chmin(dp[i + 1][j], dp[i][j] + 1);
        }
      }

      if (j + 1 < w) {
        if (s[i][j + 1] == '.') {
          chmin(dp[i][j + 1], dp[i][j]);
        } else {
          chmin(dp[i][j + 1], dp[i][j] + 1);
        }
      }
    } else {
      if (i + 1 < h) {
        if (s[i + 1][j] == '.') {
          chmin(dp[i + 1][j], dp[i][j]);
        } else {
          chmin(dp[i + 1][j], dp[i][j]);
        }
      }

      if (j + 1 < w) {
        if (s[i][j + 1] == '.') {
          chmin(dp[i][j + 1], dp[i][j]);
        } else {
          chmin(dp[i][j + 1], dp[i][j]);
        }
      }
    }
  }
  cout << dp[h - 1][w - 1] << endl;
}

signed main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(15);
  Main();
  return 0;
}