Problem p02644 (C++) — buggy submission, verdict: Time Limit Exceeded

#define DEBUG 0
/**
 * File    : F2.cpp
 * Author  : Kazune Takahashi
 * Created : 6/15/2020, 11:46:33 PM
 * Powered by Visual Studio Code
 */
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>
// ----- boost -----
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>
// ----- using directives and manipulations -----
using namespace std;
using boost::rational;
using boost::multiprecision::cpp_int;
using ll = long long;
using ld = long double;
template <typename T> using max_heap = priority_queue<T>;
template <typename T> using min_heap = priority_queue<T, vector<T>, greater<T>>;
// ----- constexpr for Mint and Combination -----
constexpr ll MOD{1'000'000'007LL};
// constexpr ll MOD{998'244'353LL}; // be careful
constexpr ll MAX_SIZE{3'000'010LL};
// constexpr ll MAX_SIZE{30'000'010LL}; // if 10^7 is needed
// ----- ch_max and ch_min -----
template <typename T> bool ch_max(T &left, T right) {
  if (left < right) {
    left = right;
    return true;
  }
  return false;
}
template <typename T> bool ch_min(T &left, T right) {
  if (left > right) {
    left = right;
    return true;
  }
  return false;
}
// ----- Mint -----
template <ll MOD = MOD> class Mint {
public:
  ll x;
  Mint() : x{0LL} {}
  Mint(ll x) : x{(x % MOD + MOD) % MOD} {}
  Mint operator-() const { return x ? MOD - x : 0; }
  Mint &operator+=(Mint const &a) {
    if ((x += a.x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  Mint &operator-=(Mint const &a) { return *this += -a; }
  Mint &operator++() { return *this += 1; }
  Mint operator++(int) {
    Mint tmp{*this};
    ++*this;
    return tmp;
  }
  Mint &operator--() { return *this -= 1; }
  Mint operator--(int) {
    Mint tmp{*this};
    --*this;
    return tmp;
  }
  Mint &operator*=(Mint const &a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  Mint &operator/=(Mint const &a) {
    Mint b{a};
    return *this *= b.power(MOD - 2);
  }
  Mint operator+(Mint const &a) const { return Mint(*this) += a; }
  Mint operator-(Mint const &a) const { return Mint(*this) -= a; }
  Mint operator*(Mint const &a) const { return Mint(*this) *= a; }
  Mint operator/(Mint const &a) const { return Mint(*this) /= a; }
  bool operator<(Mint const &a) const { return x < a.x; }
  bool operator<=(Mint const &a) const { return x <= a.x; }
  bool operator>(Mint const &a) const { return x > a.x; }
  bool operator>=(Mint const &a) const { return x >= a.x; }
  bool operator==(Mint const &a) const { return x == a.x; }
  bool operator!=(Mint const &a) const { return !(*this == a); }
  Mint power(ll N) const {
    if (N == 0) {
      return 1;
    } else if (N % 2 == 1) {
      return *this * power(N - 1);
    } else {
      Mint half = power(N / 2);
      return half * half;
    }
  }
};
template <ll MOD> Mint<MOD> operator+(ll lhs, Mint<MOD> const &rhs) {
  return rhs + lhs;
}
template <ll MOD> Mint<MOD> operator-(ll lhs, Mint<MOD> const &rhs) {
  return -rhs + lhs;
}
template <ll MOD> Mint<MOD> operator*(ll lhs, Mint<MOD> const &rhs) {
  return rhs * lhs;
}
template <ll MOD> Mint<MOD> operator/(ll lhs, Mint<MOD> const &rhs) {
  return Mint<MOD>{lhs} / rhs;
}
template <ll MOD> istream &operator>>(istream &stream, Mint<MOD> &a) {
  return stream >> a.x;
}
template <ll MOD> ostream &operator<<(ostream &stream, Mint<MOD> const &a) {
  return stream << a.x;
}
// ----- Combination -----
template <ll MOD = MOD, ll MAX_SIZE = MAX_SIZE> class Combination {
public:
  vector<Mint<MOD>> inv, fact, factinv;
  Combination() : inv(MAX_SIZE), fact(MAX_SIZE), factinv(MAX_SIZE) {
    inv[1] = 1;
    for (auto i{2LL}; i < MAX_SIZE; i++) {
      inv[i] = (-inv[MOD % i]) * (MOD / i);
    }
    fact[0] = factinv[0] = 1;
    for (auto i{1LL}; i < MAX_SIZE; i++) {
      fact[i] = Mint<MOD>(i) * fact[i - 1];
      factinv[i] = inv[i] * factinv[i - 1];
    }
  }
  Mint<MOD> operator()(int n, int k) {
    if (n >= 0 && k >= 0 && n - k >= 0) {
      return fact[n] * factinv[k] * factinv[n - k];
    }
    return 0;
  }
  Mint<MOD> catalan(int x, int y) {
    return (*this)(x + y, y) - (*this)(x + y, y - 1);
  }
};
// ----- for C++14 -----
using mint = Mint<MOD>;
using combination = Combination<MOD, MAX_SIZE>;
template <typename T> T gcd(T x, T y) { return y ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }
// ----- for C++17 -----
template <typename T>
int popcount(T x) // C++20
{
  int ans{0};
  while (x != 0) {
    ans += x & 1;
    x >>= 1;
  }
  return ans;
}
// ----- Infty -----
template <typename T> constexpr T Infty() { return numeric_limits<T>::max(); }
template <typename T> constexpr T mInfty() { return numeric_limits<T>::min(); }
// ----- frequently used constexpr -----
// constexpr double epsilon{1e-10};
// constexpr ll infty{1'000'000'000'000'010LL}; // or
// constexpr int infty{1'000'000'010};
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};
// ----- Yes() and No() -----
void Yes() {
  cout << "Yes" << endl;
  exit(0);
}
void No() {
  cout << "No" << endl;
  exit(0);
}

// ----- 2D, 3D, 4D vectors -----
// Referring to ymatsux-san's source code:
// https://atcoder.jp/contests/abc138/submissions/7018300

template <typename T>
vector<vector<T>> Make2DVector(size_t d0, size_t d1, T v = T{}) {
  return vector<vector<T>>(d0, vector<T>(d1, v));
}

template <typename T>
vector<vector<vector<T>>> Make3DVector(size_t d0, size_t d1, size_t d2,
                                       T v = T{}) {
  return vector<vector<vector<T>>>(d0, Make2DVector(d1, d2, v));
}

template <typename T>
vector<vector<vector<vector<T>>>> Make4DVector(size_t d0, size_t d1, size_t d2,
                                               size_t d3, T v = T{}) {
  return vector<vector<vector<vector<T>>>>(d0, Make3DVector(d1, d2, d3, v));
}

// ----- Solve -----

using Point = tuple<int, int>;

class Solve {
  int H, W, K;
  vector<vector<int>> V;
  int sx, sy, gx, gy;

public:
  Solve(int H, int W) : H{H}, W{W}, V{Make2DVector(H, W, Infty<int>())} {
    cin >> K;
    cin >> sx >> sy >> gx >> gy;
    --sx;
    --sy;
    --gx;
    --gy;
    for (auto i{0}; i < H; ++i) {
      for (auto j{0}; j < W; ++j) {
        char c;
        cin >> c;
        if (c == '@') {
          V[i][j] = -1;
        }
      }
    }
  }

  void flush() {
    queue<Point> Q;
    Q.push(Point{sx, sy});
    V[sx][sy] = 0;
    while (!Q.empty()) {
      auto p{Q.front()};
      auto [x, y] = p;
      Q.pop();
      for (auto k{0}; k < 4; ++k) {
        for (auto i{1}; i <= K; ++i) {
          auto nx{x + dx[k] * i};
          auto ny{y + dy[k] * i};
          if (!valid(nx, ny)) {
            break;
          } else if (V[nx][ny] == Infty<int>()) {
            V[nx][ny] = V[x][y] + 1;
            Q.push(Point{nx, ny});
          } else if (V[nx][ny] == V[x][y] + 1) {
            continue;
          } else {
            break;
          }
        }
      }
    }
    auto ans{V[gx][gy]};
    if (ans == Infty<int>()) {
      cout << -1 << endl;
    } else {
      cout << ans << endl;
    }
  }

private:
  bool valid(int x, int y) {
    return 0 <= x && x < H && 0 <= y && y < W && V[x][y] != -1;
  }
};

// ----- main() -----

int main() {
  int H, W;
  cin >> H >> W;
  Solve solve(H, W);
  solve.flush();
}


Error: TLE

Fixed submission:

#define DEBUG 0
/**
 * File    : F2.cpp
 * Author  : Kazune Takahashi
 * Created : 6/15/2020, 11:46:33 PM
 * Powered by Visual Studio Code
 */
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>
// ----- boost -----
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>
// ----- using directives and manipulations -----
using namespace std;
using boost::rational;
using boost::multiprecision::cpp_int;
using ll = long long;
using ld = long double;
template <typename T> using max_heap = priority_queue<T>;
template <typename T> using min_heap = priority_queue<T, vector<T>, greater<T>>;
// ----- constexpr for Mint and Combination -----
constexpr ll MOD{1'000'000'007LL};
// constexpr ll MOD{998'244'353LL}; // be careful
constexpr ll MAX_SIZE{3'000'010LL};
// constexpr ll MAX_SIZE{30'000'010LL}; // if 10^7 is needed
// ----- ch_max and ch_min -----
template <typename T> bool ch_max(T &left, T right) {
  if (left < right) {
    left = right;
    return true;
  }
  return false;
}
template <typename T> bool ch_min(T &left, T right) {
  if (left > right) {
    left = right;
    return true;
  }
  return false;
}
// ----- Mint -----
template <ll MOD = MOD> class Mint {
public:
  ll x;
  Mint() : x{0LL} {}
  Mint(ll x) : x{(x % MOD + MOD) % MOD} {}
  Mint operator-() const { return x ? MOD - x : 0; }
  Mint &operator+=(Mint const &a) {
    if ((x += a.x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  Mint &operator-=(Mint const &a) { return *this += -a; }
  Mint &operator++() { return *this += 1; }
  Mint operator++(int) {
    Mint tmp{*this};
    ++*this;
    return tmp;
  }
  Mint &operator--() { return *this -= 1; }
  Mint operator--(int) {
    Mint tmp{*this};
    --*this;
    return tmp;
  }
  Mint &operator*=(Mint const &a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  Mint &operator/=(Mint const &a) {
    Mint b{a};
    return *this *= b.power(MOD - 2);
  }
  Mint operator+(Mint const &a) const { return Mint(*this) += a; }
  Mint operator-(Mint const &a) const { return Mint(*this) -= a; }
  Mint operator*(Mint const &a) const { return Mint(*this) *= a; }
  Mint operator/(Mint const &a) const { return Mint(*this) /= a; }
  bool operator<(Mint const &a) const { return x < a.x; }
  bool operator<=(Mint const &a) const { return x <= a.x; }
  bool operator>(Mint const &a) const { return x > a.x; }
  bool operator>=(Mint const &a) const { return x >= a.x; }
  bool operator==(Mint const &a) const { return x == a.x; }
  bool operator!=(Mint const &a) const { return !(*this == a); }
  Mint power(ll N) const {
    if (N == 0) {
      return 1;
    } else if (N % 2 == 1) {
      return *this * power(N - 1);
    } else {
      Mint half = power(N / 2);
      return half * half;
    }
  }
};
template <ll MOD> Mint<MOD> operator+(ll lhs, Mint<MOD> const &rhs) {
  return rhs + lhs;
}
template <ll MOD> Mint<MOD> operator-(ll lhs, Mint<MOD> const &rhs) {
  return -rhs + lhs;
}
template <ll MOD> Mint<MOD> operator*(ll lhs, Mint<MOD> const &rhs) {
  return rhs * lhs;
}
template <ll MOD> Mint<MOD> operator/(ll lhs, Mint<MOD> const &rhs) {
  return Mint<MOD>{lhs} / rhs;
}
template <ll MOD> istream &operator>>(istream &stream, Mint<MOD> &a) {
  return stream >> a.x;
}
template <ll MOD> ostream &operator<<(ostream &stream, Mint<MOD> const &a) {
  return stream << a.x;
}
// ----- Combination -----
template <ll MOD = MOD, ll MAX_SIZE = MAX_SIZE> class Combination {
public:
  vector<Mint<MOD>> inv, fact, factinv;
  Combination() : inv(MAX_SIZE), fact(MAX_SIZE), factinv(MAX_SIZE) {
    inv[1] = 1;
    for (auto i{2LL}; i < MAX_SIZE; i++) {
      inv[i] = (-inv[MOD % i]) * (MOD / i);
    }
    fact[0] = factinv[0] = 1;
    for (auto i{1LL}; i < MAX_SIZE; i++) {
      fact[i] = Mint<MOD>(i) * fact[i - 1];
      factinv[i] = inv[i] * factinv[i - 1];
    }
  }
  Mint<MOD> operator()(int n, int k) {
    if (n >= 0 && k >= 0 && n - k >= 0) {
      return fact[n] * factinv[k] * factinv[n - k];
    }
    return 0;
  }
  Mint<MOD> catalan(int x, int y) {
    return (*this)(x + y, y) - (*this)(x + y, y - 1);
  }
};
// ----- for C++14 -----
using mint = Mint<MOD>;
using combination = Combination<MOD, MAX_SIZE>;
template <typename T> T gcd(T x, T y) { return y ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }
// ----- for C++17 -----
template <typename T>
int popcount(T x) // C++20
{
  int ans{0};
  while (x != 0) {
    ans += x & 1;
    x >>= 1;
  }
  return ans;
}
// ----- Infty -----
template <typename T> constexpr T Infty() { return numeric_limits<T>::max(); }
template <typename T> constexpr T mInfty() { return numeric_limits<T>::min(); }
// ----- frequently used constexpr -----
// constexpr double epsilon{1e-10};
// constexpr ll infty{1'000'000'000'000'010LL}; // or
// constexpr int infty{1'000'000'010};
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};
// ----- Yes() and No() -----
void Yes() {
  cout << "Yes" << endl;
  exit(0);
}
void No() {
  cout << "No" << endl;
  exit(0);
}

// ----- 2D, 3D, 4D vectors -----
// Referring to ymatsux-san's source code:
// https://atcoder.jp/contests/abc138/submissions/7018300

template <typename T>
vector<vector<T>> Make2DVector(size_t d0, size_t d1, T v = T{}) {
  return vector<vector<T>>(d0, vector<T>(d1, v));
}

template <typename T>
vector<vector<vector<T>>> Make3DVector(size_t d0, size_t d1, size_t d2,
                                       T v = T{}) {
  return vector<vector<vector<T>>>(d0, Make2DVector(d1, d2, v));
}

template <typename T>
vector<vector<vector<vector<T>>>> Make4DVector(size_t d0, size_t d1, size_t d2,
                                               size_t d3, T v = T{}) {
  return vector<vector<vector<vector<T>>>>(d0, Make3DVector(d1, d2, d3, v));
}

// ----- Solve -----

using Point = tuple<int, int>;

class Solve {
  int H, W, K;
  vector<vector<int>> V;
  int sx, sy, gx, gy;

public:
  Solve(int H, int W) : H{H}, W{W}, V{Make2DVector(H, W, Infty<int>())} {
    cin >> K;
    cin >> sx >> sy >> gx >> gy;
    --sx;
    --sy;
    --gx;
    --gy;
    for (auto i{0}; i < H; ++i) {
      for (auto j{0}; j < W; ++j) {
        char c;
        cin >> c;
        if (c == '@') {
          V[i][j] = -1;
        }
      }
    }
  }

  void flush() {
    queue<Point> Q;
    Q.push(Point{sx, sy});
    V[sx][sy] = 0;
    while (!Q.empty()) {
      auto p{Q.front()};
      auto [x, y] = p;
      Q.pop();
      for (auto k{0}; k < 4; ++k) {
        for (auto i{1}; i <= K; ++i) {
          auto nx{x + dx[k] * i};
          auto ny{y + dy[k] * i};
          if (!valid(nx, ny)) {
            break;
          } else if (V[nx][ny] == Infty<int>()) {
            V[nx][ny] = V[x][y] + 1;
            Q.push(Point{nx, ny});
          } else if (V[nx][ny] <= V[x][y] + 1) {
            continue;
          }
        }
      }
    }
    auto ans{V[gx][gy]};
    if (ans == Infty<int>()) {
      cout << -1 << endl;
    } else {
      cout << ans << endl;
    }
  }

private:
  bool valid(int x, int y) {
    return 0 <= x && x < H && 0 <= y && y < W && V[x][y] != -1;
  }
};

// ----- main() -----

int main() {
  int H, W;
  cin >> H >> W;
  Solve solve(H, W);
  solve.flush();
}