Problem p02670 (C++) — buggy submission, verdict: Time Limit Exceeded

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

#define LL long long
// #define LL __int64
typedef pair<int, int> pii;
typedef pair<LL, LL> pLL;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;

template <typename T> inline void read(T &x) {
  static char _c;
  static bool _f;

  x = 0;
  _f = 0;
  _c = getchar();

  while (_c < '0' || '9' < _c) {
    if (_c == '-')
      _f = true;
    _c = getchar();
  }
  while ('0' <= _c && _c <= '9') {
    x = (x << 1) + (x << 3) + (_c & 15);
    _c = getchar();
  }
  if (_f)
    x = -x;
}
template <typename T, typename... Args> inline void read(T &x, Args &...args) {
  read(x);
  read(args...);
}

template <typename T> inline void Min(T &x, T y) {
  if (y < x)
    x = y;
}
template <typename T> inline void Max(T &x, T y) {
  if (x < y)
    x = y;
}

#define lowbit(x) ((x) & -(x))
#define lson l, mid, id << 1
#define rson mid + 1, r, id << 1 | 1
#define ls id << 1
#define rs id << 1 | 1
#define MID(l, r) ((l) + (((r) - (l)) >> 1))
#define fi first
#define se second
#define mk make_pair
#define mt make_tuple
#define pb push_back
#define all(a) a.begin(), a.end()

const int INF = 0x3f3f3f3f;
const LL LINF = 0x3f3f3f3f3f3f3f3f;
const double pi = (double)acos(-1.0);
const double eps = (double)1e-8;
const int e5 = (int)1e5 + 5;
// const int MOD = (int) 1e9 + 7;
const int MOD = (int)1000000007;
// const int MOD = 998244353;

template <typename T0, typename T1>
inline void depair(T0 &x, T1 &y, pair<T0, T1> &p) {
  x = p.fi, y = p.se;
}
inline int sig(double x) { return x < -eps ? -1 : eps < x; }
LL fp(LL a, LL n, LL mod = MOD) {
  if (n < 0)
    a = fp(a, mod - 2, mod), n = -n;
  LL res = 1;
  for (; n; n >>= 1, a = a * a % mod)
    if (n & 1)
      res = res * a % mod;
  return res;
}

struct Mint {
  int x;
  Mint() { x = 0; }
  Mint(int _x) : x(_x) {
    if (x < 0 || x >= MOD)
      x = (x % MOD + MOD) % MOD;
  }
  Mint(LL _x) : x(_x) {
    if (x < 0 || x >= MOD)
      x = (x % MOD + MOD) % MOD;
  }
  Mint operator-() const { return Mint(MOD - x); }
  Mint operator+(const Mint &rhs) const {
    return Mint(x + rhs.x >= MOD ? x + rhs.x - MOD : x + rhs.x);
  }
  Mint operator-(const Mint &rhs) const {
    return Mint(x - rhs.x < 0 ? x - rhs.x + MOD : x - rhs.x);
  }
  Mint operator*(const Mint &rhs) const { return Mint((LL)x * rhs.x % MOD); }
  Mint operator/(const Mint &rhs) const {
    return Mint(x * fp(rhs.x, -1) % MOD);
  }
  Mint &operator+=(const Mint &rhs) {
    x += rhs.x;
    if (x >= MOD)
      x -= MOD;
    return *this;
  }
  Mint &operator*=(const Mint &rhs) {
    x = ((LL)x * rhs.x) % MOD;
    return *this;
  }
  bool operator==(const Mint &rhs) const { return x == rhs.x; }
  bool operator!=(const Mint &rhs) const { return x != rhs.x; }
  friend ostream &operator<<(ostream &out, const Mint &rhs) {
    return out << rhs.x;
  }
  friend istream &operator>>(istream &in, Mint &rhs) { return in >> rhs.x; }
};

const int maxn = (int)2e5 + 20;
const int maxm = (int)1e6 + 20;

void work() {
  int n;
  cin >> n;
  int nn = n * n;

  VVI vis(n, VI(n, 0));
  VVI dis(n, VI(n));
  VVI r(n, VI(n, 1));

  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++)
      dis[i][j] = min({i, n - 1 - i, j, n - 1 - j});

  VI dx({0, 0, 1, -1});
  VI dy({1, -1, 0, 0});

  int ans = 0;
  for (int i = 0; i < nn; i++) {
    int p;
    read(p);
    p--;
    int x = p / n, y = p % n;
    ans += dis[x][y];
    r[x][y] = 0;
    queue<pii> Q;
    Q.emplace(mk(x, y));

    while (!Q.empty()) {
      int px = Q.front().fi;
      int py = Q.front().se;
      Q.pop();

      for (int i = 0; i < 4; i++) {
        int nx = px + dx[i];
        int ny = py + dy[i];

        if (0 <= nx && nx < n && 0 <= ny && ny < n) {
          if (dis[px][py] + r[px][py] < dis[nx][ny]) {
            dis[nx][ny] = dis[px][py] + r[px][py];
            Q.emplace(mk(nx, ny));
          }
        }
      }
    }
  }
  cout << ans << endl;
}

int main(int argc, char **argv) {
#ifdef yukihana0416
  freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#endif // yukihana0416
       //    get_prime();
       //    pre();
  int tc = 1;
  //    read(tc);
  for (int ca = 1; ca <= tc; ca++) {
    //        printf("Case #%d: ", ca);
    work();
  }
  return 0;
}


Error: TLE

Fixed submission:

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

#define LL long long
// #define LL __int64
typedef pair<int, int> pii;
typedef pair<LL, LL> pLL;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;

template <typename T> inline void read(T &x) {
  static char _c;
  static bool _f;

  x = 0;
  _f = 0;
  _c = getchar();

  while (_c < '0' || '9' < _c) {
    if (_c == '-')
      _f = true;
    _c = getchar();
  }
  while ('0' <= _c && _c <= '9') {
    x = (x << 1) + (x << 3) + (_c & 15);
    _c = getchar();
  }
  if (_f)
    x = -x;
}
template <typename T, typename... Args> inline void read(T &x, Args &...args) {
  read(x);
  read(args...);
}

template <typename T> inline void Min(T &x, T y) {
  if (y < x)
    x = y;
}
template <typename T> inline void Max(T &x, T y) {
  if (x < y)
    x = y;
}

#define lowbit(x) ((x) & -(x))
#define lson l, mid, id << 1
#define rson mid + 1, r, id << 1 | 1
#define ls id << 1
#define rs id << 1 | 1
#define MID(l, r) ((l) + (((r) - (l)) >> 1))
#define fi first
#define se second
#define mk make_pair
#define mt make_tuple
#define pb push_back
#define all(a) a.begin(), a.end()

const int INF = 0x3f3f3f3f;
const LL LINF = 0x3f3f3f3f3f3f3f3f;
const double pi = (double)acos(-1.0);
const double eps = (double)1e-8;
const int e5 = (int)1e5 + 5;
// const int MOD = (int) 1e9 + 7;
const int MOD = (int)1000000007;
// const int MOD = 998244353;

template <typename T0, typename T1>
inline void depair(T0 &x, T1 &y, pair<T0, T1> &p) {
  x = p.fi, y = p.se;
}
inline int sig(double x) { return x < -eps ? -1 : eps < x; }
LL fp(LL a, LL n, LL mod = MOD) {
  if (n < 0)
    a = fp(a, mod - 2, mod), n = -n;
  LL res = 1;
  for (; n; n >>= 1, a = a * a % mod)
    if (n & 1)
      res = res * a % mod;
  return res;
}

struct Mint {
  int x;
  Mint() { x = 0; }
  Mint(int _x) : x(_x) {
    if (x < 0 || x >= MOD)
      x = (x % MOD + MOD) % MOD;
  }
  Mint(LL _x) : x(_x) {
    if (x < 0 || x >= MOD)
      x = (x % MOD + MOD) % MOD;
  }
  Mint operator-() const { return Mint(MOD - x); }
  Mint operator+(const Mint &rhs) const {
    return Mint(x + rhs.x >= MOD ? x + rhs.x - MOD : x + rhs.x);
  }
  Mint operator-(const Mint &rhs) const {
    return Mint(x - rhs.x < 0 ? x - rhs.x + MOD : x - rhs.x);
  }
  Mint operator*(const Mint &rhs) const { return Mint((LL)x * rhs.x % MOD); }
  Mint operator/(const Mint &rhs) const {
    return Mint(x * fp(rhs.x, -1) % MOD);
  }
  Mint &operator+=(const Mint &rhs) {
    x += rhs.x;
    if (x >= MOD)
      x -= MOD;
    return *this;
  }
  Mint &operator*=(const Mint &rhs) {
    x = ((LL)x * rhs.x) % MOD;
    return *this;
  }
  bool operator==(const Mint &rhs) const { return x == rhs.x; }
  bool operator!=(const Mint &rhs) const { return x != rhs.x; }
  friend ostream &operator<<(ostream &out, const Mint &rhs) {
    return out << rhs.x;
  }
  friend istream &operator>>(istream &in, Mint &rhs) { return in >> rhs.x; }
};

const int maxn = (int)2e5 + 20;
const int maxm = (int)1e6 + 20;

void work() {
  int n;
  cin >> n;
  int nn = n * n;

  VVI vis(n, VI(n, 0));
  VVI dis(n, VI(n));
  VVI r(n, VI(n, 1));

  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++)
      dis[i][j] = min({i, n - 1 - i, j, n - 1 - j});

  VI dx({0, 0, 1, -1});
  VI dy({1, -1, 0, 0});

  int ans = 0;
  for (int i = 0; i < nn; i++) {
    int p;
    cin >> p;
    p--;
    int x = p / n, y = p % n;
    ans += dis[x][y];
    r[x][y] = 0;
    VVI inq(n, VI(n, 0));
    queue<pair<int, int>> Q;

    Q.push(mk(x, y));
    inq[x][y] = 1;

    while (Q.size()) {
      int px = Q.front().fi;
      int py = Q.front().se;
      Q.pop();
      inq[px][py] = 0;

      for (int i = 0; i < 4; i++) {
        int nx = px + dx[i];
        int ny = py + dy[i];

        if (0 <= nx && nx < n && 0 <= ny && ny < n) {
          if (dis[px][py] + r[px][py] < dis[nx][ny]) {
            dis[nx][ny] = dis[px][py] + r[px][py];
            if (!inq[nx][ny]) {
              inq[nx][ny] = 1;
              Q.push(mk(nx, ny));
            }
          }
        }
      }
    }
  }
  cout << ans << endl;
}

int main(int argc, char **argv) {
#ifdef yukihana0416
  freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#endif // yukihana0416
       //    get_prime();
       //    pre();
  int tc = 1;
  //    read(tc);
  for (int ca = 1; ca <= tc; ca++) {
    //        printf("Case #%d: ", ca);
    work();
  }
  return 0;
}