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

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

typedef long long int lli;
#define int lli
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<lli> vli;
typedef vector<pii> vii;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    OrderedSet;

const int MOD = 1e9 + 7;
const double PI = acos(-1.0);

#define fastio                                                                 \\
  ios_base::sync_with_stdio(0);                                                \\
  cin.tie(0)
#define sz(a) int((a).size())
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define all(c) (c).begin(), (c).end()
#define present(c, x) ((c).find(x) != (c).end())
#define cpresent(c, x) (find(all(c), x) != (c).end())
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repA(i, a, n) for (int i = a; i <= (n); ++i)
#define repD(i, a, n) for (int i = a; i >= (n); --i)
#define endl "\\n"
#define error(x) cerr << #x << " = " << (x) << endl
#define errorp(p) cerr << #p << " = " << (p.first) << ", " << (p.second) << endl

template <typename T> T gcd(T a, T b) { return (b ? __gcd(a, b) : a); }
template <typename T> T lcm(T a, T b) { return (a * b) / gcd(a, b); }

int N;

void childs(int num, vi &child) {
  int row = num / N;
  int col = num % N;
  if (row > 0) {
    child.pb((row - 1) * N + col);
  }
  if (row < N - 1) {
    child.pb((row + 1) * N + col);
  }
  if (col > 0) {
    child.pb(row * N + col - 1);
  }
  if (col < N - 1) {
    child.pb(row * N + col + 1);
  }
}

signed main() {
#ifdef DEBUG
  freopen("test", "r", stdin);
#endif
  fastio;

  cin >> N;
  int n2 = N * N;
  vi perm(n2);
  rep(i, n2) {
    cin >> perm[i];
    perm[i]--;
  }

  vi paths(n2);
  rep(i, n2) {
    int row = i / N;
    int col = i % N;
    paths[i] = min({row, N - 1 - row, col, N - 1 - col});
  }

  int ans = 0;
  vi vals(n2, 1);

  queue<int> q;
  for (auto p : perm) {
    ans += paths[p];
    vals[p] = 0;
    q.push(p);
    while (!q.empty()) {
      int x = q.front();
      q.pop();
      vi child;
      childs(x, child);
      for (auto c : child) {
        if (paths[c] > vals[x] + paths[x]) {
          paths[c] = vals[x] + paths[x];
          q.push(c);
        }
      }
    }
  }

  cout << ans << endl;

  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

typedef long long int lli;
#define int lli
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<lli> vli;
typedef vector<pii> vii;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    OrderedSet;

const int MOD = 1e9 + 7;
const double PI = acos(-1.0);

#define fastio                                                                 \\
  ios_base::sync_with_stdio(0);                                                \\
  cin.tie(0)
#define sz(a) int((a).size())
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define all(c) (c).begin(), (c).end()
#define present(c, x) ((c).find(x) != (c).end())
#define cpresent(c, x) (find(all(c), x) != (c).end())
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repA(i, a, n) for (int i = a; i <= (n); ++i)
#define repD(i, a, n) for (int i = a; i >= (n); --i)
#define endl "\\n"
#define error(x) cerr << #x << " = " << (x) << endl
#define errorp(p) cerr << #p << " = " << (p.first) << ", " << (p.second) << endl

template <typename T> T gcd(T a, T b) { return (b ? __gcd(a, b) : a); }
template <typename T> T lcm(T a, T b) { return (a * b) / gcd(a, b); }

int N;

void childs(int num, vi &child) {
  int row = num / N;
  int col = num % N;
  if (row > 0) {
    child.pb((row - 1) * N + col);
  }
  if (row < N - 1) {
    child.pb((row + 1) * N + col);
  }
  if (col > 0) {
    child.pb(row * N + col - 1);
  }
  if (col < N - 1) {
    child.pb(row * N + col + 1);
  }
}

signed main() {
#ifdef DEBUG
  freopen("test", "r", stdin);
#endif
  fastio;

  cin >> N;
  int n2 = N * N;
  vi perm(n2);
  rep(i, n2) {
    cin >> perm[i];
    perm[i]--;
  }

  vi paths(n2);
  rep(i, n2) {
    int row = i / N;
    int col = i % N;
    paths[i] = min({row, N - 1 - row, col, N - 1 - col});
  }

  int ans = 0;
  vi vals(n2, 1);

  queue<int> q;
  for (auto p : perm) {
    ans += paths[p];
    vals[p] = 0;
    vector<bool> visited(n2);
    q.push(p);
    visited[p] = true;
    while (!q.empty()) {
      int x = q.front();
      q.pop();
      vi child;
      childs(x, child);
      for (auto c : child) {
        if (!visited[c]) {
          if (paths[c] > vals[x] + paths[x]) {
            paths[c] = vals[x] + paths[x];
            visited[c] = true;
            q.push(c);
          }
        }
      }
    }
  }

  cout << ans << endl;

  return 0;
}