Problem p03053 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define countof(array) (sizeof(array) / sizeof(array[0]))
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define srep(i, n, s) for (int i = s; i < (n); ++i)
#define rsrep(i, n, s) for (int i = (n)-1; i >= s; --i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define aall(a) (a), (a) + countof(a) // for array sorting
#define raall(a) (a), (a) + countof(a), greater<>()
#define show(x) cout << #x << " = " << x << endl;
#define vfind(v, a) find(all(v), a) != v.end()
#define yn(f)                                                                  \
  {                                                                            \
    if (f)                                                                     \
      puts("YES");                                                             \
    else                                                                       \
      puts("NO");                                                              \
  }
#define yns(f)                                                                 \
  {                                                                            \
    if (f)                                                                     \
      puts("Yes");                                                             \
    else                                                                       \
      puts("No");                                                              \
  }
#define show_ary(...)                                                          \
  {                                                                            \
    cout << #__VA_ARGS__ << " = ";                                             \
    for (const auto &x : (__VA_ARGS__)) {                                      \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define show_pair(...)                                                         \
  cout << #__VA_ARGS__ << " = " << endl;                                       \
  for (const auto &x : (__VA_ARGS__)) {                                        \
    cout << "  " << x.fi << " : " << x.se << endl;                             \
  }
#define out_ary(...)                                                           \
  {                                                                            \
    for (const auto &x : (__VA_ARGS__)) {                                      \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define argmax(v) distance((v).begin(), max_element(all(v)))
#define argmin(v) distance((v).begin(), min_element(all(v)))
#define vmax(v) *max_element(all(v))
#define vmin(v) *min_element(all(v))
typedef long long int ll;
typedef pair<int, int> P;
typedef vector<P> vpair;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef vector<double> vdouble;
typedef vector<string> vstr;
typedef vector<bool> vbool;
typedef vector<vint> vvint;
typedef vector<vll> vvll;
typedef vector<vstr> vvstr;
typedef vector<vbool> vvbool;
const ll LINF = 2000000000000000000ll;
const int INF = 1000000100;
const ll MOD = 1e9 + 7;

int h, w;
vstr a;
vint dx = {1, 0, -1, 0};
vint dy = {0, 1, 0, -1};

vvint bfs(vvint d, int x, int y) {
  queue<P> que;
  que.push(P(x, y));
  d[x][y] = 0;

  while (que.size()) {
    P p = que.front();
    que.pop();
    if (a[p.fi][p.se] == '#')
      d[p.fi][p.se] = 0;
    rep(i, 4) {
      int nx = p.fi + dx[i], ny = p.se + dy[i];

      if (0 <= nx && nx < h && 0 <= ny && ny < w &&
          d[nx][ny] > d[p.fi][p.se] + 1) {
        que.push(P(nx, ny));
        d[nx][ny] = d[p.fi][p.se] + 1;
      }
    }
  }

  return d;
}

int main() {
  cin >> h >> w;
  a.resize(h);
  rep(i, h) { cin >> a[i]; }
  int mx = 0;
  vvint d(h, vint(w, INF));
  rep(i, h) {
    rep(j, w) {
      if (a[i][j] == '.')
        continue;
      else {
        d = bfs(d, i, j);
      }
    }
  }
  rep(i, h) mx = max(mx, vmax(d[i]));
  ;

  int ans = mx;

  cout << ans << endl;
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define countof(array) (sizeof(array) / sizeof(array[0]))
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define srep(i, n, s) for (int i = s; i < (n); ++i)
#define rsrep(i, n, s) for (int i = (n)-1; i >= s; --i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define aall(a) (a), (a) + countof(a) // for array sorting
#define raall(a) (a), (a) + countof(a), greater<>()
#define show(x) cout << #x << " = " << x << endl;
#define vfind(v, a) find(all(v), a) != v.end()
#define yn(f)                                                                  \
  {                                                                            \
    if (f)                                                                     \
      puts("YES");                                                             \
    else                                                                       \
      puts("NO");                                                              \
  }
#define yns(f)                                                                 \
  {                                                                            \
    if (f)                                                                     \
      puts("Yes");                                                             \
    else                                                                       \
      puts("No");                                                              \
  }
#define show_ary(...)                                                          \
  {                                                                            \
    cout << #__VA_ARGS__ << " = ";                                             \
    for (const auto &x : (__VA_ARGS__)) {                                      \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define show_pair(...)                                                         \
  cout << #__VA_ARGS__ << " = " << endl;                                       \
  for (const auto &x : (__VA_ARGS__)) {                                        \
    cout << "  " << x.fi << " : " << x.se << endl;                             \
  }
#define out_ary(...)                                                           \
  {                                                                            \
    for (const auto &x : (__VA_ARGS__)) {                                      \
      cout << x << " ";                                                        \
    }                                                                          \
    cout << endl;                                                              \
  }
#define argmax(v) distance((v).begin(), max_element(all(v)))
#define argmin(v) distance((v).begin(), min_element(all(v)))
#define vmax(v) *max_element(all(v))
#define vmin(v) *min_element(all(v))
typedef long long int ll;
typedef pair<int, int> P;
typedef vector<P> vpair;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef vector<double> vdouble;
typedef vector<string> vstr;
typedef vector<bool> vbool;
typedef vector<vint> vvint;
typedef vector<vll> vvll;
typedef vector<vstr> vvstr;
typedef vector<vbool> vvbool;
const ll LINF = 2000000000000000000ll;
const int INF = 1000000100;
const ll MOD = 1e9 + 7;

int h, w;
vstr a;
vint dx = {1, 0, -1, 0};
vint dy = {0, 1, 0, -1};

vvint bfs(vvint d, int x, int y) {
  queue<P> que;
  que.push(P(x, y));
  d[x][y] = 0;

  while (que.size()) {
    P p = que.front();
    que.pop();
    if (a[p.fi][p.se] == '#')
      d[p.fi][p.se] = 0;
    rep(i, 4) {
      int nx = p.fi + dx[i], ny = p.se + dy[i];

      if (0 <= nx && nx < h && 0 <= ny && ny < w &&
          d[nx][ny] > d[p.fi][p.se] + 1) {
        que.push(P(nx, ny));
        d[nx][ny] = d[p.fi][p.se] + 1;
      }
    }
  }

  return d;
}

int main() {
  cin >> h >> w;
  a.resize(h);
  rep(i, h) { cin >> a[i]; }
  int mx = 0;
  vvint d(h, vint(w, INF));
  rep(i, h) {
    rep(j, w) {
      if (a[i][j] == '.')
        continue;
      else {
        d = bfs(d, i, j);
        break;
      }
    }
  }
  rep(i, h) mx = max(mx, vmax(d[i]));
  ;

  int ans = mx;

  cout << ans << endl;
  return 0;
}