Problem p02892 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define ADD(a, b) a = (a + ll(b)) % mod
#define MUL(a, b) a = (a * ll(b)) % mod
#define MAX(a, b) a = max(a, b)
#define MIN(a, b) a = min(a, b)
#define rep(i, a, b) for (int i = int(a); i < int(b); i++)
#define rer(i, a, b) for (int i = int(a) - 1; i >= int(b); i--)
#define all(a) (a).begin(), (a).end()
#define sz(v) (int)(v).size()
#define pb push_back
#define sec second
#define fst first
#define debug(fmt, ...) Debug(__LINE__, ":", fmt, ##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<int, pi> ppi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> mat;
typedef complex<double> comp;
void Debug() { cerr << '\n'; }
template <class FIRST, class... REST> void Debug(FIRST arg, REST... rest) {
  cerr << arg << " ";
  Debug(rest...);
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &v) {
  out << "[";
  if (!v.empty()) {
    rep(i, 0, sz(v) - 1) out << v[i] << ", ";
    out << v.back();
  }
  out << "]";
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &v) {
  out << "(" << v.first << ", " << v.second << ")";
  return out;
}
const int MAX_N = 500010;
const int MAX_V = 100010;
const double eps = 1e-6;
const ll mod = 1000000007;
const int inf = (1 << 30) - 1;
const ll linf = 1LL << 60;
const double PI = 3.14159265358979323846;
mt19937 rng; // use it by rng() % mod, shuffle(all(vec), rng)
///////////////////////////////////////////////////////////////////////////////////////////////////

int N;
vector<int> G[210];
int d[110];

void solve() {
  cin >> N;
  rep(i, 0, N) {
    rep(j, 0, N) {
      char a;
      cin >> a;
      if (a == '1')
        G[i].pb(j);
    }
  }
  int res = 0;
  rep(q, 0, N) {
    fill(d, d + N, inf);
    d[q] = 0;
    queue<int> que;
    que.push(q);
    while (!que.empty()) {
      int v = que.front();
      que.pop();
      rep(i, 0, sz(G[v])) {
        int n = G[v][i];
        if (d[n] == inf) {
          d[n] = d[v] + 1;
          que.push(n);
        } else {
          if (d[n] % 2 == d[v] % 2) {
            cout << -1 << "\n";
            return;
          }
        }
      }
    }
    rep(i, 0, N) { MAX(res, d[i] + 1); }
  }
  cout << res << "\n";
}

uint32_t rd() {
  uint32_t res;
#ifdef __MINGW32__
  asm volatile("rdrand %0" : "=a"(res)::"cc");
#else
  res = std::random_device()();
#endif
  return res;
}

int main() {
#ifndef LOCAL
  ios::sync_with_stdio(false);
  cin.tie(0);
#endif
  cout << fixed;
  cout.precision(20);
  cerr << fixed;
  cerr.precision(6);
  rng.seed(rd());
#ifdef LOCAL
  // freopen("in.txt", "wt", stdout); //for tester
  if (!freopen("in.txt", "rt", stdin))
    return 1;
#endif
  solve();
  cerr << "Time: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define ADD(a, b) a = (a + ll(b)) % mod
#define MUL(a, b) a = (a * ll(b)) % mod
#define MAX(a, b) a = max(a, b)
#define MIN(a, b) a = min(a, b)
#define rep(i, a, b) for (int i = int(a); i < int(b); i++)
#define rer(i, a, b) for (int i = int(a) - 1; i >= int(b); i--)
#define all(a) (a).begin(), (a).end()
#define sz(v) (int)(v).size()
#define pb push_back
#define sec second
#define fst first
#define debug(fmt, ...) Debug(__LINE__, ":", fmt, ##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<int, pi> ppi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> mat;
typedef complex<double> comp;
void Debug() { cerr << '\n'; }
template <class FIRST, class... REST> void Debug(FIRST arg, REST... rest) {
  cerr << arg << " ";
  Debug(rest...);
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &v) {
  out << "[";
  if (!v.empty()) {
    rep(i, 0, sz(v) - 1) out << v[i] << ", ";
    out << v.back();
  }
  out << "]";
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &v) {
  out << "(" << v.first << ", " << v.second << ")";
  return out;
}
const int MAX_N = 500010;
const int MAX_V = 100010;
const double eps = 1e-6;
const ll mod = 1000000007;
const int inf = (1 << 30) - 1;
const ll linf = 1LL << 60;
const double PI = 3.14159265358979323846;
mt19937 rng; // use it by rng() % mod, shuffle(all(vec), rng)
///////////////////////////////////////////////////////////////////////////////////////////////////

int N;
vector<int> G[210];
int d[210];

void solve() {
  cin >> N;
  rep(i, 0, N) {
    rep(j, 0, N) {
      char a;
      cin >> a;
      if (a == '1')
        G[i].pb(j);
    }
  }
  int res = 0;
  rep(q, 0, N) {
    fill(d, d + N, inf);
    d[q] = 0;
    queue<int> que;
    que.push(q);
    while (!que.empty()) {
      int v = que.front();
      que.pop();
      rep(i, 0, sz(G[v])) {
        int n = G[v][i];
        if (d[n] == inf) {
          d[n] = d[v] + 1;
          que.push(n);
        } else {
          if (d[n] % 2 == d[v] % 2) {
            cout << -1 << "\n";
            return;
          }
        }
      }
    }
    rep(i, 0, N) { MAX(res, d[i] + 1); }
  }
  cout << res << "\n";
}

uint32_t rd() {
  uint32_t res;
#ifdef __MINGW32__
  asm volatile("rdrand %0" : "=a"(res)::"cc");
#else
  res = std::random_device()();
#endif
  return res;
}

int main() {
#ifndef LOCAL
  ios::sync_with_stdio(false);
  cin.tie(0);
#endif
  cout << fixed;
  cout.precision(20);
  cerr << fixed;
  cerr.precision(6);
  rng.seed(rd());
#ifdef LOCAL
  // freopen("in.txt", "wt", stdout); //for tester
  if (!freopen("in.txt", "rt", stdin))
    return 1;
#endif
  solve();
  cerr << "Time: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
  return 0;
}