Problem p00316 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define dbg(...)                                                               \\
  do {                                                                         \\
    cerr << __LINE__ << ": ";                                                  \\
    dbgprint(#__VA_ARGS__, __VA_ARGS__);                                       \\
  } while (0);

using namespace std;

namespace std {
template <class S, class T> struct hash<pair<S, T>> {
  size_t operator()(const pair<S, T> &p) const {
    return ((size_t)1e9 + 7) * hash<S>()(p.first) + hash<T>()(p.second);
  }
};
template <class T> struct hash<vector<T>> {
  size_t operator()(const vector<T> &v) const {
    size_t h = 0;
    for (auto i : v)
      h = h * ((size_t)1e9 + 7) + hash<T>()(i) + 1;
    return h;
  }
};
} // namespace std
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "[ ";
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? " ]" : ", ");
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "{ ";
  for (const auto &i : v)
    os << i << ", ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &v) {
  os << "{";
  for (const auto &i : v)
    os << " " << i.first << ": " << i.second << ",";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
void dbgprint(const string &fmt) { cerr << endl; }
template <class H, class... T>
void dbgprint(const string &fmt, const H &h, const T &...r) {
  cerr << fmt.substr(0, fmt.find(",")) << "= " << h << " ";
  dbgprint(fmt.substr(fmt.find(",") + 1), r...);
}
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;

int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  int n, m, k;
  cin >> n >> m >> k;
  vi p(n + m);
  rep(i, n + m) p[i] = i;

  function<int(int)> root = [&](int x) {
    if (p[x] == x)
      return x;
    return p[x] = root(p[x]);
  };
  rep(it, k) {
    int a, b, c;
    cin >> a >> b >> c;
    b--;
    c--;
    if (a == 1) {
      int rb = root(b + m), rc = root(c + m);
      if (rb < m && rc < m && rb != rc) {
        cout << it + 1 << endl;
        return 0;
      }
      if (rb > rc)
        swap(rb, rc);
      p[rc] = rb;
    } else {
      int rb = root(b + m);
      if (rb < m && rb != c) {
        cout << it + 1 << endl;
        return 0;
      }
      p[rb] = c;
    }
    // if(it % 1000 == 999) rep(i, n + m) root(i);
  }
  cout << 0 << endl;
  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define dbg(...)                                                               \\
  do {                                                                         \\
    cerr << __LINE__ << ": ";                                                  \\
    dbgprint(#__VA_ARGS__, __VA_ARGS__);                                       \\
  } while (0);

using namespace std;

namespace std {
template <class S, class T> struct hash<pair<S, T>> {
  size_t operator()(const pair<S, T> &p) const {
    return ((size_t)1e9 + 7) * hash<S>()(p.first) + hash<T>()(p.second);
  }
};
template <class T> struct hash<vector<T>> {
  size_t operator()(const vector<T> &v) const {
    size_t h = 0;
    for (auto i : v)
      h = h * ((size_t)1e9 + 7) + hash<T>()(i) + 1;
    return h;
  }
};
} // namespace std
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "[ ";
  rep(i, v.size()) os << v[i] << (i == v.size() - 1 ? " ]" : ", ");
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &v) {
  os << "{ ";
  for (const auto &i : v)
    os << i << ", ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &v) {
  os << "{";
  for (const auto &i : v)
    os << " " << i.first << ": " << i.second << ",";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
void dbgprint(const string &fmt) { cerr << endl; }
template <class H, class... T>
void dbgprint(const string &fmt, const H &h, const T &...r) {
  cerr << fmt.substr(0, fmt.find(",")) << "= " << h << " ";
  dbgprint(fmt.substr(fmt.find(",") + 1), r...);
}
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pi;
const int inf = (int)1e9;
const double INF = 1e12, EPS = 1e-9;

int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  int n, m, k;
  cin >> n >> m >> k;
  vi p(n + m, -1);
  function<int(int)> root = [&](int x) {
    if (p[x] < 0)
      return x;
    return p[x] = root(p[x]);
  };
  rep(it, k) {
    int a, b, c;
    cin >> a >> b >> c;
    b--;
    c--;
    if (a == 1) {
      int rb = root(b + m), rc = root(c + m);
      if (rb < m && rc < m && rb != rc) {
        cout << it + 1 << endl;
        return 0;
      }
      if (rb > rc)
        swap(rb, rc);
      p[rc] = rb;
    } else {
      int rb = root(b + m);
      if (rb < m && rb != c) {
        cout << it + 1 << endl;
        return 0;
      }
      p[rb] = c;
    }
    if (it % 1000 == 999)
      rep(i, n + m) root(i);
  }
  cout << 0 << endl;
  return 0;
}