Problem p02370 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define int ll
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define PB push_back

const ll LLINF = (1LL << 60);
const int INF = (1LL << 30);
const int MOD = 1000000007;

template <typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template <typename T> bool IN(T a, T b, T x) { return a <= x && x < b; }
template <typename T> T ceil(T a, T b) { return a / b + !!(a % b); }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &a) {
  out << '(' << a.first << ',' << a.second << ')';
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &a) {
  out << '[';
  REP(i, a.size()) {
    out << a[i];
    if (i != a.size() - 1)
      out << ',';
  }
  out << ']';
  return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};

// VI tsort(VVI g) {
//   int n = g.size();
//   vector<bool> used(n, false);
//   vector<int> ans;
//
//   function<void(int)> dfs = [&](int u) {
//     if(used[u]) return;
//     used[u] = true;
//     for(auto& i: g[u]) dfs(i);
//     ans.push_back(u);
//   };
//
//   for(int i=0; i<n; ++i) dfs(i);
//   reverse(ans.begin(), ans.end());
//   return ans;
// }

VI tsort(VVI g) {
  const int n = g.size();
  VI h(n, 0);
  REP(i, n) for (int j : g[i]) h[j]++;

  stack<int> st;
  REP(i, n) if (h[i] == 0) st.push(i);

  VI ans;
  while (st.size()) {
    int i = st.top();
    st.pop();
    ans.push_back(i);
    for (auto &j : g[i]) {
      h[j]--;
      if (h[j] == 0)
        st.push(j);
    }
  }

  return ans;
}

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n, m;
  cin >> n >> m;
  VVI g(n, VI(0));
  REP(i, m) {
    int a, b;
    cin >> a >> b;
    g[a].PB(b);
  }

  VI ans = tsort(g);
  for (int i : ans)
    cout << i << endl;

  return 0;
}


Error: -11

Fixed submission:

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define int ll
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define PB push_back

const ll LLINF = (1LL << 60);
const int INF = (1LL << 30);
const int MOD = 1000000007;

template <typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template <typename T> bool IN(T a, T b, T x) { return a <= x && x < b; }
template <typename T> T ceil(T a, T b) { return a / b + !!(a % b); }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &a) {
  out << '(' << a.first << ',' << a.second << ')';
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &a) {
  out << '[';
  REP(i, a.size()) {
    out << a[i];
    if (i != a.size() - 1)
      out << ',';
  }
  out << ']';
  return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};

// VI tsort(VVI g) {
//   int n = g.size();
//   vector<bool> used(n, false);
//   vector<int> ans;
//
//   function<void(int)> dfs = [&](int u) {
//     if(used[u]) return;
//     used[u] = true;
//     for(auto& i: g[u]) dfs(i);
//     ans.push_back(u);
//   };
//
//   for(int i=0; i<n; ++i) dfs(i);
//   reverse(ans.begin(), ans.end());
//   return ans;
// }

VI tsort(VVI g) {
  const int n = g.size();
  VI h(n, 0);
  REP(i, n) for (int j : g[i]) h[j]++;

  stack<int> st;
  REP(i, n) if (h[i] == 0) st.push(i);

  VI ans;
  while (st.size()) {
    int i = st.top();
    st.pop();
    ans.push_back(i);
    for (auto &j : g[i]) {
      h[j]--;
      if (h[j] == 0)
        st.push(j);
    }
  }

  return ans;
}

signed main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n, m;
  cin >> n >> m;
  VVI g(n, VI(0));
  REP(i, m) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    g[a].PB(b);
    g[b].PB(a);
  }

  VI ans = tsort(g);
  for (int i : ans)
    cout << i + 1 << endl;

  return 0;
}