Problem p02991 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<vector<ll>> VV;

#define REP(i, a, b) for (ll i = (a); i < (b); i++)
#define rep(i, n) REP(i, 0, n)
const int INF = 1e9;
const int MOD = 1000000007;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define ALL(v) v.begin(), v.end()
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define Each(a, b) for (auto &a : b)
#define REPM(i, mp) for (auto i = mp.begin(); i != mp.end(); ++i)
#define dbgmap(mp)                                                             \
  for (auto i = mp.begin(); i != mp.end(); ++i) {                              \
    cout << i->first << ":" << i->second << endl;                              \
  }
#define sum(v) accumulate(ALL(v), 0)
#define fi first
#define se second

template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}

// vector
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << "	";
  }
  return s;
}

// 2 dimentional vector
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &vv) {
  int len = vv.size();
  for (int i = 0; i < len; ++i) {
    s << vv[i] << endl;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, m, t, s;
  cin >> n >> m;
  VV graph(m + 1);
  rep(i, m) {
    ll a, b;
    cin >> a >> b;
    graph[a].pb(b);
  }
  cin >> s >> t;

  // i頂点に、aけんぱ余りbで到達。
  VV d(n + 1, Vec(3, INF));
  queue<tuple<ll, ll, ll>> q;

  // 地点、けんぱすう、余り
  q.push(make_tuple(s, 0, 0));
  while (!q.empty()) {
    tuple<ll, ll, ll> &tp = q.front();
    Vec &g = graph[get<0>(tp)];
    Each(child, g) {
      if (d[child][(get<2>(tp) + 1) % 3] <= get<1>(tp) + (get<2>(tp) + 1) / 3) {
        continue;
      }
      d[child][(get<2>(tp) + 1) % 3] = get<1>(tp) + (get<2>(tp) + 1) / 3;
      // dbg(d);
      q.push(make_tuple(child, get<1>(tp) + (get<2>(tp) + 1) / 3,
                        (get<2>(tp) + 1) % 3));
    }
    q.pop();
  }
  ll ans = d[t][0];
  if (ans == INF) {
    cout << -1 << endl;

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


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<vector<ll>> VV;

#define REP(i, a, b) for (ll i = (a); i < (b); i++)
#define rep(i, n) REP(i, 0, n)
const int INF = 1e9;
const int MOD = 1000000007;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define ALL(v) v.begin(), v.end()
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define Each(a, b) for (auto &a : b)
#define REPM(i, mp) for (auto i = mp.begin(); i != mp.end(); ++i)
#define dbgmap(mp)                                                             \
  for (auto i = mp.begin(); i != mp.end(); ++i) {                              \
    cout << i->first << ":" << i->second << endl;                              \
  }
#define sum(v) accumulate(ALL(v), 0)
#define fi first
#define se second

template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}

// vector
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << "	";
  }
  return s;
}

// 2 dimentional vector
template <typename T>
ostream &operator<<(ostream &s, const vector<vector<T>> &vv) {
  int len = vv.size();
  for (int i = 0; i < len; ++i) {
    s << vv[i] << endl;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, m, t, s;
  cin >> n >> m;
  VV graph(m + 10);
  rep(i, m) {
    ll a, b;
    cin >> a >> b;
    graph[a].pb(b);
  }
  cin >> s >> t;

  // i頂点に、aけんぱ余りbで到達。
  VV d(n + 1, Vec(3, INF));
  queue<tuple<ll, ll, ll>> q;

  // 地点、けんぱすう、余り
  q.push(make_tuple(s, 0, 0));
  while (!q.empty()) {
    tuple<ll, ll, ll> &tp = q.front();
    Vec &g = graph[get<0>(tp)];
    Each(child, g) {
      if (d[child][(get<2>(tp) + 1) % 3] <= get<1>(tp) + (get<2>(tp) + 1) / 3) {
        continue;
      }
      d[child][(get<2>(tp) + 1) % 3] = get<1>(tp) + (get<2>(tp) + 1) / 3;
      // dbg(d);
      q.push(make_tuple(child, get<1>(tp) + (get<2>(tp) + 1) / 3,
                        (get<2>(tp) + 1) % 3));
    }
    q.pop();
  }
  ll ans = d[t][0];
  if (ans == INF) {
    cout << -1 << endl;

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