Problem p02991 (C++)

Buggy submission (status: Runtime Error):
#include "bits/stdc++.h"
using namespace std;
#define sim template <class c
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \
  sim > typename enable_if<sizeof dud<c>(0) x 1, debug &>::type operator<<(    \
            c i) {
sim > struct rge {
  c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << endl; }
  eni(!=) cerr << boolalpha << i;
  ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
  sim dor(const c &) { ris; }
#endif
}
;
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
#define cool                                                                   \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define int long long int
#define pb push_back
#define fe first
#define lb lower_bound
#define ub upper_bound
#define pii pair<pair<int, int>, pair<int, int>>
#define se second
#define endl "\n"
#define pi pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define bs binary_search
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rep1(i, a, b) for (int i = a; i <= b; i++)
#define all(c) (c).begin(), (c).end()
#define sz(x) (int)x.size()
#define PI 3.14159265358979323846

const int N = 1e5 + 5;

int mod = 1e9 + 7, INF = 1e17;

int dx[4] = {0, 0, +1, -1};
int dy[4] = {+1, -1, 0, 0};

vi v[N];
int d[N], vis[N];
int l, r;

void bfs(int x) {
  queue<int> q;
  q.push(x);
  vis[x] = 1;

  while (!q.empty()) {
    int nv = q.front();
    q.pop();

    for (auto to : v[nv]) {

      if (!vis[to]) {

        d[to] = d[nv] + 1;
        vis[to] = 1;
        q.push(to);
      }
    }
  }
}

void solve() {
  int n, m;
  cin >> n >> m;

  rep(i, 0, m) {

    int x, y;
    cin >> x >> y;

    v[x].pb(y + n);
    v[x + n].pb(y + 2 * n);
    v[x + 2 * n].pb(y);
  }

  cin >> l >> r;

  bfs(l);

  if (d[r] != 0 && d[r] % 3 == 0)
    cout << d[r] / 3 << endl;
  else
    cout << -1;
}

int32_t main() {
  cool;
  int t = 1;
  // cin>>t;
  while (t--)
    solve();

  return 0;
}


Fixed submission:
#include "bits/stdc++.h"
using namespace std;
#define sim template <class c
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \
  sim > typename enable_if<sizeof dud<c>(0) x 1, debug &>::type operator<<(    \
            c i) {
sim > struct rge {
  c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << endl; }
  eni(!=) cerr << boolalpha << i;
  ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
  sim dor(const c &) { ris; }
#endif
}
;
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
#define cool                                                                   \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define int long long int
#define pb push_back
#define fe first
#define lb lower_bound
#define ub upper_bound
#define pii pair<pair<int, int>, pair<int, int>>
#define se second
#define endl "\n"
#define pi pair<int, int>
#define vi vector<int>
#define vvi vector<vi>
#define bs binary_search
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rep1(i, a, b) for (int i = a; i <= b; i++)
#define all(c) (c).begin(), (c).end()
#define sz(x) (int)x.size()
#define PI 3.14159265358979323846

const int N = 3e5 + 5;

int mod = 1e9 + 7, INF = 1e17;

int dx[4] = {0, 0, +1, -1};
int dy[4] = {+1, -1, 0, 0};

vi v[N];
int d[N], vis[N];
int l, r;

void bfs(int x) {
  queue<int> q;
  q.push(x);
  vis[x] = 1;

  while (!q.empty()) {
    int nv = q.front();
    q.pop();

    for (auto to : v[nv]) {

      if (!vis[to]) {

        d[to] = d[nv] + 1;
        vis[to] = 1;
        q.push(to);
      }
    }
  }
}

void solve() {
  int n, m;
  cin >> n >> m;

  rep(i, 0, m) {

    int x, y;
    cin >> x >> y;

    v[x].pb(y + n);
    v[x + n].pb(y + 2 * n);
    v[x + 2 * n].pb(y);
  }

  cin >> l >> r;

  bfs(l);

  if (d[r] != 0 && d[r] % 3 == 0)
    cout << d[r] / 3 << endl;
  else
    cout << -1;
}

int32_t main() {
  cool;
  int t = 1;
  // cin>>t;
  while (t--)
    solve();

  return 0;
}