Problem p02962 (C++)

Buggy submission (status: 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 *buildFail(const string &p) {
  int m = p.size();
  int *fail = new int[m + 1];
  int j = fail[0] = -1;
  for (int i = 1; i <= m; ++i) {
    while (j >= 0 && p[j] != p[i - 1])
      j = fail[j];
    fail[i] = ++j;
  }
  return fail;
}

vector<set<int>> e;
int num[200010];
int rec(int c) {
  if (num[c] < 0) {
    cout << -1 << endl;
    exit(0);
  }
  if (num[c])
    return num[c];
  if (!e[c].size())
    return num[c] = 0;

  num[c] = -1;
  return num[c] = rec(*e[c].begin()) + 1;
}

int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);

  string s, t;
  cin >> s >> t;
  int n = s.size(), m = t.size();
  int *fail = buildFail(t);
  e.resize(n);
  for (int i = 0, k = 0; i < n + m; ++i) {
    while (k >= 0 && t[k] != s[i % n])
      k = fail[k];
    if (++k >= m) {
      e[(i - m % n + n + 1) % n].insert((i + 1) % n);
      k = fail[k];
    }
  }
  // dbg(e);
  int ans = 0;
  rep(i, n) if (!num[i]) ans = max(ans, rec(i));
  cout << ans << endl;

  return 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 *buildFail(const string &p) {
  int m = p.size();
  int *fail = new int[m + 1];
  int j = fail[0] = -1;
  for (int i = 1; i <= m; ++i) {
    while (j >= 0 && p[j] != p[i - 1])
      j = fail[j];
    fail[i] = ++j;
  }
  return fail;
}

vector<set<int>> e;
int num[500010];
int rec(int c) {
  if (num[c] < 0) {
    cout << -1 << endl;
    exit(0);
  }
  if (num[c])
    return num[c];
  if (!e[c].size())
    return num[c] = 0;

  num[c] = -1;
  return num[c] = rec(*e[c].begin()) + 1;
}

int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);

  string s, t;
  cin >> s >> t;
  int n = s.size(), m = t.size();
  int *fail = buildFail(t);
  e.resize(n);
  for (int i = 0, k = 0; i < n + m; ++i) {
    while (k >= 0 && t[k] != s[i % n])
      k = fail[k];
    if (++k >= m) {
      e[(i - m % n + n + 1) % n].insert((i + 1) % n);
      k = fail[k];
    }
  }
  // dbg(e);
  int ans = 0;
  rep(i, n) if (!num[i]) ans = max(ans, rec(i));
  cout << ans << endl;

  return 0;
}