Problem p00365 (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 main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  tuple<int, int, int> a, b, now;
  int x, y, z;
  cin >> x >> y >> z;
  a = tie(x, y, z);
  cin >> x >> y >> z;
  b = tie(x, y, z);
  if (a > b)
    swap(a, b);
  if (a == b) {
    cout << 0 << endl;
    return 0;
  }
  auto inc = [](tuple<int, int, int> &x) {
    auto numd = [](int y, int m) {
      const int a[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
      if (m != 2)
        return a[m - 1];
      if (y % 400 == 0 || y % 4 == 0 && y % 100)
        return 29;
      return 28;
    };

    int y, m, d;
    tie(y, m, d) = x;
    if (++d > numd(y, m)) {
      d = 1;
      if (++m > 12)
        m = 1, y++;
    }
    x = tie(y, m, d);
  };
  auto ok = [](tuple<int, int, int> b, tuple<int, int, int> a) {
    if (get<1>(a) == get<1>(b) && get<2>(a) == get<2>(b))
      return 1;
    if (get<1>(a) == 2 && get<2>(a) == 29 && get<1>(b) == 3 && get<2>(b) == 1 &&
        !(get<0>(b) % 400 == 0 || get<0>(b) % 4 == 0 && get<0>(b) % 100))
      return 1;
    return 0;
  };

  now = a;
  int ya = 0, yb = 0, ans = 0;
  while (now < b) {
    inc(now);
    if (ok(now, a))
      ya++;
    ans = max(ans, ya - yb);
  }
  dbg(get<0>(now), get<1>(now), get<2>(now));
  rep(it, 365 * 4400) {
    inc(now);
    if (ok(now, a))
      ya++;
    if (ok(now, b))
      yb++;
    ans = max(ans, ya - yb);
  }
  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 main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  tuple<int, int, int> a, b, now;
  int x, y, z;
  cin >> x >> y >> z;
  a = tie(x, y, z);
  cin >> x >> y >> z;
  b = tie(x, y, z);
  if (a > b)
    swap(a, b);
  if (a == b) {
    cout << 0 << endl;
    return 0;
  }
  auto inc = [](tuple<int, int, int> &x) {
    auto numd = [](int y, int m) {
      const int a[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
      if (m != 2)
        return a[m - 1];
      if (y % 400 == 0 || y % 4 == 0 && y % 100)
        return 29;
      return 28;
    };

    int y, m, d;
    tie(y, m, d) = x;
    if (++d > numd(y, m)) {
      d = 1;
      if (++m > 12)
        m = 1, y++;
    }
    x = tie(y, m, d);
  };
  auto ok = [](tuple<int, int, int> b, tuple<int, int, int> a) {
    if (get<1>(a) == get<1>(b) && get<2>(a) == get<2>(b))
      return 1;
    if (get<1>(a) == 2 && get<2>(a) == 29 && get<1>(b) == 3 && get<2>(b) == 1 &&
        !(get<0>(b) % 400 == 0 || get<0>(b) % 4 == 0 && get<0>(b) % 100))
      return 1;
    return 0;
  };

  now = a;
  int ya = 0, yb = 0, ans = 0;
  while (now < b) {
    inc(now);
    if (ok(now, a))
      ya++;
    ans = max(ans, ya - yb);
  }
  // dbg(get<0>(now),get<1>(now),get<2>(now));
  rep(it, 365 * 4400) {
    inc(now);
    if (ok(now, a))
      ya++;
    if (ok(now, b))
      yb++;
    ans = max(ans, ya - yb);
  }
  cout << ans << endl;

  return 0;
}