Problem p02782 (C++)

Buggy submission (status: Runtime Error):
#ifndef LOCAL
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,mmx,tune=native")
#endif // LOCAL

#define _SCL_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS

#pragma comment(linker, "/STACK:256000000")

// #define push_back pb
#define first x
#define second y

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <ciso646>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#ifdef LOCAL
// #include <vld.h>
#endif // LOCAL
using namespace std;

// typedef __int128_t ll;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef long double ld;

#define speedup                                                                \
  cout.tie(nullptr);                                                           \
  cin.tie(nullptr);                                                            \
  ios_base::sync_with_stdio(false)
#define coutdouble                                                             \
  cout << setprecision(20);                                                    \
  cout << fixed

#define all(v) (v).begin(), (v).end()
#define sz(v) (int)(v).size()

#ifdef LOCAL
mt19937 rd(57322);
#else
mt19937 rd((uint)chrono::steady_clock::now().time_since_epoch().count());
#endif
/*------CommentInInteractive--------*/
#ifndef LOCAL
#define endl '\n'
#endif // LOCAL
/*----------------------------------*/
const int INF = 1000 * 1000 * 1000 + 322;
const ll LLINF = 2LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL + 57;
constexpr uint MOD = 1000 * 1000 * 1000 + 7;
constexpr uint FFT_MOD = 998244353;
const int P1E6 = 1336337;
const int P1E3 = 1009;
const ll P1E14 = 100000000000031;
const ll P1E17 = 100000000000000003;
const ld PI = acosl(-1.); // 3.1415926535897932384626433832795
const ld EPS = 1e-9;
/*------------------------------------------------IO_OPERATORS---------------------------------------------*/
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const pair<T, U> &_p) {
  _out << _p.first << " " << _p.second;
  return _out;
}
template <typename T, typename U>
inline istream &operator>>(istream &_in, pair<T, U> &_p) {
  _in >> _p.first >> _p.second;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const vector<T> &_v) {
  if (_v.empty())
    return _out;
  _out << _v.front();
  for (auto _it = ++_v.begin(); _it != _v.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T> inline istream &operator>>(istream &_in, vector<T> &_v) {
  for (auto &_i : _v)
    _in >> _i;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const set<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const multiset<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_set<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_multiset<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const map<T, U> &_m) {
  if (_m.empty())
    return _out;
  _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->first << ": " << _it->second << ')';
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const unordered_map<T, U> &_m) {
  if (_m.empty())
    return _out;
  _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->first << ": " << _it->second << ')';
  return _out;
}
/*--------------------------------------------------IO_FILES-----------------------------------------------*/
const char *infile =
#ifdef LOCAL
    "input.txt"
#else
    ""
#endif // LOCAL
    ;
const char *outfile =
#ifdef LOCAL
    ""
#else
    ""
#endif // LOCAL
    ;

/*-------------------------------------------------ALLOCATOR----------------------------------------------*/
// #define ALLOC_LOCAL
#ifdef ALLOC_LOCAL
const int ML_ = 450;
char mem_[ML_ * 1024 * 1024];
size_t _ptr = 0, _magic = 21323400;
void *operator new(size_t cnt) {
  if (_ptr + cnt < sizeof mem_) {
    _ptr += cnt;
    return mem_ + _ptr - cnt;
  } else {
    assert(false);
    _ptr = cnt + _magic;
    return mem_ + _magic;
  }
}
void operator delete(void *) {}
#endif // ALLOC_LOCAL
/*-----------------------------------------------------MATH------------------------------------------------*/
inline ll gcd(ll a, ll b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline int pwm(ll xx, ll pow, int MD) {
  if (pow < 0) {
    pow = pow % (MD - 1) + MD - 1;
  }
  ll mlt = 1;
  while (pow) {
    if (pow & 1) {
      mlt *= xx;
      mlt %= MD;
    }
    xx *= xx;
    pow >>= 1;
    xx %= MD;
  }
  return (int)mlt;
}
inline ll gcdex(ll a, ll b, ll &x, ll &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  ll xx, yy;
  ll gc = gcdex(b, a % b, yy, xx);
  x = xx;
  y = yy - (a / b) * xx;
  return gc;
}
inline int inv(ll r, int _mod) { return pwm(r % _mod, _mod - 2, _mod); }
/*-----------------------------------------------------CODE------------------------------------------------*/

int add(int a, int b) {
  a += b;
  if (a >= MOD)
    a -= MOD;
  return a;
}

int sub(int a, int b) {
  a -= b;
  if (a < 0)
    a += MOD;
  return a;
}

const int N = 1000 * 1000 + 57;
int fct[N], ifct[N];

int f(int n, int k) {
  n += k;
  // c(n + 2, k + 1)
  return int(ll(fct[n + 2]) * ifct[k + 1] % MOD * ifct[n - k + 1] % MOD);
}

void solve() {
  fct[0] = 1;
  for (int i = 1; i < N; ++i) {
    fct[i] = int(ll(fct[i - 1]) * i % MOD);
  }
  ifct[N - 1] = inv(fct[N - 1], MOD);
  for (int i = N - 2; i >= 0; --i) {
    ifct[i] = int(ll(ifct[i + 1]) * (i + 1) % MOD);
  }

  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  --r1;
  --c1;
  cout << add(sub(sub(f(r2, c2), f(r1, c2)), f(r2, c1)), f(r1, c1)) << endl;
}

int main() {

  if (*infile != '\0')
    (void)freopen(infile, "r", stdin);
  if (*outfile != '\0')
    (void)freopen(outfile, "w", stdout);

  speedup;
  coutdouble;

  // int tst = 1;
  // srand(time(NULL));
  // cin >> tst;
  // scanf("%d", &tst);
  // while (tst-- > 0) {
  // while(true) {
  solve();
  // if ((tst & 0xF) == 0) {
  // cerr << "ok\n";
  // }
  // cerr << "/*-----------------*/\n";
  // }

#ifdef LOCAL
  cerr << "Time: " << (ld)clock() / CLOCKS_PER_SEC << endl;
  while (true)
    ;
#endif // LOCAL

  return 0;
}

Fixed submission:
#ifndef LOCAL
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,mmx,tune=native")
#endif // LOCAL

#define _SCL_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS

#pragma comment(linker, "/STACK:256000000")

// #define push_back pb
#define first x
#define second y

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <ciso646>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#ifdef LOCAL
// #include <vld.h>
#endif // LOCAL
using namespace std;

// typedef __int128_t ll;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef long double ld;

#define speedup                                                                \
  cout.tie(nullptr);                                                           \
  cin.tie(nullptr);                                                            \
  ios_base::sync_with_stdio(false)
#define coutdouble                                                             \
  cout << setprecision(20);                                                    \
  cout << fixed

#define all(v) (v).begin(), (v).end()
#define sz(v) (int)(v).size()

#ifdef LOCAL
mt19937 rd(57322);
#else
mt19937 rd((uint)chrono::steady_clock::now().time_since_epoch().count());
#endif
/*------CommentInInteractive--------*/
#ifndef LOCAL
#define endl '\n'
#endif // LOCAL
/*----------------------------------*/
const int INF = 1000 * 1000 * 1000 + 322;
const ll LLINF = 2LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL + 57;
constexpr uint MOD = 1000 * 1000 * 1000 + 7;
constexpr uint FFT_MOD = 998244353;
const int P1E6 = 1336337;
const int P1E3 = 1009;
const ll P1E14 = 100000000000031;
const ll P1E17 = 100000000000000003;
const ld PI = acosl(-1.); // 3.1415926535897932384626433832795
const ld EPS = 1e-9;
/*------------------------------------------------IO_OPERATORS---------------------------------------------*/
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const pair<T, U> &_p) {
  _out << _p.first << " " << _p.second;
  return _out;
}
template <typename T, typename U>
inline istream &operator>>(istream &_in, pair<T, U> &_p) {
  _in >> _p.first >> _p.second;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const vector<T> &_v) {
  if (_v.empty())
    return _out;
  _out << _v.front();
  for (auto _it = ++_v.begin(); _it != _v.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T> inline istream &operator>>(istream &_in, vector<T> &_v) {
  for (auto &_i : _v)
    _in >> _i;
  return _in;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const set<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const multiset<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_set<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T>
inline ostream &operator<<(ostream &_out, const unordered_multiset<T> &_s) {
  if (_s.empty())
    return _out;
  _out << *_s.begin();
  for (auto _it = ++_s.begin(); _it != _s.end(); ++_it)
    _out << ' ' << *_it;
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const map<T, U> &_m) {
  if (_m.empty())
    return _out;
  _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->first << ": " << _it->second << ')';
  return _out;
}
template <typename T, typename U>
inline ostream &operator<<(ostream &_out, const unordered_map<T, U> &_m) {
  if (_m.empty())
    return _out;
  _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')';
  for (auto _it = ++_m.begin(); _it != _m.end(); ++_it)
    _out << ", (" << _it->first << ": " << _it->second << ')';
  return _out;
}
/*--------------------------------------------------IO_FILES-----------------------------------------------*/
const char *infile =
#ifdef LOCAL
    "input.txt"
#else
    ""
#endif // LOCAL
    ;
const char *outfile =
#ifdef LOCAL
    ""
#else
    ""
#endif // LOCAL
    ;

/*-------------------------------------------------ALLOCATOR----------------------------------------------*/
// #define ALLOC_LOCAL
#ifdef ALLOC_LOCAL
const int ML_ = 450;
char mem_[ML_ * 1024 * 1024];
size_t _ptr = 0, _magic = 21323400;
void *operator new(size_t cnt) {
  if (_ptr + cnt < sizeof mem_) {
    _ptr += cnt;
    return mem_ + _ptr - cnt;
  } else {
    assert(false);
    _ptr = cnt + _magic;
    return mem_ + _magic;
  }
}
void operator delete(void *) {}
#endif // ALLOC_LOCAL
/*-----------------------------------------------------MATH------------------------------------------------*/
inline ll gcd(ll a, ll b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline int pwm(ll xx, ll pow, int MD) {
  if (pow < 0) {
    pow = pow % (MD - 1) + MD - 1;
  }
  ll mlt = 1;
  while (pow) {
    if (pow & 1) {
      mlt *= xx;
      mlt %= MD;
    }
    xx *= xx;
    pow >>= 1;
    xx %= MD;
  }
  return (int)mlt;
}
inline ll gcdex(ll a, ll b, ll &x, ll &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  ll xx, yy;
  ll gc = gcdex(b, a % b, yy, xx);
  x = xx;
  y = yy - (a / b) * xx;
  return gc;
}
inline int inv(ll r, int _mod) { return pwm(r % _mod, _mod - 2, _mod); }
/*-----------------------------------------------------CODE------------------------------------------------*/

int add(int a, int b) {
  a += b;
  if (a >= MOD)
    a -= MOD;
  return a;
}

int sub(int a, int b) {
  a -= b;
  if (a < 0)
    a += MOD;
  return a;
}

const int N = 2000 * 1000 + 57;
int fct[N], ifct[N];

int f(int n, int k) {
  n += k;
  // c(n + 2, k + 1)
  return int(ll(fct[n + 2]) * ifct[k + 1] % MOD * ifct[n - k + 1] % MOD);
}

void solve() {
  fct[0] = 1;
  for (int i = 1; i < N; ++i) {
    fct[i] = int(ll(fct[i - 1]) * i % MOD);
  }
  ifct[N - 1] = inv(fct[N - 1], MOD);
  for (int i = N - 2; i >= 0; --i) {
    ifct[i] = int(ll(ifct[i + 1]) * (i + 1) % MOD);
  }

  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  --r1;
  --c1;
  cout << add(sub(sub(f(r2, c2), f(r1, c2)), f(r2, c1)), f(r1, c1)) << endl;
}

int main() {

  if (*infile != '\0')
    (void)freopen(infile, "r", stdin);
  if (*outfile != '\0')
    (void)freopen(outfile, "w", stdout);

  speedup;
  coutdouble;

  // int tst = 1;
  // srand(time(NULL));
  // cin >> tst;
  // scanf("%d", &tst);
  // while (tst-- > 0) {
  // while(true) {
  solve();
  // if ((tst & 0xF) == 0) {
  // cerr << "ok\n";
  // }
  // cerr << "/*-----------------*/\n";
  // }

#ifdef LOCAL
  cerr << "Time: " << (ld)clock() / CLOCKS_PER_SEC << endl;
  while (true)
    ;
#endif // LOCAL

  return 0;
}