Problem p02782 (C++)

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

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << '\n';
  exit(0);
}
inline void no() {
  cout << "No" << '\n';
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
inline u64 xorshift() {
  static u64 x = 88172645463325252ull;
  x = x ^ (x << 7);
  return x = x ^ (x >> 9);
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void amin(T &x, T y) {
  if (x > y)
    x = y;
}
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> inline T bis(T ok, T ng, function<bool(T)> f, T eps = 1) {
  while (abs(ok - ng) > eps) {
    T mi = (ok + ng) / 2;
    (f(mi) ? ok : ng) = mi;
  }
  return ok;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long a) {
    x = a % mod;
    if (x < 0)
      x += mod;
  }
  ModInt &operator+=(ModInt that) {
    x = (x + that.x) % mod;
    return *this;
  }
  ModInt &operator-=(ModInt that) {
    x = (x + mod - that.x) % mod;
    return *this;
  }
  ModInt &operator*=(ModInt that) {
    x = (long long)x * that.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
  ModInt inverse() {
    int a = x, b = mod, u = 1, v = 0;
    while (b) {
      int t = a / b;
      a -= t * b;
      u -= t * v;
      swap(a, b);
      swap(u, v);
    }
    return ModInt(u);
  }
#define op(o, p)                                                               \
  ModInt operator o(ModInt that) { return ModInt(*this) p that; }
  op(+, +=) op(-, -=) op(*, *=) op(/, /=)
#undef op
      friend ostream &
      operator<<(ostream &os, ModInt m) {
    return os << m.x;
  }
};

using mint = ModInt<1000000007>;

template <typename T> struct ModCalc {
  vector<T> fac, finv;
  ModCalc(int max) {
    fac = vector<T>(max + 1);
    finv = vector<T>(max + 1);
    fac[0] = 1;
    reps(i, max) fac[i] = fac[i - 1] * i;
    finv[max] = (T)1 / fac[max];
    rreps(i, max) finv[i - 1] = finv[i] * i;
  }
  T com(int a, int b) {
    if (a < 0 || b < 0 || b > a)
      return 0;
    return fac[a] * finv[a - b] * finv[b];
  }
};

using mcalc = ModCalc<mint>;
auto mc = mcalc(200010);

void solve() {
  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  r2++, c2++;
  mint ans = 0;
  ans += mc.com(r2 + c2, r2);
  ans -= mc.com(r1 + c2, r1);
  ans -= mc.com(r2 + c1, r2);
  ans += mc.com(r1 + c1, r1);
  cout << ans << endl;
}


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

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() {
  cout << "Yes" << '\n';
  exit(0);
}
inline void no() {
  cout << "No" << '\n';
  exit(0);
}
inline i64 gcd(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  if (a % b == 0)
    return b;
  return gcd(b, a % b);
}
inline i64 lcm(i64 a, i64 b) {
  if (min(a, b) == 0)
    return max(a, b);
  return a / gcd(a, b) * b;
}
inline u64 xorshift() {
  static u64 x = 88172645463325252ull;
  x = x ^ (x << 7);
  return x = x ^ (x >> 9);
}
template <typename T>
class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T>
class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void amin(T &x, T y) {
  if (x > y)
    x = y;
}
template <typename T> inline T exp(T x, i64 n, T e = 1) {
  T r = e;
  while (n > 0) {
    if (n & 1)
      r *= x;
    x *= x;
    n >>= 1;
  }
  return r;
}
template <typename T> inline T bis(T ok, T ng, function<bool(T)> f, T eps = 1) {
  while (abs(ok - ng) > eps) {
    T mi = (ok + ng) / 2;
    (f(mi) ? ok : ng) = mi;
  }
  return ok;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  each(x, v) is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  rep(i, v.size()) {
    if (i)
      os << ' ';
    os << v[i];
  }
  return os;
}
void solve();
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(16);
  solve();
  return 0;
}

template <int mod> struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(long long a) {
    x = a % mod;
    if (x < 0)
      x += mod;
  }
  ModInt &operator+=(ModInt that) {
    x = (x + that.x) % mod;
    return *this;
  }
  ModInt &operator-=(ModInt that) {
    x = (x + mod - that.x) % mod;
    return *this;
  }
  ModInt &operator*=(ModInt that) {
    x = (long long)x * that.x % mod;
    return *this;
  }
  ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
  ModInt inverse() {
    int a = x, b = mod, u = 1, v = 0;
    while (b) {
      int t = a / b;
      a -= t * b;
      u -= t * v;
      swap(a, b);
      swap(u, v);
    }
    return ModInt(u);
  }
#define op(o, p)                                                               \
  ModInt operator o(ModInt that) { return ModInt(*this) p that; }
  op(+, +=) op(-, -=) op(*, *=) op(/, /=)
#undef op
      friend ostream &
      operator<<(ostream &os, ModInt m) {
    return os << m.x;
  }
};

using mint = ModInt<1000000007>;

template <typename T> struct ModCalc {
  vector<T> fac, finv;
  ModCalc(int max) {
    fac = vector<T>(max + 1);
    finv = vector<T>(max + 1);
    fac[0] = 1;
    reps(i, max) fac[i] = fac[i - 1] * i;
    finv[max] = (T)1 / fac[max];
    rreps(i, max) finv[i - 1] = finv[i] * i;
  }
  T com(int a, int b) {
    if (a < 0 || b < 0 || b > a)
      return 0;
    return fac[a] * finv[a - b] * finv[b];
  }
};

using mcalc = ModCalc<mint>;
auto mc = mcalc(2000010);

void solve() {
  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  r2++, c2++;
  mint ans = 0;
  ans += mc.com(r2 + c2, r2);
  ans -= mc.com(r1 + c2, r1);
  ans -= mc.com(r2 + c1, r2);
  ans += mc.com(r1 + c1, r1);
  cout << ans << endl;
}