Problem p02782 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for (int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

template <uint_fast64_t MOD> class ModInt {
  using u64 = uint_fast64_t;

public:
  u64 val;

  ModInt(const u64 x = 0) : val(x % MOD) {}
  constexpr u64 &value() { return val; }
  constexpr ModInt operator-() { return val ? MOD - val : 0; }
  constexpr ModInt operator+(const ModInt &rhs) const {
    return ModInt(*this) += rhs;
  }
  constexpr ModInt operator-(const ModInt &rhs) const {
    return ModInt(*this) -= rhs;
  }
  constexpr ModInt operator*(const ModInt &rhs) const {
    return ModInt(*this) *= rhs;
  }
  constexpr ModInt operator/(const ModInt &rhs) const {
    return ModInt(*this) /= rhs;
  }
  constexpr ModInt &operator+=(const ModInt &rhs) {
    val += rhs.val;
    if (val >= MOD) {
      val -= MOD;
    }
    return *this;
  }
  constexpr ModInt &operator-=(const ModInt &rhs) {
    if (val < rhs.val) {
      val += MOD;
    }
    val -= rhs.val;
    return *this;
  }
  constexpr ModInt &operator*=(const ModInt &rhs) {
    val = val * rhs.val % MOD;
    return *this;
  }

  constexpr ModInt &operator/=(const ModInt &rhs) {
    *this *= rhs.inv();
    return *this;
  }

  constexpr bool operator==(const ModInt &rhs) { return this->a == rhs.a; }
  constexpr bool operator!=(const ModInt &rhs) { return this->a != rhs.a; }
  friend constexpr ostream &operator<<(ostream &os, const ModInt<MOD> &x) {
    return os << x.val;
  }
  friend constexpr istream &operator>>(istream &is, ModInt<MOD> &x) {
    return is >> x.val;
  }

  constexpr ModInt inv() const {
    u64 x = val, y = MOD, u = 1, v = 0, t = 0;
    while (y > 0) {
      t = x / y;
      x -= t * y;
      swap(x, y);
      u -= t * v;
      swap(u, v);
    }
    return ModInt(u);
  }

  constexpr ModInt pow(int e) const {
    u64 x = 1, p = val;
    while (e > 0) {
      if (e % 2 == 0) {
        p = (p * p) % MOD;
        e /= 2;
      } else {
        x = (x * p) % MOD;
        e--;
      }
    }
    return ModInt(x);
  }
};

// 二項係数（nCk mod.p;1<=k<=n<=1e7,pは素数）for ModInt
template <class T> struct BiCoefficient {
  vector<T> fac, finv, inv;
  BiCoefficient(const int MAX) : fac(MAX), finv(MAX), inv(MAX) {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++) {
      fac[i] = fac[i - 1] * i;
      inv[i] = -inv[MOD % i] * (MOD / i);
      finv[i] = finv[i - 1] * inv[i];
    }
  }
  T comb(int n, int k) {
    if (n < k)
      return 0;
    if (n < 0 || k < 0)
      return 0;
    return fac[n] * finv[k] * finv[n - k];
  }
};

using mint = ModInt<MOD>;

int main() {
  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  BiCoefficient<mint> biCoef(1100000);
  auto f = [&](ll r, ll c) { return biCoef.comb(r + c, r); };
  mint res = 0;
  for (ll c = c1 + 1; c <= c2 + 1; c++) {
    res += f(r2, c) - f(r1 - 1, c);
  }
  cout << res << endl;
  return 0;
}

Fixed submission:
#include <algorithm>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for (int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

template <uint_fast64_t MOD> class ModInt {
  using u64 = uint_fast64_t;

public:
  u64 val;

  ModInt(const u64 x = 0) : val(x % MOD) {}
  constexpr u64 &value() { return val; }
  constexpr ModInt operator-() { return val ? MOD - val : 0; }
  constexpr ModInt operator+(const ModInt &rhs) const {
    return ModInt(*this) += rhs;
  }
  constexpr ModInt operator-(const ModInt &rhs) const {
    return ModInt(*this) -= rhs;
  }
  constexpr ModInt operator*(const ModInt &rhs) const {
    return ModInt(*this) *= rhs;
  }
  constexpr ModInt operator/(const ModInt &rhs) const {
    return ModInt(*this) /= rhs;
  }
  constexpr ModInt &operator+=(const ModInt &rhs) {
    val += rhs.val;
    if (val >= MOD) {
      val -= MOD;
    }
    return *this;
  }
  constexpr ModInt &operator-=(const ModInt &rhs) {
    if (val < rhs.val) {
      val += MOD;
    }
    val -= rhs.val;
    return *this;
  }
  constexpr ModInt &operator*=(const ModInt &rhs) {
    val = val * rhs.val % MOD;
    return *this;
  }

  constexpr ModInt &operator/=(const ModInt &rhs) {
    *this *= rhs.inv();
    return *this;
  }

  constexpr bool operator==(const ModInt &rhs) { return this->a == rhs.a; }
  constexpr bool operator!=(const ModInt &rhs) { return this->a != rhs.a; }
  friend constexpr ostream &operator<<(ostream &os, const ModInt<MOD> &x) {
    return os << x.val;
  }
  friend constexpr istream &operator>>(istream &is, ModInt<MOD> &x) {
    return is >> x.val;
  }

  constexpr ModInt inv() const {
    u64 x = val, y = MOD, u = 1, v = 0, t = 0;
    while (y > 0) {
      t = x / y;
      x -= t * y;
      swap(x, y);
      u -= t * v;
      swap(u, v);
    }
    return ModInt(u);
  }

  constexpr ModInt pow(int e) const {
    u64 x = 1, p = val;
    while (e > 0) {
      if (e % 2 == 0) {
        p = (p * p) % MOD;
        e /= 2;
      } else {
        x = (x * p) % MOD;
        e--;
      }
    }
    return ModInt(x);
  }
};

// 二項係数（nCk mod.p;1<=k<=n<=1e7,pは素数）for ModInt
template <class T> struct BiCoefficient {
  vector<T> fac, finv, inv;
  BiCoefficient(const int MAX) : fac(MAX), finv(MAX), inv(MAX) {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++) {
      fac[i] = fac[i - 1] * i;
      inv[i] = -inv[MOD % i] * (MOD / i);
      finv[i] = finv[i - 1] * inv[i];
    }
  }
  T comb(int n, int k) {
    if (n < k)
      return 0;
    if (n < 0 || k < 0)
      return 0;
    return fac[n] * finv[k] * finv[n - k];
  }
};

using mint = ModInt<MOD>;

int main() {
  int r1, c1, r2, c2;
  cin >> r1 >> c1 >> r2 >> c2;
  BiCoefficient<mint> biCoef(2100000);
  auto f = [&](ll r, ll c) { return biCoef.comb(r + c, r); };
  mint res = 0;
  for (ll c = c1 + 1; c <= c2 + 1; c++) {
    res += f(r2, c) - f(r1 - 1, c);
  }
  cout << res << endl;
  return 0;
}