結果

問題 No.978 Fibonacci Convolution Easy
ユーザー ei1333333
提出日時 2020-01-31 21:45:31
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 23 ms / 2,000 ms
コード長 4,253 bytes
コンパイル時間 2,177 ms
コンパイル使用メモリ 195,880 KB
最終ジャッジ日時 2025-01-08 20:58:19
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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ファイルパターン 結果
other AC * 21
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ソースコード

diff # 

#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;
//const int mod = 998244353;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}


static constexpr uint32_t mul_inv(uint32_t n, int e = 5, uint32_t x = 1) {
  return e == 0 ? x : mul_inv(n, e - 1, x * (2 - x * n));
}

template< uint32_t mod >
struct ModInt {
  using u32 = uint32_t;
  using u64 = uint64_t;

  static constexpr u32 inv = mul_inv(mod);
  static constexpr u32 r2 = -u64(mod) % mod;

  u32 x;

  ModInt() : x(0) {}

  ModInt(const u32 &x) : x(reduce(u64(x) * r2)) {}

  u32 reduce(const u64 &w) const {
    return u32(w >> 32) + mod - u32((u64(u32(w) * inv) * mod) >> 32);
  }

  ModInt &operator+=(const ModInt &p) {
    if(int(x += p.x - 2 * mod) < 0) x += 2 * mod;
    return *this;
  }

  ModInt &operator-=(const ModInt &p) {
    if(int(x -= p.x) < 0) x += 2 * mod;
    return *this;
  }

  ModInt &operator*=(const ModInt &p) {
    x = reduce(uint64_t(x) * p.x);
    return *this;
  }

  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }


  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

  bool operator==(const ModInt &p) const { return get() == p.get(); }

  bool operator!=(const ModInt &p) const { return get() != p.get(); }

  int get() const { return reduce(x) % mod; }

  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(*this);
    while(n > 0) {
      if(n & 1) ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }

  ModInt inverse() const {
    return pow(mod - 2);
  }

  friend ostream &operator<<(ostream &os, const ModInt &p) {
    return os << p.get();
  }

  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt< mod >(t);
    return (is);
  }

  static int get_mod() { return mod; }
};

using modint = ModInt< mod >;

int main() {
  int N, P;
  cin >> N >> P;
  vector< modint > S(N);
  S[0] = 0;
  S[1] = 1;
  for(int i = 2; i < N; i++) {
    S[i] = S[i - 1] * P + S[i - 2];
  }
  modint sum = 0, ret = 0;
  for(int i = 0; i < N; i++) {
    sum += S[i];
    ret += sum * S[i];
  }
  cout << ret << endl;
}
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