fps/sample-point-shift.hpp

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• Last update: 2023-08-31 20:44:07+09:00
• Include: #include "fps/sample-point-shift.hpp"

Depends on

• 多項式/形式的冪級数ライブラリ (fps/formal-power-series.hpp)
• modulo/binomial.hpp

Required by

• P-recursiveの高速計算 (fps/find-p-recursive.hpp)
• 多項式行列のprefix product (matrix/polynomial-matrix-prefix-prod.hpp)
• 階乗 $\mod p$ (modulo/factorial.hpp)

Verified with

• verify/verify-unit-test/p-recursive.test.cpp
• verify/verify-unit-test/polynomial-matrix-prod.test.cpp
• verify/verify-yosupo-fps/yosupo-factorial-p-recursive.test.cpp
• verify/verify-yosupo-fps/yosupo-factorial.test.cpp
• verify/verify-yosupo-fps/yosupo-sample-point-shift.test.cpp
• verify/verify-yuki/yuki-0502.test.cpp
• verify/verify-yuki/yuki-1533.test.cpp

Code

#pragma once

#include "../modulo/binomial.hpp"
#include "formal-power-series.hpp"

// input : y(0), y(1), ..., y(n - 1)
// output : y(t), y(t + 1), ..., y(t + m - 1)
// (if m is default, m = n)
template <typename mint>
FormalPowerSeries<mint> SamplePointShift(FormalPowerSeries<mint>& y, mint t,
                                         int m = -1) {
  if (m == -1) m = y.size();
  long long T = t.get();
  int k = (int)y.size() - 1;
  T %= mint::get_mod();
  if (T <= k) {
    FormalPowerSeries<mint> ret(m);
    int ptr = 0;
    for (int64_t i = T; i <= k and ptr < m; i++) {
      ret[ptr++] = y[i];
    }
    if (k + 1 < T + m) {
      auto suf = SamplePointShift<mint>(y, k + 1, m - ptr);
      for (int i = k + 1; i < T + m; i++) {
        ret[ptr++] = suf[i - (k + 1)];
      }
    }
    return ret;
  }
  if (T + m > mint::get_mod()) {
    auto pref = SamplePointShift<mint>(y, T, mint::get_mod() - T);
    auto suf = SamplePointShift<mint>(y, 0, m - pref.size());
    copy(begin(suf), end(suf), back_inserter(pref));
    return pref;
  }

  FormalPowerSeries<mint> finv(k + 1, 1), d(k + 1);
  for (int i = 2; i <= k; i++) finv[k] *= i;
  finv[k] = mint(1) / finv[k];
  for (int i = k; i >= 1; i--) finv[i - 1] = finv[i] * i;
  for (int i = 0; i <= k; i++) {
    d[i] = finv[i] * finv[k - i] * y[i];
    if ((k - i) & 1) d[i] = -d[i];
  }

  FormalPowerSeries<mint> h(m + k);
  for (int i = 0; i < m + k; i++) {
    h[i] = mint(1) / (T - k + i);
  }

  auto dh = d * h;

  FormalPowerSeries<mint> ret(m);
  mint cur = T;
  for (int i = 1; i <= k; i++) cur *= T - i;
  for (int i = 0; i < m; i++) {
    ret[i] = cur * dh[k + i];
    cur *= T + i + 1;
    cur *= h[i];
  }
  return ret;
}

#line 2 "fps/sample-point-shift.hpp"

#line 2 "modulo/binomial.hpp"

#include <cassert>
#include <type_traits>
#include <vector>
using namespace std;

// コンストラクタの MAX に 「C(n, r) や fac(n) でクエリを投げる最大の n 」
// を入れると倍速くらいになる
// mod を超えて前計算して 0 割りを踏むバグは対策済み
template <typename T>
struct Binomial {
  vector<T> f, g, h;
  Binomial(int MAX = 0) {
    assert(T::get_mod() != 0 && "Binomial<mint>()");
    f.resize(1, T{1});
    g.resize(1, T{1});
    h.resize(1, T{1});
    if (MAX > 0) extend(MAX + 1);
  }

  void extend(int m = -1) {
    int n = f.size();
    if (m == -1) m = n * 2;
    m = min<int>(m, T::get_mod());
    if (n >= m) return;
    f.resize(m);
    g.resize(m);
    h.resize(m);
    for (int i = n; i < m; i++) f[i] = f[i - 1] * T(i);
    g[m - 1] = f[m - 1].inverse();
    h[m - 1] = g[m - 1] * f[m - 2];
    for (int i = m - 2; i >= n; i--) {
      g[i] = g[i + 1] * T(i + 1);
      h[i] = g[i] * f[i - 1];
    }
  }

  T fac(int i) {
    if (i < 0) return T(0);
    while (i >= (int)f.size()) extend();
    return f[i];
  }

  T finv(int i) {
    if (i < 0) return T(0);
    while (i >= (int)g.size()) extend();
    return g[i];
  }

  T inv(int i) {
    if (i < 0) return -inv(-i);
    while (i >= (int)h.size()) extend();
    return h[i];
  }

  T C(int n, int r) {
    if (n < 0 || n < r || r < 0) return T(0);
    return fac(n) * finv(n - r) * finv(r);
  }

  inline T operator()(int n, int r) { return C(n, r); }

  template <typename I>
  T multinomial(const vector<I>& r) {
    static_assert(is_integral<I>::value == true);
    int n = 0;
    for (auto& x : r) {
      if (x < 0) return T(0);
      n += x;
    }
    T res = fac(n);
    for (auto& x : r) res *= finv(x);
    return res;
  }

  template <typename I>
  T operator()(const vector<I>& r) {
    return multinomial(r);
  }

  T C_naive(int n, int r) {
    if (n < 0 || n < r || r < 0) return T(0);
    T ret = T(1);
    r = min(r, n - r);
    for (int i = 1; i <= r; ++i) ret *= inv(i) * (n--);
    return ret;
  }

  T P(int n, int r) {
    if (n < 0 || n < r || r < 0) return T(0);
    return fac(n) * finv(n - r);
  }

  // [x^r] 1 / (1-x)^n
  T H(int n, int r) {
    if (n < 0 || r < 0) return T(0);
    return r == 0 ? 1 : C(n + r - 1, r);
  }
};
#line 2 "fps/formal-power-series.hpp"

template <typename mint>
struct FormalPowerSeries : vector<mint> {
  using vector<mint>::vector;
  using FPS = FormalPowerSeries;

  FPS &operator+=(const FPS &r) {
    if (r.size() > this->size()) this->resize(r.size());
    for (int i = 0; i < (int)r.size(); i++) (*this)[i] += r[i];
    return *this;
  }

  FPS &operator+=(const mint &r) {
    if (this->empty()) this->resize(1);
    (*this)[0] += r;
    return *this;
  }

  FPS &operator-=(const FPS &r) {
    if (r.size() > this->size()) this->resize(r.size());
    for (int i = 0; i < (int)r.size(); i++) (*this)[i] -= r[i];
    return *this;
  }

  FPS &operator-=(const mint &r) {
    if (this->empty()) this->resize(1);
    (*this)[0] -= r;
    return *this;
  }

  FPS &operator*=(const mint &v) {
    for (int k = 0; k < (int)this->size(); k++) (*this)[k] *= v;
    return *this;
  }

  FPS &operator/=(const FPS &r) {
    if (this->size() < r.size()) {
      this->clear();
      return *this;
    }
    int n = this->size() - r.size() + 1;
    if ((int)r.size() <= 64) {
      FPS f(*this), g(r);
      g.shrink();
      mint coeff = g.back().inverse();
      for (auto &x : g) x *= coeff;
      int deg = (int)f.size() - (int)g.size() + 1;
      int gs = g.size();
      FPS quo(deg);
      for (int i = deg - 1; i >= 0; i--) {
        quo[i] = f[i + gs - 1];
        for (int j = 0; j < gs; j++) f[i + j] -= quo[i] * g[j];
      }
      *this = quo * coeff;
      this->resize(n, mint(0));
      return *this;
    }
    return *this = ((*this).rev().pre(n) * r.rev().inv(n)).pre(n).rev();
  }

  FPS &operator%=(const FPS &r) {
    *this -= *this / r * r;
    shrink();
    return *this;
  }

  FPS operator+(const FPS &r) const { return FPS(*this) += r; }
  FPS operator+(const mint &v) const { return FPS(*this) += v; }
  FPS operator-(const FPS &r) const { return FPS(*this) -= r; }
  FPS operator-(const mint &v) const { return FPS(*this) -= v; }
  FPS operator*(const FPS &r) const { return FPS(*this) *= r; }
  FPS operator*(const mint &v) const { return FPS(*this) *= v; }
  FPS operator/(const FPS &r) const { return FPS(*this) /= r; }
  FPS operator%(const FPS &r) const { return FPS(*this) %= r; }
  FPS operator-() const {
    FPS ret(this->size());
    for (int i = 0; i < (int)this->size(); i++) ret[i] = -(*this)[i];
    return ret;
  }

  void shrink() {
    while (this->size() && this->back() == mint(0)) this->pop_back();
  }

  FPS rev() const {
    FPS ret(*this);
    reverse(begin(ret), end(ret));
    return ret;
  }

  FPS dot(FPS r) const {
    FPS ret(min(this->size(), r.size()));
    for (int i = 0; i < (int)ret.size(); i++) ret[i] = (*this)[i] * r[i];
    return ret;
  }

  // 前 sz 項を取ってくる。sz に足りない項は 0 埋めする
  FPS pre(int sz) const {
    FPS ret(begin(*this), begin(*this) + min((int)this->size(), sz));
    if ((int)ret.size() < sz) ret.resize(sz);
    return ret;
  }

  FPS operator>>(int sz) const {
    if ((int)this->size() <= sz) return {};
    FPS ret(*this);
    ret.erase(ret.begin(), ret.begin() + sz);
    return ret;
  }

  FPS operator<<(int sz) const {
    FPS ret(*this);
    ret.insert(ret.begin(), sz, mint(0));
    return ret;
  }

  FPS diff() const {
    const int n = (int)this->size();
    FPS ret(max(0, n - 1));
    mint one(1), coeff(1);
    for (int i = 1; i < n; i++) {
      ret[i - 1] = (*this)[i] * coeff;
      coeff += one;
    }
    return ret;
  }

  FPS integral() const {
    const int n = (int)this->size();
    FPS ret(n + 1);
    ret[0] = mint(0);
    if (n > 0) ret[1] = mint(1);
    auto mod = mint::get_mod();
    for (int i = 2; i <= n; i++) ret[i] = (-ret[mod % i]) * (mod / i);
    for (int i = 0; i < n; i++) ret[i + 1] *= (*this)[i];
    return ret;
  }

  mint eval(mint x) const {
    mint r = 0, w = 1;
    for (auto &v : *this) r += w * v, w *= x;
    return r;
  }

  FPS log(int deg = -1) const {
    assert(!(*this).empty() && (*this)[0] == mint(1));
    if (deg == -1) deg = (int)this->size();
    return (this->diff() * this->inv(deg)).pre(deg - 1).integral();
  }

  FPS pow(int64_t k, int deg = -1) const {
    const int n = (int)this->size();
    if (deg == -1) deg = n;
    if (k == 0) {
      FPS ret(deg);
      if (deg) ret[0] = 1;
      return ret;
    }
    for (int i = 0; i < n; i++) {
      if ((*this)[i] != mint(0)) {
        mint rev = mint(1) / (*this)[i];
        FPS ret = (((*this * rev) >> i).log(deg) * k).exp(deg);
        ret *= (*this)[i].pow(k);
        ret = (ret << (i * k)).pre(deg);
        if ((int)ret.size() < deg) ret.resize(deg, mint(0));
        return ret;
      }
      if (__int128_t(i + 1) * k >= deg) return FPS(deg, mint(0));
    }
    return FPS(deg, mint(0));
  }

  static void *ntt_ptr;
  static void set_fft();
  FPS &operator*=(const FPS &r);
  void ntt();
  void intt();
  void ntt_doubling();
  static int ntt_pr();
  FPS inv(int deg = -1) const;
  FPS exp(int deg = -1) const;
};
template <typename mint>
void *FormalPowerSeries<mint>::ntt_ptr = nullptr;

/**
 * @brief 多項式/形式的冪級数ライブラリ
 * @docs docs/fps/formal-power-series.md
 */
#line 5 "fps/sample-point-shift.hpp"

// input : y(0), y(1), ..., y(n - 1)
// output : y(t), y(t + 1), ..., y(t + m - 1)
// (if m is default, m = n)
template <typename mint>
FormalPowerSeries<mint> SamplePointShift(FormalPowerSeries<mint>& y, mint t,
                                         int m = -1) {
  if (m == -1) m = y.size();
  long long T = t.get();
  int k = (int)y.size() - 1;
  T %= mint::get_mod();
  if (T <= k) {
    FormalPowerSeries<mint> ret(m);
    int ptr = 0;
    for (int64_t i = T; i <= k and ptr < m; i++) {
      ret[ptr++] = y[i];
    }
    if (k + 1 < T + m) {
      auto suf = SamplePointShift<mint>(y, k + 1, m - ptr);
      for (int i = k + 1; i < T + m; i++) {
        ret[ptr++] = suf[i - (k + 1)];
      }
    }
    return ret;
  }
  if (T + m > mint::get_mod()) {
    auto pref = SamplePointShift<mint>(y, T, mint::get_mod() - T);
    auto suf = SamplePointShift<mint>(y, 0, m - pref.size());
    copy(begin(suf), end(suf), back_inserter(pref));
    return pref;
  }

  FormalPowerSeries<mint> finv(k + 1, 1), d(k + 1);
  for (int i = 2; i <= k; i++) finv[k] *= i;
  finv[k] = mint(1) / finv[k];
  for (int i = k; i >= 1; i--) finv[i - 1] = finv[i] * i;
  for (int i = 0; i <= k; i++) {
    d[i] = finv[i] * finv[k - i] * y[i];
    if ((k - i) & 1) d[i] = -d[i];
  }

  FormalPowerSeries<mint> h(m + k);
  for (int i = 0; i < m + k; i++) {
    h[i] = mint(1) / (T - k + i);
  }

  auto dh = d * h;

  FormalPowerSeries<mint> ret(m);
  mint cur = T;
  for (int i = 1; i <= k; i++) cur *= T - i;
  for (int i = 0; i < m; i++) {
    ret[i] = cur * dh[k + i];
    cur *= T + i + 1;
    cur *= h[i];
  }
  return ret;
}

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