Tifa's CP Library

:heavy_check_mark: fft (src/code/conv/fft.hpp)

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Code

#ifndef TIFALIBS_CONV_FFT
#define TIFALIBS_CONV_FFT

#include "../util/util.hpp"

namespace tifa_libs::math {

template <std::floating_point FP>
struct FFT {
  using C = std::complex<FP>;
  using data_t = C;

  explicit constexpr FFT() : rev(), w() {}

  constexpr u32 size() const { return (u32)rev.size(); }
  constexpr void bzr(u32 len) {
    u32 n = std::max<u32>(std::bit_ceil(len), 2);
    if (n == size()) return;
    rev.resize(n, 0);
    u32 k = (u32)(std::bit_width(n) - 1);
    for (u32 i = 0; i < n; ++i) rev[i] = (rev[i / 2] / 2) | ((i & 1) << (k - 1));
    w.resize(n);
    w[0].real(1);
    for (u32 i = 1; i < n; ++i) w[i] = {std::cos(TAU * (FP)i / (FP)n), std::sin(TAU * (FP)i / (FP)n)};
  }

  constexpr void dif(vec<C> &f, u32 n = 0) const {
    if (!n) n = size();
    if (f.size() < n) f.resize(n);
    assert(n <= size());
    for (u32 i = 0; i < n; ++i)
      if (i < rev[i]) std::swap(f[rev[i]], f[i]);
#pragma GCC diagnostic ignored "-Wsign-conversion"
    for (u32 i = 2, d = n / 2; i <= n; i *= 2, d /= 2)
      for (u32 j = 0; j < n; j += i) {
        auto l = f.begin() + j, r = f.begin() + j + i / 2;
        auto p = w.begin();
        for (u32 k = 0; k < i / 2; ++k, ++l, ++r, p += d) {
          C tmp = *r * *p;
          *r = *l - tmp;
          *l = *l + tmp;
        }
      }
#pragma GCC diagnostic warning "-Wsign-conversion"
  }
  constexpr void dit(vec<C> &f, u32 n = 0) const {
    if (!n) n = size();
    dif(f, n);
    for (u32 i = 0; i < n; ++i) f[i] /= (FP)n;
  }

 private:
  const FP TAU = std::acos((FP)-1.) * 2;

  vecu rev;
  vec<C> w;
};

}  // namespace tifa_libs::math

#endif
#line 1 "src/code/conv/fft.hpp"



#line 1 "src/code/util/util.hpp"



#include <bits/stdc++.h>

template <class T>
constexpr T abs(T x) { return x < 0 ? -x : x; }

using i8 = int8_t;
using i16 = int16_t;
using i32 = int32_t;
using i64 = int64_t;
using i128 = __int128_t;
using isz = ptrdiff_t;

using u8 = uint8_t;
using u16 = uint16_t;
using u32 = uint32_t;
using u64 = uint64_t;
using u128 = __uint128_t;
using usz = size_t;

using f32 = float;
using f64 = double;
using f128 = long double;

template <class T>
using ptt = std::pair<T, T>;
template <class T>
using pt3 = std::tuple<T, T, T>;
template <class T>
using pt4 = std::tuple<T, T, T, T>;

template <class T, usz N>
using arr = std::array<T, N>;
template <class T>
using vec = std::vector<T>;
template <class T>
using vvec = vec<vec<T>>;
template <class T>
using v3ec = vec<vvec<T>>;
template <class U, class T>
using vecp = vec<std::pair<U, T>>;
template <class U, class T>
using vvecp = vvec<std::pair<U, T>>;
template <class T>
using vecpt = vec<ptt<T>>;
template <class T>
using vvecpt = vvec<ptt<T>>;

template <class T, class C = std::less<T>>
using pq = std::priority_queue<T, vec<T>, C>;
template <class T>
using pqg = std::priority_queue<T, vec<T>, std::greater<T>>;

using strn = std::string;
using strnv = std::string_view;

using vecu = vec<u32>;
using vvecu = vvec<u32>;
using v3ecu = v3ec<u32>;
using vecu64 = vec<u64>;
using vecb = vec<bool>;
using vvecb = vvec<bool>;

#ifdef ONLINE_JUDGE
#undef assert
#define assert(x) 42
#endif

using namespace std::literals;

constexpr i8 operator""_i8(unsigned long long x) { return (i8)x; }
constexpr i16 operator""_i16(unsigned long long x) { return (i16)x; }
constexpr i32 operator""_i32(unsigned long long x) { return (i32)x; }
constexpr i64 operator""_i64(unsigned long long x) { return (i64)x; }
constexpr isz operator""_iz(unsigned long long x) { return (isz)x; }

constexpr u8 operator""_u8(unsigned long long x) { return (u8)x; }
constexpr u16 operator""_u16(unsigned long long x) { return (u16)x; }
constexpr u32 operator""_u32(unsigned long long x) { return (u32)x; }
constexpr u64 operator""_u64(unsigned long long x) { return (u64)x; }
constexpr usz operator""_uz(unsigned long long x) { return (usz)x; }

inline const auto fn_0 = [](auto&&...) {};


#line 5 "src/code/conv/fft.hpp"

namespace tifa_libs::math {

template <std::floating_point FP>
struct FFT {
  using C = std::complex<FP>;
  using data_t = C;

  explicit constexpr FFT() : rev(), w() {}

  constexpr u32 size() const { return (u32)rev.size(); }
  constexpr void bzr(u32 len) {
    u32 n = std::max<u32>(std::bit_ceil(len), 2);
    if (n == size()) return;
    rev.resize(n, 0);
    u32 k = (u32)(std::bit_width(n) - 1);
    for (u32 i = 0; i < n; ++i) rev[i] = (rev[i / 2] / 2) | ((i & 1) << (k - 1));
    w.resize(n);
    w[0].real(1);
    for (u32 i = 1; i < n; ++i) w[i] = {std::cos(TAU * (FP)i / (FP)n), std::sin(TAU * (FP)i / (FP)n)};
  }

  constexpr void dif(vec<C> &f, u32 n = 0) const {
    if (!n) n = size();
    if (f.size() < n) f.resize(n);
    assert(n <= size());
    for (u32 i = 0; i < n; ++i)
      if (i < rev[i]) std::swap(f[rev[i]], f[i]);
#pragma GCC diagnostic ignored "-Wsign-conversion"
    for (u32 i = 2, d = n / 2; i <= n; i *= 2, d /= 2)
      for (u32 j = 0; j < n; j += i) {
        auto l = f.begin() + j, r = f.begin() + j + i / 2;
        auto p = w.begin();
        for (u32 k = 0; k < i / 2; ++k, ++l, ++r, p += d) {
          C tmp = *r * *p;
          *r = *l - tmp;
          *l = *l + tmp;
        }
      }
#pragma GCC diagnostic warning "-Wsign-conversion"
  }
  constexpr void dit(vec<C> &f, u32 n = 0) const {
    if (!n) n = size();
    dif(f, n);
    for (u32 i = 0; i < n; ++i) f[i] /= (FP)n;
  }

 private:
  const FP TAU = std::acos((FP)-1.) * 2;

  vecu rev;
  vec<C> w;
};

}  // namespace tifa_libs::math


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