Semifactorial
(Mylib/Combinatorics/semifactorial.cpp)

• View this file on GitHub
• Last update: 2021-04-23 23:44:44+09:00

Operations

Requirements

Notes

Problems

• F - Heights and Pairs

References

Code

#pragma once
#include <cassert>
#include <vector>

namespace haar_lib {
  template <typename T>
  class semifactorial {
  public:
    using value_type = T;

  private:
    int N_;
    std::vector<T> data_;

  public:
    semifactorial() {}
    semifactorial(int N) : N_(N), data_(N + 1, 1) {
      for (int i = 2; i <= N_; i += 2) data_[i] = data_[i - 2] * i;
      for (int i = 3; i <= N_; i += 2) data_[i] = data_[i - 2] * i;
    }

    T operator()(int i) const {
      assert(0 <= i and i <= N_);
      return data_[i];
    }
  };
}  // namespace haar_lib

#line 2 "Mylib/Combinatorics/semifactorial.cpp"
#include <cassert>
#include <vector>

namespace haar_lib {
  template <typename T>
  class semifactorial {
  public:
    using value_type = T;

  private:
    int N_;
    std::vector<T> data_;

  public:
    semifactorial() {}
    semifactorial(int N) : N_(N), data_(N + 1, 1) {
      for (int i = 2; i <= N_; i += 2) data_[i] = data_[i - 2] * i;
      for (int i = 3; i <= N_; i += 2) data_[i] = data_[i - 2] * i;
    }

    T operator()(int i) const {
      assert(0 <= i and i <= N_);
      return data_[i];
    }
  };
}  // namespace haar_lib

Back to top page