Factorial
(src/combinatorics/factorial.hpp)

• View this file on GitHub
• Last update: 2021-10-09 12:38:59+09:00
• Include: #include "src/combinatorics/factorial.hpp"

Required by

• Binomial Coefficient (src/combinatorics/binomial.hpp)

Verified with

• test/aizu-online-judge/DPL_5_D.test.cpp

Code

#pragma once

/**
 * @file factorial.hpp
 * @brief Factorial
 */

#include <vector>

namespace workspace {

// Factorial.
template <class _Tp, class _X = int_least64_t> _Tp factorial(_X __x) noexcept {
  if (__x < 0) return 0;
  static std::vector<_Tp> __t{1};
  static size_t __i = (__t.reserve(0x1000000), 0);
  while (__i < size_t(__x)) __t.emplace_back(__t.back() * _Tp(++__i));
  return __t[__x];
}

// Inverse of factorial.
template <class _Tp, class _X = int_least64_t>
_Tp inverse_factorial(_X __x) noexcept {
  if (__x < 0) return 0;
  static std::vector<_Tp> __t{1};
  static size_t __i = (__t.reserve(0x1000000), 0);
  while (__i < size_t(__x)) __t.emplace_back(__t.back() / _Tp(++__i));
  return __t[__x];
}

}  // namespace workspace

#line 2 "src/combinatorics/factorial.hpp"

/**
 * @file factorial.hpp
 * @brief Factorial
 */

#include <vector>

namespace workspace {

// Factorial.
template <class _Tp, class _X = int_least64_t> _Tp factorial(_X __x) noexcept {
  if (__x < 0) return 0;
  static std::vector<_Tp> __t{1};
  static size_t __i = (__t.reserve(0x1000000), 0);
  while (__i < size_t(__x)) __t.emplace_back(__t.back() * _Tp(++__i));
  return __t[__x];
}

// Inverse of factorial.
template <class _Tp, class _X = int_least64_t>
_Tp inverse_factorial(_X __x) noexcept {
  if (__x < 0) return 0;
  static std::vector<_Tp> __t{1};
  static size_t __i = (__t.reserve(0x1000000), 0);
  while (__i < size_t(__x)) __t.emplace_back(__t.back() / _Tp(++__i));
  return __t[__x];
}

}  // namespace workspace

Back to top page