#pragma once
#include "real.hpp"
#include <vector>

namespace algoim
{
class Factorial
{
public:
    static std::vector<real> cache;

    static real calculate(int n)
    {
        if (n == 0) return 1;
        if (cache.size() <= n) {
            for (int i = cache.size(); i <= n; ++i) cache.push_back(cache[i - 1] * i);
        }
        return cache[n];
    }
};

std::vector<real> Factorial::cache = {1}; // 。

} // namespace algoim