practice.cpp

#include<iostream>
#include<boost/multiprecision/cpp_int.hpp>

//名前空間定義
namespace mp = boost::multiprecision;

mp::cpp_int multiply(mp::cpp_int& x,int y){
		mp::cpp_int tmp = 1;
		for (int i = 0; i < y; i++){
			tmp *= x;
		}
		return tmp;
};
mp::cpp_int kaijo(int x){
	mp::cpp_int tmp = 1;
	for (int i = 1; i < x+1; i++){
		tmp *= i;
	}
	return tmp;
};

int main(){
	mp::cpp_int ans = 1;
	mp::cpp_int ans_tmp = 1;//途中計算の答え
	mp::cpp_int temp_kaijo = 1;//階乗保存配列
	mp::cpp_int e_val = 1;//eの階乗
	for (unsigned int i = 1; i < 10; i++){
		if (i == 1){
			ans += 1;
		}
		else if (i == 2){
			ans += e_val;
		}
		else{
			ans += multiply(e_val, i - 1) / kaijo(i - 1);
		}
	}
	//e^x = 1 + x + x^2/2 + x^3/3! ...

	std::cout << ans << std::endl;
	getchar();
	return 0;
}