习题4_35阶乘问题

//Jiecheng.h
class Jiecheng
{
public :
	void Jiecheng_();//解决问题1
	void caculateE();//解决问题2
	void caculateEX();//解决问题3
	int test(int);//递归算法求阶乘
	double test_(double);//求阶乘的倒数
private:
	int N ;//计算到阶乘的最大位
	int I  ;//阶乘结果
};

 

//Jiecheng.cpp
#include "Jiecheng.h"
#include<iostream>
using namespace std;

int Jiecheng::test(int number)   //递归算法求阶乘 啊啊啊啊啊啊啊啊啊啊啊 啊啊
{
	if(number == 1) return 1;
	else 
		return number*test(number-1);
}

double Jiecheng::test_(double number)
{
	int final = test(static_cast<int>(number));
	return 1.00/(static_cast<double>(final));

}

void Jiecheng::Jiecheng_()
{
	cout << "问题一、请输入一个非负整数：";
	cin >> N ;
	
	while(N<0)    //至关重要额
	{
		cout << "阶乘中要求为非负数，请重新输入:";
		cin >> N ;
	}
	
	if(N>0)
	{
		cout << N << "! = " << test(N) << endl;
	}//end if
	else
	{
		cout << "0! = 1" << endl;
	}

}

void Jiecheng::caculateE()
{
	cout << "问题二、请输入一个正整数n：" ;
	cin  >> N ;

	while(N<=0)
	{
		cout << "题目要求N大于0，请重新输入N：" ;
		cin >> N;
	}

	double L = 1.00;   //L=e = 1 + 1/1! + 1/2! + 1/3! + 1/4! + ······
	for(double i=1.00;i<=static_cast<double>(N);i++)
	{
		L = L + test_(i);
	}
	cout << "e = " << L << endl;
}

void Jiecheng::caculateEX()
{
	int x ;
	cout << "问题三、请输入正整数N，以及e的系数x " ;
	cin >> N >> x ;
	while(N<=0)
	{
		cout << "题目要求N大于0，请重新输入N：" ;
		cin >> N;
	}
	double L = 1.00;//   exp(x)的解
	double y = 1.00;//每个项上的x
	int i=1;
	for(int i=1;i<=N;i++)
	{
		y = y*static_cast<double>(x) ;
		L =L +  y*test_(static_cast<double>(i)); //注意啊，是i循环，不是N不变啊，！！！！
	}
	cout << "e(" << x << ") = " << L << endl;; 
}

 

//caculate.cpp  /main.cpp
#include"Jiecheng.h"
#include<string>

int main()
{
	/*Jiecheng test1;
	test1.Jiecheng_();
	Jiecheng test2;
	test2.caculateE();*/
	Jiecheng test3;
	test3.caculateEX();
	system("pause >> cout ");
	return 0;
}