pks38rqfp/c.txt

#include <iostream>

using namespace std;
const double e = 2.718281828459;

double log(double x)
{
	long t = 0;
	while (x > 1)
	{
		x /= e;
		++t;
	}
	x = x - 1;
	double ret = 0;
	int k = 1;
	double temp;
	double c = 1;
	double xx = 1;
	while (1)
	{
		xx *= x;
		temp = c * xx / k;
		c *= -1;
		ret += temp;
		++k;
		if (temp > -0.00000001)
			break;
	}
	return ret + t;
}

int main()
{
	double a, x;				// 计算log(a,x);
	// 用ln(x)/ln(a)计算。
	
		cin >> a >> x;
		if (a <= 0 || x <= 0 || a == 1)
		{
			cout << "输入不正确！" << endl;
		}
		double ans = log(x) / log(a);
		cout << ans << endl;	// log(x)返回x的自然对数，使用虚include"cmath"或"math.h"。
	return 0;
}