一种改进的pow(x,y)

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

/*
This is a free Program, You can modify or redistribute it under the terms of GNU
*Description:一种改进的求整数x的y次幂
*Language: C++
*Development Environment: VC6.0
*Author: Wangzhicheng
*E-mail: [email protected]
*Date: 2012/10/14
*/

/*
核心方法是利用乘方的性质
当x求出,x^2=x*x,当x^2求出,x^4=(x^2)*(x^2) ,依次类推
*/

const int max=100000000;  //底数最大的数

class Power {
private:
	int base;       //底数
	int exponent;    //指数
	long result;    //存放结果
public:
	Power(int b,int e) {
		if(b<0 || b>=max) {
			cerr<<"底数应该大于等于0且小于"<<max<<endl;
			exit(1);
		}
		if(e<0 || e>max/10000) {
			cerr<<"指数应该大于等于0且小于"<<(max/10000)<<endl;
			exit(1);
		}
		base=b;
		exponent=e;
	}
	void power() {
		int result=1;
		power(exponent,result);
		setResult(result);
		show();
	}
	void power_common() {
		int i;
		int result=1;
		for(i=0;i<exponent;i++) {
			result=result*base;
		}
		setResult(result);
		show();
	}
	void show() {
		if(result<0) {
			cerr<<"结果溢出!"<<endl;
			result=0;
			return;
		}
		cout<<"power("<<base<<","<<exponent<<")="<<result<<endl;
	}
private:
	void setResult(int r) {
		result=r;
	}
	void power(int exponent,int &result) {
		int pre=1;     //前面值
		int temp=base;    //每一位对应的权值
		while(exponent) {
			if(exponent%2) {
				result=pre*temp;
				pre=result;
			}
			temp=temp*temp;
			exponent/=2;
		}
	}
};

void main() {
	srand(unsigned(time(0)));
	int i;
	int x,y;
	const int N=10;
	for(i=0;i<N;i++) {
		x=rand()%(N*N);
		y=rand()%N;
		Power power(x,y);
		power.power();
		power.power_common();
	}
}