剑指Offer系列---(14)数值的整数次方

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1.题目描述：

实现函数double Power(double base,int exponent)，求base的exponent次方。不得使用库函数，同时不需要考虑大数问题。

2.源代码：

//  Copyright (c) 2015年 skewrain. All rights reserved.#include <iostream>#include <stdio.h>using namespace std;//自以为题目简单的解法，不能处理负数和0。double Power1(double base,int exponent){    double result = 1.0;    for (int i=1; i<=exponent; i++) {        result *= base;    }    return result;}//全面但不够高效的解法，使用全局变量。bool g_InvalidInput = false;bool equal(double num1,double num2){    if((num1-num2 >-0.0000001)&&(num1-num2 <0.0000001))        return true;    else        return false;}double PowerWithUnsignedExponent1(double base,unsigned int exponent){    double result = 1.0;    for (int i=1; i<=exponent; i++) {        result *= base;    }    return result;}double Power2(double base,int exponent){    g_InvalidInput = false;        if(equal(base, 0.0) && exponent <0)    {        g_InvalidInput = true;        return 0.0;    }        unsigned int absExponent = (unsigned int)exponent;    if (exponent < 0) {        absExponent = (unsigned int)(-exponent);    }        double result = PowerWithUnsignedExponent1(base,absExponent);    if (exponent < 0) {        result = 1.0/result;    }    return result;}//全面而高效的解法double PowerWithUnsignedExponent2(double base,unsigned int exponent){    if (exponent == 0)        return 1;    if (exponent == 1)        return base;    //用右移运算符代替了除以2    double result = PowerWithUnsignedExponent2(base,exponent>>1);    result *= result;    //用位与运算符代替了求余运算符（%）来判断一个数是奇数还是偶数。    if((exponent & 0x1) == 1)        result *= base;    return result;}int main(int argc,char *argv[]){    int base,exponent;    cout<<"请输入基数:";    cin>>base;    cout<<"请输入指数:";    cin>>exponent;    cout<<base<<"的"<<exponent<<"次方的值为:"<<Power1(base,exponent)<<endl;    cout<<base<<"的"<<exponent<<"次方的值为:"<<Power2(base,exponent)<<endl;    return 0;}

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