面试题 11:数值的整数次方

一. 题目

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.

代码请到我的代码库中下载 Point2Offer

二. 代码

package ween_2;/**难度系数:*** * 剑指offer: 数值的整数次方 * 方法:考虑指数为负和底数为0 * 测试用例:功能测试(指数为正,指数为负,指数为0) * 特殊输入测试(底数为0) * @author dingding * Date:2017-6-22 17:00 * Declaration: All Rights Reserved! */public class No11 {    private static boolean invalidInput = false;    public static void main(String[] args) {        test1();        test2();        test3();        test4();    }    //计算    private static double power(double base,int exponent){        invalidInput = false;        if (equal(base,0.0) && exponent<0) {            invalidInput = true;            return 0.0;        }        int absExponent = exponent;        if (exponent<0) {            absExponent = -exponent;        }        double result = powerWithAbsExponent(base,absExponent);        if (exponent<0) {            result = 1.0/result;        }        return result;    }    //计算次方(使用递归方法,效率更高)    private static double powerWithAbsExponent(double base, int absExponent) {        if (absExponent==0) {            return 1;        }        if (absExponent==1) {            return base;        }        double result = powerWithAbsExponent(base, absExponent>>1);        result *=result;        if ((absExponent&1) == 1) {            result*=base;        }//      for (int i=1;i<=absExponent;i++){//          result*=base;//      }        return result;    }    //判断是否等于0    private static boolean equal(double a, double b) {        if ((a-b>-0.0000001)&&(a-b<0.0000001)) {            return true;        }else {            return false;                   }    }    private static void test1() {        double result = power(2, 4);        System.out.println(result);    }    private static void test2() {        double result = power(2, -3);        System.out.println(result);    }    private static void test3() {        double result = power(0, -1);        System.out.println(result);    }    private static void test4() {        double result = power(-2, 4);        System.out.println(result);    }}

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有不妥当之处,麻烦告知:D