剑指offer——面试题16：数值的整数次方

 // 面试题16：数值的整数次方
 // 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。

 #include <iostream>
 #include <cmath>

 bool g_InvalidInput = false;
 bool equal(double num1, double num2);
 double PowerWithUnsignedExponent(double base, unsigned int exponent);

 double Power(double base, int exponent)
 {
     g_InvalidInput = false;

     if (equal(base, 0.0) && exponent < )
     {
         g_InvalidInput = true;
         return 0.0;
     }

     unsigned int absExponent = (unsigned int) (exponent);
     if (exponent < )
         absExponent = (unsigned int) (-exponent);

     double result = PowerWithUnsignedExponent(base, absExponent);
     if (exponent < )
         result = 1.0 / result;

     return result;
 }

 /*
 double PowerWithUnsignedExponent(double base, unsigned int exponent)
 {
     double result = 1.0;

     for (int i = 1; i <= exponent; ++i)
         result *= base;
     return result;
 }
 */

 double PowerWithUnsignedExponent(double base, unsigned int exponent)
 {
     if (exponent == )
         return ;
     if (exponent == )
         return base;

     double result = PowerWithUnsignedExponent(base, exponent >> );
     result *= result;
     if ((exponent & 0x1) == )
         result *= base;

     return result;
 }

 bool equal(double num1, double num2)
 {
     if ((num1 - num2 > -0.0000001) && (num1 - num2 < 0.0000001))
         return true;
     else
         return false;
 }

 // ====================测试代码====================
 void Test(const char* testName, double base, int exponent, double expectedResult, bool expectedFlag)
 {
     double result = Power(base, exponent);
     if (equal(result, expectedResult) && g_InvalidInput == expectedFlag)
         std::cout << testName << " passed" << std::endl;
     else
         std::cout << testName << " FAILED" << std::endl;
 }

 int main(int argc, char* argv[])
 {
     // 底数、指数都为正数
     Test("Test1", , , , false);

     // 底数为负数、指数为正数
     Test("Test2", -, , -, false);

     // 指数为负数
     Test("Test3", , -, 0.125, false);

     // 指数为0
     Test("Test4", , , , false);

     // 底数、指数都为0
     Test("Test5", , , , false);

     // 底数为0、指数为正数
     Test("Test6", , , , false);

     // 底数为0、指数为负数
     Test("Test7", , -, , true);

     return ;
 }

本人答案：

 #include"iostream"
 #include"stdio.h"
 #include"stdexcept"
 using namespace std;

 bool errorFlag=false;

 double GetPower(double base,int exponent)
 {
     if(exponent==)
         return 1.0;
     if(exponent==)
         return base;

     double result=GetPower(base,exponent>>);
     result*=result;
     if(exponent&)
         result*=base;
     return result;
 }

 bool Equal(double num1,double num2)
 {
     if((num1-num2)>-0.000001&&(num1-num2)<0.000001)
         return true;
     return false;
 }

 double Power(double base,int exponent)
 {
     errorFlag=false;
     double result=;
   //  cout<<exponent<<endl;
     if(Equal(base,)&&exponent<)
     {
         errorFlag=true;
         return ;
     }
     if(exponent<)
     {
         result=1.0/GetPower(base,-exponent);
     }
     else
     {
         result=GetPower(base,exponent);
     }
     return result;
 }

 void Test(char *testName,double base,int exponent,double expectResult,bool expectFlag)
 {
     //注意这里需要后判断flag，不然前面函数没执行，errorFlag值不会得到更新
     if(Equal(Power(base,exponent),expectResult)&&errorFlag==expectFlag)
     {
         cout<<testName<<":passed."<<endl;
     }
     else
     {
         cout<<testName<<":failed."<<endl;
     }
 }

 int main()
 {
     Test("Test1",-,-,0.25,false);
     Test("Test2",-,,-,false);
     Test("Test3",-,,,false);
     Test("Test4",,-,,true);
     Test("Test5",,,,false);
     Test("Test6",,,,false);
     Test("Test7",,,,false);
     Test("Test8",,-,0.5,false);
     Test("Test9",,,,false);
     return ;
 }