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143 lines (113 loc) · 3.37 KB
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#if 0
#include<iostream>
#include<cmath>
using namespace std;
#define eps 1e-6
double Power(double base, int exponent)
{
if(base - 0.0 < eps && base - 0.0 > -eps && exponent < 0)
return 0.0;
if(exponent == 0)
return 1.0;
if(exponent == 1)
return base;
double result = 1.0;
for(int i = 1; i <= abs(exponent); i++)
{
result *= base;
}
if(exponent < 0)
result = 1 / result;
return result;
}
#endif
/*******************************************************************
Copyright(c) 2016, Harry He
All rights reserved.
Distributed under the BSD license.
(See accompanying file LICENSE.txt at
https://github.com/zhedahht/CodingInterviewChinese2/blob/master/LICENSE.txt)
*******************************************************************/
//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》代码
// 作者：何海涛
//==================================================================
// 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 < 0)
{
g_InvalidInput = true;
return 0.0;
}
unsigned int absExponent = (unsigned int) (exponent);
if (exponent < 0)
absExponent = (unsigned int) (-exponent);
double result = PowerWithUnsignedExponent(base, absExponent);
if (exponent < 0)
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 == 0)
return 1;
if (exponent == 1)
return base;
double result = PowerWithUnsignedExponent(base, exponent >> 1);
result *= result;
if ((exponent & 0x1) == 1)
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", 2, 3, 8, false);
// 底数为负数、指数为正数
Test("Test2", -2, 3, -8, false);
// 指数为负数
Test("Test3", 2, -3, 0.125, false);
// 指数为0
Test("Test4", 2, 0, 1, false);
// 底数、指数都为0
Test("Test5", 0, 0, 1, false);
// 底数为0、指数为正数
Test("Test6", 0, 4, 0, false);
// 底数为0、指数为负数
Test("Test7", 0, -4, 0, true);
return 0;
}