剑指 Offer 16. 数值的整数次方C语言 2021-4-20

#include "stdio.h"

unsigned int equalZero(double base, double zero)
{
    
    
    if ((base - zero > -0.000001) && (base - zero < 0.000001))
    {
    
    
        return 1;
    }

    return 0;
}

double PowerWithUnsigned(double base, unsigned int absExponent)
{
    
    
    if (absExponent == 0)
    {
    
    
        return 1;
    }
    if (absExponent == 1)
    {
    
    
        return base;
    }

    double result = PowerWithUnsigned(base, absExponent >> 1);
    result *= result;
    if (absExponent & 0x01 == 1)
    {
    
    
        result *= base;
    }
    printf("result:%f\n", result);
    return result;
}

unsigned int g_Invalid = 0;
double myPow(double base, int exponent)
{
    
    
    g_Invalid = 0;
    if (equalZero(base, 0.0) && exponent < 0)
    {
    
    
        printf("result:%d\n", __LINE__);
        g_Invalid = 1;
        return 0;
    }

    unsigned int absExponent = (unsigned int)exponent;
    if (exponent < 0)
    {
    
    
        /* 当-2147483648取绝对值时大于2147483647就会报错，所以先对负数进行强制类型转换。absExponent = labs(exponent);*/
        absExponent = (unsigned int)(-exponent);
    }

    double result = PowerWithUnsigned(base, absExponent);
    if (exponent < 0)
    {
    
    
        result = 1.0 / result;
        printf("result:%f\n", result);

    }

    return result;
}

int main()
{
    
    
    double base = 2;
    int exponent = -2;
    double result = myPow(base, exponent);
    printf("result:%f\n", result);
}