数值的整数次方

5.00e-01f

注意：

1.当指数是负数的时候，可以先对指数求绝对值，然后算出次方的结果之后求倒数。

2.当底数是0，指数是负数的时候应做特殊处理。

3.判断两个浮点数是否相等不应该直接用==。

#include<cstdio>
#include<cstring>
#include<cstdlib>

bool g_InvalidInput = false;

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

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;
}


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;
}

int main()
{
    int n;
    scanf("%d",&n);
    double base;
    int exponent;
    while(n--)
    {
        scanf("%lf%d",&base,&exponent);
        double result = Power(base,exponent);
        if(g_InvalidInput)
            printf("INF\n");
        else
        {
            printf("%.2ef\n",result);
        }
    }
    return 0;
}

数值的整数次方

原文：http://blog.csdn.net/biluyang/article/details/44058079