11 数值的整数次方

给定一个double类型的浮点数base和int类型的整数exponent。求base的exponent次方。

比如求2的32次方，先求出2的16次方，然后2^16 * 2^16
然后递归求2^16，如果次方为奇数，则再乘一个base

C++：

1 class Solution {
2 private:
3     bool invalidInput = false ;
4 public:
5     bool Equal(double num1 , double num2){
6         if ((num1-num2)<0.0000001 && (num1-num2)>-0.0000001)
7             return true ;
8         else
9             return false ;
10     }
11
12     double PowerWithUnsignedExponent(double base , int exponent){
13         if (exponent == 0)
14             return 1 ;
15         if (exponent == 1)
16             return base ;
17         double result = PowerWithUnsignedExponent(base,exponent>>1) ;
18         result *=result ;
19         if (exponent&1)
20             result *= base ;
21         return result ;
22     }
23
24     double Power(double base , int exponent){
25         bool invalidInput = false ;
26         if (Equal(base,0.0) && exponent < 0){
27             invalidInput = true ;
28             return 0.0 ;
29         }
30         int absExponent = abs(exponent) ;
31         double result = PowerWithUnsignedExponent(base,absExponent) ;
32         if (exponent < 0)
33             result = 1.0/result ;
34         return result ;
35     }
36 };