题目描述： 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。

代码

• 解法1：

    public double Power(double base, int exponent) {
        double res = 1.0;
        if (exponent == 0) return res;
        if (exponent < 0) {
            base = 1.0 / base;
            exponent = -exponent;
        }
        for (int i = 0; i < exponent; i++) {
            res *= base;
        }
        return res;
    }

• 解法2：

    public double Power(double base, int exponent) {
  
        double result = 1.0;
        if (exponent == 0) return result;
        if (exponent == 1) return base;
  
        int n = Math.abs(exponent);
        while (n != 0) {
            if ((n & 1) == 1) {
                result *= base;
            }
            n >>= 1;
            base *= base;
        }
  
        if (exponent < 0) result = 1 / result * 1.0;
  
  
        return result;
    }
  

• 解法3： ```java public double Power(double base, int exponent) { double result = 0.0; if (exponent == 0) return 1.0; if (exponent == 1) return base;

    int ex = Math.abs(exponent);
    result = Power3(base, ex >> 1);
    result *= result;
  
    if ((exponent & 1) == 1) result *= base;
  
    if (exponent < 0) result = 1 / result * 1.0;
    return result;   }
  

```