Math - 50. Pow(x, n)

50. Pow(x, n)

Implement pow(x, n), which calculates x raised to the power n (xn).

Example 1:

Input: 2.00000, 10
Output: 1024.00000

Example 2:

Input: 2.10000, 3
Output: 9.26100

Example 3:

Input: 2.00000, -2
Output: 0.25000
Explanation: 2^-2 = 1/22 = 1/4 = 0.25

Note:

• -100.0 < x < 100.0
• n is a 32-bit signed integer, within the range [−231, 231 − 1]

思路：

题目是让实现幂次计算，做法是把幂次分解，分解到0，然后乘起来，比如5^3 = 5^1 * 5^1 * 5^1 = (5^0 * 5^0 * 5^1) * (5^0 * 5^0 * 5^1)

代码：

go：

func myPow(x float64, n int) float64 {
    if n > 0 {
        return pow(x, n)
    } else {
        return 1.0 / pow(x, n)
    }
}

func pow(x float64, n int) float64 {
    if n == 0 {
        return 1
    }
    
    y := pow(x, n/2)
    if n % 2 == 0 {
        return y * y
    } else {
        return y * y * x
    }
}