50.x的n次幂

leetcode

递归
时间复杂度 O(log n)
空间复杂度O(log n)

func myPow(x float64, n int) float64 {

    var helper func(float64, int) float64
    helper = func(x float64, n int) float64 {
        if n == 0 {
            return 1
        }

        temp := helper(x, n / 2)

        if n % 2 == 0 {
            temp = temp * temp
        } else {
            temp = temp * temp * x
        }

        return temp
    }

    if n < 0 {
        return 1 / helper(x, n)
    }
    
    return helper(x, n)    
}