50. Pow(x, n)

import math
class Solution:
    def myPow(self, x: float, n: int) -> float:
        return math.pow(x,n)

class Solution:
    def myPow(self, x: float, n: int) -> float:
        res = 1
        if n == 0: 
            return 1
        elif n < 0: 
            x = 1/x
            n = -n
        cur = x
        k = n
        while (k > 0):
            if k % 2 == 1: 
                res *= cur
            cur *= cur
            k //= 2
        return res