leetcode解题-pow(x, n)

class (object):
    def myPow(self, x, n):
        """
        :type x: float
        :type n: int
        :rtype: float
        """
        if n == 0:
            return 1.0
        positive = n > 0
        n = abs(n)
        if n % 2 == 1:
            r = x * self.myPow(x, n - 1)
        else:
            r = self.myPow(x, n / 2)
            r = r * r
        return r if positive else 1 / r

class (object):
    def myPow(self, x, n):
        """
        :type x: float
        :type n: int
        :rtype: float
        """
        if n == 0:
            return 1.0
        if n < 0:
            return 1.0 / self.myPow(x, -n)
        left = x
        right = 1.0
        while n > 1:
            if n % 2 == 1:
                right *= left
            left *= left
            n /= 2
        return left * right