powx-n.py

# -*- coding:utf-8 -*-


# 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]
#
#


class Solution(object):
    def myPow(self, x, n):
        """
        :type x: float
        :type n: int
        :rtype: float
        """
        if not n:
            return 1
        if n < 0:
            return 1 / self.myPow(x, -n)
        if n % 2:
            return x * self.myPow(x, n-1)
        return self.myPow(x*x, n/2)