Day-16_Pow(x,n).py

'''
	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:
    def myPow(self, x, n):
        if abs(x) < 1e-40: return 0 
        if n == 0: return 1
        if n < 0: return self.myPow(1/x, -n)
        lower = self.myPow(x, n//2)
        if n % 2 == 0: return lower*lower
        if n % 2 == 1: return lower*lower*x