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):
         """
         :type x: float
         :type n: int
         :rtype: float
         """
         if n < 0:
             return 1 / self.powRecu(x, -n)
         
         return self.powRecu(x, n)
     
     def powRecu(self, x, n):
         if n == 0:
             return 1.0
         
         if n % 2 == 0:
             return self.powRecu(x * x, n // 2)
         else:
             return x * self.powRecu(x * x, n // 2)
class Solution:
     def myPow(self, x, n):
         """
         :type x: float
         :type n: int
         :rtype: float
         """
         if n < 0:
             return 1 / self.powRecu(x, -n)
         
         return self.powRecu(x, n)
     
     def powRecu(self, x, n):
         if n == 0:
             return 1.0
         
         if n % 2 == 0:
             return self.powRecu(x * x, n // 2)
         else:
             return x * self.powRecu(x * x, n // 2)