https://leetcode.com/problems/powx-n/
Implement pow(x, n), which calculates x raised to the power n (i.e. xn).
Example 1:
Input: x = 2.00000, n = 10 Output: 1024.00000 Example 2:
Input: x = 2.10000, n = 3 Output: 9.26100 Example 3:
Input: x = 2.00000, n = -2 Output: 0.25000 Explanation: 2-2 = 1/22 = 1/4 = 0.25
Constraints:
-100.0 < x < 100.0 -231 <= n <= 231-1 -104 <= xn <= 104