Pow(x, n).cpp

/*
Pow(x, 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
*/

class Solution
{
public:
  double myPow(double x, int n)
  {
    if (n == 0)
      return 1;
    double t = pow(x, n / 2);
    if (n % 2)
      return n < 0 ? 1 / x * t * t : x * t * t;
    else
      return t * t;
  }
};