text: /*
  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)
    {
      long long N = abs(n);
      double ans = 1.0;
      while (N > 0)
      {
        if (N % 2 == 1)
        {
          ans = ans * x;
          N--;
        }
        else
        {
          x = x * x;
          N = N / 2;
        }
      }
  
      if (n < 0)
        return 1.0 / ans;
      else
        return ans;
    }
  };