50. Pow(x, n)

50. Pow(x, n)

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]

• Recursive Another option is to change x -> 1/x, n -> -n if n is negative at the very beginning.

  public double myPow(double x, int n) {
    if(n == 0) return 1;
    if(n == 1) return x;
    if(n == -1) return 1 / x;
    double divide = myPow(x, n / 2);
    double total = divide * divide;
    if(n % 2 != 0) total *= myPow(x, n % 2);
    return total;
  }