[LeetCode] 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]

Analyse:

​

Solution:

class Solution { 
    
    func myPow(_ x: Double, _ n: Int) -> Double {
        var base = x;
        var pow = n;
    
        if pow == 0 {
            return 1;
        }
        else if pow < 0 {
            pow = -pow;
            base = 1/base;
        }
    
        if pow % 2 == 0 {
            return myPow(base * base, pow/2);
        }
        else {
            return base * myPow(base * base, pow/2);
        }
    }
}