50. Pow(x, n) (MATH)

用二分法recursively的解决这道题 否则会有runtime error

 

class Solution {
    public double myPow(double x, int n) {
        if(n == 0) return 1;
        if(n < 0) { //注意MAX_INT < - MIN_INT 所以不能直接-n 否则会overflow
            x = 1 / x;
            return (n % 2 == 0) ? myPow(x * x, -(n / 2)) : x * myPow(x * x, -(n / 2));
        }
        return (n % 2 == 0) ? myPow(x * x, n / 2) : x * myPow(x * x, n / 2);
        
    }
}