Method helper

src/com/blankj/medium/_0050/Solution.java:17–23

(double x, int n)

    }

    private double helper(double x, int n) {
        if (n == 0) return 1;
        if (n == 1) return x;
        double d = helper(x, n >>> 1);
        if (n % 2 == 0) return d * d;
        return d * d * x;
    }

    public static void main(String[] args) {
        Solution solution = new Solution();