跟大佬混出来的二分法解法,牛顿啥的,我好像已经过了学数学的年纪了,看不懂。。。
不过决定道理都差不多,尤其是说明了小数范围的情况下
特别注意,当输入num小于一的时候,记得右边界必须设定为1才行

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String i = sc.nextLine();
            double num = Double.parseDouble(i);
            boolean f= num<0;
            if(f) num*=-1;
            double pow = pow(num);
            DecimalFormat df   = new DecimalFormat("######0.0");
            if(f){
                System.out.println("-"+df.format(pow));
            }else {
                System.out.println(df.format(pow));
            }
        }

    }

    //二分法
    static double pow(double num){
        if ( num == 0) {
            return 0;
        }
        double left =0;
        double right = num>1?num:1;
        double mid = (right+left)/2;
        while (Math.abs(mid * mid * mid - num)>0.01&&left<=right){
            if(mid * mid * mid>num){
                right=mid-0.1;
            }else {
                left=mid+0.1;
            }
            mid = (right+left)/2;
        }
        return left;
    }