牛客_求解立方根

求解立方根
https://www.nowcoder.com/practice/caf35ae421194a1090c22fe223357dca

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            solution(in);
        }
    }

    private static void solution(Scanner in){
        double val = in.nextDouble();
        double num = Math.abs(val);

        double result = getCubeRoot(num);
        
        if(val < 0){
            result = -result;
        }

        System.out.println(result);
    }

    /**
     * 二分法
     * @param num
     * @return
     */
    private static double getCubeRoot(double num){

        if(num == 0){
            return 0;
        }

        double l = 0.0;
        double r = 3.0;
        while(l+0.1 <= r){
            double mid = (l+r)/2;
            if(mid*mid*mid >= num) {
                r = mid;
            }else{
                l = mid;
            }
        }
        
        double result;
        l = Double.parseDouble(String.format("%.1f", l));
        r = Double.parseDouble(String.format("%.1f", r));

        if(Math.abs(num-l*l*l) <= Math.abs(num-r*r*r)){
            result = l;
        }else{
            result = r;
        }

        return result;
    }
}