题解 | 绕距

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        //输入起点坐标
        int x1 = in.nextInt();
        int y1 = in.nextInt();

        //输入终点坐标
        int x2 = in.nextInt();
        int y2 = in.nextInt();

        double de = Math.sqrt((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2));
        double dm = Math.sqrt((x1 - x2)*(x1 - x2)) + Math.sqrt((y1 - y2)*(y1 - y2));
        double out = Math.sqrt((de - dm)*(de - dm));
        System.out.printf("%.8f", out);

    }
}

平方、开根、差值绝对值都可以直接用java内置函数来做，平方是Math.pow(x,2) ，开根是 Math.sqrt(x)，差值绝对值是Math.abs(x1-x2)