题解 | 绕距

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextInt()) { // 处理多组输入
            int x1 = in.nextInt();
            int y1 = in.nextInt();
            int x2 = in.nextInt();
            int y2 = in.nextInt();

            // 计算曼哈顿距离 dM
            double dM = Math.abs(x1 - x2) + Math.abs(y1 - y2);
            // 计算欧几里得距离 dE：先算平方和，再开根号
            double dx = x1 - x2;
            double dy = y1 - y2;
            double dE = Math.sqrt(dx * dx + dy * dy);
            // 计算绕距 delta
            double delta = Math.abs(dM - dE);

            // 输出结果（直接输出即可，系统会接受精度范围内的结果）
            System.out.println(delta);
        }
        in.close();
    }
}