201803-2 碰撞的小球

封裝小球對象，屬性包括位置，方向（向右爲1，向左爲-1）。移動時pos += dir 就可以了；轉換方向就是 dir *= -1。記得在小球到達繩子邊界和與其他小球位置相同時要轉向。

奉上java滿分代碼

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main{
    private static int l;
    static class Ball{
        public int pos;
        public int dir;

        public Ball(int pos) {
            this.pos = pos;
            this.dir = 1;
        }

        public void move(){
            this.pos += dir;

            if(this.pos >= l || this.pos <= 0)
                this.turn();
        }

        public void turn(){
            this.dir *= -1;
        }
    }

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        String[] firstLine = scanner.nextLine().split(" ");
        int n = Integer.parseInt(firstLine[0]);
        l = Integer.parseInt(firstLine[1]);
        int t = Integer.parseInt(firstLine[2]);
        String[] secondLine = scanner.nextLine().split(" ");
        List<Ball> balls = new ArrayList<>();
        for(int i = 0; i < n; i++){
            int pos = Integer.parseInt(secondLine[i]);
            balls.add(new Ball(pos));
        }
        scanner.close();

        while (t > 0){
            for(Ball ball : balls)
                ball.move();
            for(Ball ballI : balls){
                for(Ball ballJ : balls){
                    if(ballI.equals(ballJ))
                        continue;
                    if(ballI.pos == ballJ.pos)
                        ballI.turn();
                }
            }
            t--;
        }

        for(Ball ball : balls){
            System.out.print(ball.pos + " ");
        }
    }
}