[轉]5只螞蟻的問題

題目：有一根27釐米的細木杆，在第3釐米、7釐米、11釐米、17釐米、23釐米這五個位置上各有一隻螞蟻。木杆很細，不能同時通過一隻螞蟻。開 始時，螞蟻的頭朝左還是朝右是任意的，它們只會朝前走或調頭，但不會後退。當任意兩隻螞蟻碰頭時，兩隻螞蟻會同時調頭朝反方向走。假設螞蟻們每秒鐘可以走 一釐米的距離。編寫程序，求所有螞蟻都離開木杆的最小時間和最大時間。

模擬每秒鐘5只螞蟻的情況。在生成Ant對象時確定螞蟻的運行方向和名字。代碼如下：

public class Ant {
    //螞蟻的位置
    private int position;
    //爬行方向
    private boolean front_flg;
    //是否到達終點
    private boolean isOver = false;
    //螞蟻的名字
    private String antName;
    public boolean isOver() {
        if((position == 0)||(position == 27)){
            isOver = true;
        } else {
            isOver = false;
        }
        return isOver;
    }
    public void setOver(boolean isOver) {
        this.isOver = isOver;
    }
    public String getAntName() {
        return antName;
    }
    public void setAntName(String antName) {
        this.antName = antName;
    }
    public boolean isFront_flg() {
        return front_flg;
    }
    public void setFront_flg(boolean front_flg) {
        this.front_flg = front_flg;
    }
    public void setPosition(int position) {
        this.position = position;
    }
    //構造方法
    public Ant (int position,boolean flg,String antName){
        this.position = position;
        this.front_flg = flg;
        this.antName = antName;
    }
    public void crawl(boolean front_flg){
        //根據爬行方向判斷position的加減
        if(!(isOver())){
            if (front_flg){
                position = position + 1;
            } else {
                position = position - 1;
            }
        }
        System.out.println(antName + " has arrived position : " + position);
    }
    public int getPosition() {
        return position;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Ant ant3 = new Ant (3,true,"ant3");
        Ant ant7 = new Ant (7,true,"ant7");
        Ant ant11 = new Ant (11,true,"ant11");
        Ant ant17 = new Ant (17,false,"ant17");
        Ant ant23 = new Ant (23,false,"ant23");
        //記錄爬行時間
        int useTime = 1;
        while(!(ant3.isOver()
                &&ant7.isOver()
                &&ant11.isOver()
                &&ant17.isOver()
                &&ant23.isOver())){

            //如果兩隻螞蟻相遇則調轉爬行方向
            if (ant3.getPosition()==ant7.getPosition()){
                boolean temp;
                temp = ant3.isFront_flg();
                ant3.setFront_flg(ant7.isFront_flg());
                ant7.setFront_flg(temp);
            }
            if (ant3.getPosition()==ant11.getPosition()){
                boolean temp;
                temp = ant3.isFront_flg();
                ant3.setFront_flg(ant11.isFront_flg());
                ant11.setFront_flg(temp);
            }
            if (ant3.getPosition()==ant17.getPosition()){
                boolean temp;
                temp = ant3.isFront_flg();
                ant3.setFront_flg(ant17.isFront_flg());
                ant17.setFront_flg(temp);
            }
            if (ant3.getPosition()==ant23.getPosition()){
                boolean temp;
                temp = ant3.isFront_flg();
                ant3.setFront_flg(ant23.isFront_flg());
                ant23.setFront_flg(temp);
            }

            if (ant7.getPosition()==ant11.getPosition()){
                boolean temp;
                temp = ant7.isFront_flg();
                ant7.setFront_flg(ant11.isFront_flg());
                ant11.setFront_flg(temp);
            }
            if (ant7.getPosition()==ant17.getPosition()){
                boolean temp;
                temp = ant7.isFront_flg();
                ant7.setFront_flg(ant17.isFront_flg());
                ant17.setFront_flg(temp);
            }
            if (ant7.getPosition()==ant23.getPosition()){
                boolean temp;
                temp = ant7.isFront_flg();
                ant7.setFront_flg(ant23.isFront_flg());
                ant23.setFront_flg(temp);
            }

            if (ant11.getPosition()==ant17.getPosition()){
                boolean temp;
                temp = ant11.isFront_flg();
                ant11.setFront_flg(ant17.isFront_flg());
                ant17.setFront_flg(temp);
            }
            if (ant11.getPosition()==ant23.getPosition()){
                boolean temp;
                temp = ant11.isFront_flg();
                ant11.setFront_flg(ant23.isFront_flg());
                ant23.setFront_flg(temp);
            }

            if (ant17.getPosition()==ant23.getPosition()){
                boolean temp;
                temp = ant17.isFront_flg();
                ant17.setFront_flg(ant23.isFront_flg());
                ant23.setFront_flg(temp);
            }
            //螞蟻爬行
            ant3.crawl(ant3.isFront_flg());            
            ant7.crawl(ant7.isFront_flg());            
            ant11.crawl(ant11.isFront_flg());            
            ant17.crawl(ant17.isFront_flg());            
            ant23.crawl(ant23.isFront_flg());            
            System.out.println("Use time is :" + useTime++);
            System.out.println("================================");
        }
    }
}